opengl及osg中的几种渲染方法

glDrawArrays 和 glDrawElements 的作用都是从一个数据数组中提取数据渲染基本图元。( render primitives from array data )
 
 
注!如果要 glDrawArrays 和 glDrawElements 正确进行绘制的话,必须在之前 调用带有相应参数的 glEnableClientState 方法。 比如:

/* Enable vertex arrays. */
glEnableClientState( GL_VERTEX_ARRAY );
/* Enable texture arrays. */
glEnableClientState( GL_TEXTURE_COORD_ARRAY );


 
这两个方法的第一个形参都是代表 绘制模式(GLenum mode)。绘图模式有如下几种:
GL_POINTS
GL_LINES
GL_LINE_LOOP
GL_LINE_STRIP
GL_TRIANGLES
GL_TRIANGLE_STRIP
GL_TRIANGLE_FAN
 
我们还没有讨论点或线,所以我只介绍最后的三个 。
在我开始之前,我要提醒你,顶点数组可能包含不止一个三角形,以便当您只看到一个物体顶点数组,你要知道,不仅限于这一点。
 
假设我们有如下的顶点数据:

const GLfloat squareVertices[] = {
    -1.0,  1.0, -6.0,
// Top left
    -1.0, -1.0, -6.0,
// Bottom left
    1.0,  -1.0, -6.0,
// Bottom right
    1.0,   1.0, -6.
// Top right
};

 
GL_POINTS - 单独的将顶点画出来。
 
GL_LINES - 单独地将直线画出来。行为和 GL_TRIANGLES 类似。

GL_LINE_STRIP - 连贯地将直线画出来。行为和 GL_TRIANGLE_STRIP 类似。
 
GL_LINE_LOOP - 连贯地将直线画出来。行为和 GL_LINE_STRIP 类似,但是会自动将最后一个顶点和第一个顶点通过直线连接起来。
 
GL_TRIANGLES - 这个参数意味着OpenGL使用三个顶点来组成图形。所以,在开始的三个顶点,将用顶点1,顶点2,顶点3来组成一个三角形。完成后,在用下一组的三个顶点(顶点4,5,6)来组成三角形,直到数组结束。

 
GL_TRIANGLE_STRIP - OpenGL的使用将最开始的两个顶点出发,然后遍历每个顶点,这些顶点将使用前2个顶点一起组成一个三角形。
所以 squareVertices[6~8]{1.0, -1.0, 6.0} 将与 squareVerticies[0~2]{-1.0, 1.0, -6.0} 和 squareVerticies[3~5]{-1.0, -1.0, -6.0} 生成一个三角形。
squareVertices[9~11]{1.0, 1,0, -6.0} 将与  squareVertices[3~5]{-1.0, -1.0, -6.0} 和squareVertices[6~8]{1.0, -1.0, 6.0} 生成三角形。
 
也就是说,P0,P1,P2这三个点组成一个三角形,P1,P2,P3这三个点也组成一个三角形。
 
注意的是, squareVerticies[0~2]表示的意思是:
squareVerticies[0] x坐标
squareVerticies[1] y坐标
squareVerticies[2] z坐标
 
 
GL_TRIANGLE_FAN - 在跳过开始的2个顶点,然后遍历每个顶点,让OpenGL将这些顶点于它们前一个,以及数组的第一个顶点一起组成一个三角形。 squareVertices[6~8]{1.0, -1.0, 6.0} 将与 squareVerticies[3~5]{-1.0, -1.0, -6.0} (前一个)和 squareVerticies[0~2]{-1.0, 1.0, -6.0}(第一个).生成一个三角形。
 
也就是说,同样是P0,P1,P2,P3 这4个顶点。
1) 在 GL_TRIANGLE_STRIP 状态下是: P2、P1、P0 ; P3、P2、P1 这2个三角形。
2) 在 GL_TRIANGLE_FAN   状态下是: P2、P1、P0 ; P3、P2、P0 这2个三角形。
 
 
 
1.1 glDrawArrays 方法介绍
 
Description

glDrawArrays specifies multiple geometric primitives with very few subroutine calls. You can prespecify separate arrays of vertices, normals, colors, and texture coordinates and use them to construct a sequence of primitives with a single call to glDrawArrays.
 
When glDrawArrays is called, it uses count sequential elements from each enabled array to construct a sequence of geometric primitives, beginning with element first. mode specifies what kind of primitives are constructed, and how the array elements construct those primitives. If GL_VERTEX_ARRAY is not enabled, no geometric primitives are generated.
 
Vertex attributes that are modified by glDrawArrays have an unspecified value after glDrawArrays returns. For example, if GL_COLOR_ARRAY is enabled, the value of the current color is undefined after glDrawArrays executes. Attributes that aren't modified remain well defined.


示例代码:

glEnableClientState(GL_VERTEX_ARRAY);
    
const GLfixed vers[] = {
        F2X(0.25), F2X(0.25), F2X(0.0), 
        F2X(0.75), F2X(0.25), F2X(0.0), 
        F2X(0.25), F2X(0.75), F2X(0.0), 
        F2X(0.75), F2X(0.75), F2X(0.0), 
}
;

glVertexPointer(3, GL_FIXED, 0, vers);
    
glDrawArrays(GL_LINE_STRIP, 0, 4);
    
eglSwapBuffers(iGlDisp, iGlSurface);



结果:

 
 
1.2 glDrawElements 是一个OPENGL的图元绘制函数,从数组中获得数据并渲染图元。
函数原型为:
void glDrawElements(
        GLenum mode,
        GLsizei count,
        GLenum type,
        const GLvoid *indices
        );
其中:
    mode 指定绘制图元的类型,但是如果GL_VERTEX_ARRAY 没有被激活的话,不能生成任何图元。它应该是下列值之一:
        GL_POINTS, GL_LINE_STRIP,
        GL_LINE_LOOP, GL_LINES,
        GL_TRIANGLE_STRIP,
        GL_TRIANGLE_FAN,
        GL_TRIANGLES,
        GL_QUAD_STRIP,
        GL_QUADS,
        GL_POLYGON

        
    count 为绘制图元的数量。
    type 为索引数组(indices)中元素的类型,只能是下列值之一:
        GL_UNSIGNED_BYTE,
        GL_UNSIGNED_SHORT,
        GL_UNSIGNED_INT

       
    indices:指向索引数组的指针。

glDrawElements函数能够通过较少的函数调用绘制多个几何图元,而不是通过OPENGL函数调用来传递每一个顶点,法线,颜色信息。
 
你可以事先准备一系列分离的顶点、法线、颜色数组,并且调用一次glDrawElements把这些数组定义成一个图元序列。
 
当调用glDrawElements函数的时候,它将通过索引使用count个成序列的元素来创建一系列的几何图元。
 
glDrawElements修改的顶点属性在glDrawElements调用返回后的值具有不确定性。

例如,在 GL_COLOR_ARRAY 被激活后,当glDrawElements执行完成时,当前的颜色值是没有指定的。没有被修改的属性值保持不变。
 
可以在显示列表中包含 glDrawElements,当glDrawElements被包含进显示列表时,相应的顶点、法线、颜色数组数据也得进入显示列表的,因为那些数组指针是ClientSideState的变量,在显示列表创建的时候而不是在显示列表执行的时候,这些数组指针的值影响显示列表。
 
glDrawElements 只能用在 OPENGL1.1 或者更高的版本。

示例代码如下:

// The vertex array is enabled for writing and used during rendering.
glEnableClientState(GL_VERTEX_ARRAY);

// 顶点坐标数组
const GLfixed vers[] = {
        F2X(0.25), F2X(0.25), F2X(0.0),
// 第1个顶点坐标
        F2X(0.75), F2X(0.25), F2X(0.0),
// 第2个顶点坐标
        F2X(0.25), F2X(0.75), F2X(0.0),
// 第3个顶点坐标
        F2X(0.75), F2X(0.75), F2X(0.0) 
// 第4个顶点坐标
};


glVertexPointer(
        3,        
// 表示每一个顶点由3维坐标构成
        GL_FIXED,
// 顶点坐标数组中的元素是 GL_FIXED 类型
        0,       
// 从顶点坐标数组的第0个元素开始读取数据
        vers      
// 指向顶点坐标数组的指针
        );

// 等效替换 glDrawArrays(GL_TRIANGLE_STRIP, 0, 4) ++

/* 索引数组. 此索引数组表示依次是
第0个顶点{F2X(0.25), F2X(0.25), F2X(0.0)},
第1个顶点{F2X(0.75), F2X(0.25), F2X(0.0)},
第2个顶点{F2X(0.25), F2X(0.75), F2X(0.0)},
第3个顶点{F2X(0.75), F2X(0.75), F2X(0.0)} */

const GLubyte indices[] = {0, 1, 2, 3};

glDrawElements(
        GL_TRIANGLE_STRIP,
// 绘图模式
        4,                
// 依次从索引数组中读取4个顶点来进行绘制
        GL_UNSIGNED_BYTE, 
// 索引数组中存放的元素的类型
        indices           
// 指向索引数组的指针
        );

// 等效替换 glDrawArrays(GL_TRIANGLE_STRIP, 0, 4) --


eglSwapBuffers(iGlDisp, iGlSurface);

 

OpenGL VBO并不难,但是较繁琐,其实其概念跟加载纹理是一样的:

初始化阶段:
1. glGenBuffersARB(1, &nVBOVertices); //生成一个句柄
2. glBindBufferARB(GL_ARRAY_BUFFER_ARB, nVBOVertices); //声明该句柄为一个vbo句柄,并选择之
3. glBufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(vertices), vertices,GL_STATIC_DRAW); //将顶点集上传至server端

使用阶段:
1. glEnableClientState(GL_VERTEX_ARRAY); //开始使用vbo
2. glBindBufferARB(GL_ARRAY_BUFFER_ARB, nVBOVertices);  //选择当前使用的vbo
3. glVertexPointer(3, GL_FLOAT, 0, BUFFER_OFFSET(0));  //指定vbo顶点格式
4. glDrawArrays( GL_TRIANGLES, 0, g_pMesh->m_nVertexCount ); //画吧
5. glDisableClientState(GL_VERTEX_ARRAY); //停止使用vbo

收尾阶段:
1. glDeleteBuffersARB(1,&nVBOVertices); //删除句柄,同时删除server端顶点缓冲

再来看看纹理缓冲是怎么使用的,其实差不多:

初始化阶段:
1. glGenTextures(1, &texID);//创建句柄
2. glBindTexture(GL_TEXTURE_2D, texID); //设置句柄类型
3. glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img->GetWidth(), img->GetHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, raw_rgba); //上传纹理缓冲

使用阶段:
1. glEnable(GL_TEXTURE_2D); //开始使用纹理缓冲
2. glBindTexture(GL_TEXTURE_2D, texID); //选择当前使用的纹理缓冲
3. 发送顶点和纹理坐标,画吧...省略
4. glDisable(GL_TEXTURE_2D); //停止使用纹理

收尾阶段:
1. glDeleteTextures(1,&texID);//删除句柄,,同时删除server端缓冲

看到了么,这个概念是不是很相似?都是:

1. 创建句柄
2. 设置句柄类型
3. 上传数据
4. 开始使用缓冲
5. 选择句柄
6. 使用缓冲
7. 停止使用缓冲
8. 删除句柄和缓冲

 

 

 

 

void Geometry::drawImplementation(RenderInfo& renderInfo) const
{
    State& state = *renderInfo.getState();

//    unsigned int contextID = state.getContextID();
   
    // osg::notify(osg::NOTICE)<<"Geometry::drawImplementation"<<std::endl;

    if (_internalOptimizedGeometry.valid())
    {
        _internalOptimizedGeometry->drawImplementation(renderInfo);
        return;
    }

    const Extensions* extensions = getExtensions(state.getContextID(),true);

    if( !( ( _vertexData.array.valid() && _vertexData.array->getNumElements() != 0 ) ||
           ( _vertexAttribList.size() > 0 &&
             _vertexAttribList[0].array.valid() &&
             _vertexAttribList[0].array->getNumElements() != 0 ) ) )
    {
        return;
    }

    if( ( _vertexData.indices.valid() && _vertexData.indices->getNumElements() == 0 ) ||
          ( _vertexAttribList.size() > 0 &&
          _vertexAttribList[0].indices.valid() &&
          _vertexAttribList[0].indices->getNumElements() == 0 ) )
    {
        return;
    }

    DrawNormal         drawNormal(_normalData.array.get(),_normalData.indices.get());
    DrawColor          drawColor(_colorData.array.get(),_colorData.indices.get());
    DrawSecondaryColor drawSecondaryColor(_secondaryColorData.array.get(),_secondaryColorData.indices.get(),extensions);

    DrawFogCoord       drawFogCoord(_fogCoordData.array.get(),_fogCoordData.indices.get(),extensions);


    ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    //
    // Set up secondary color if required.
    //
    AttributeBinding secondaryColorBinding = _secondaryColorData.binding;
    if (secondaryColorBinding!=BIND_OFF && !extensions->isSecondaryColorSupported())
    {
        // switch off if not supported or have a valid data.
        secondaryColorBinding = BIND_OFF;
    }

   
    ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    //
    // Set up fog coord if required.
    //
    AttributeBinding fogCoordBinding = _fogCoordData.binding;
    if (fogCoordBinding!=BIND_OFF && !extensions->isFogCoordSupported())
    {
        // switch off if not supported or have a valid data.
        fogCoordBinding = BIND_OFF;
    }

    unsigned int normalIndex = 0;
    unsigned int colorIndex = 0;
    unsigned int secondaryColorIndex = 0;
    unsigned int fogCoordIndex = 0;

#if USE_DEFAULT_NORMAL
    // if no values are defined for normal and color provide some defaults...
    if (_normalData.binding==BIND_OFF) glNormal3f(0.0f,0.0f,1.0f);
#endif

#if USE_DEFAULT_COLOUR
    if (_colorData.binding==BIND_OFF) glColor4f(1.0f,1.0f,1.0f,1.0f);
#endif

    typedef std::vector< ref_ptr<DrawVertexAttrib> > DrawVertexAttribList;
    typedef std::map< Geometry::AttributeBinding, DrawVertexAttribList> DrawVertexAttribMap;
    DrawVertexAttribMap drawVertexAttribMap;
   
    bool vertexVertexAttributesSupported = extensions->isVertexProgramSupported();
    bool handleVertexAttributes = (!_vertexAttribList.empty() && vertexVertexAttributesSupported);

    bool usingVertexBufferObjects = _useVertexBufferObjects && state.isVertexBufferObjectSupported();
   
    if (areFastPathsUsed())
    {
   
        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //
        // fast path.       
        //
        if (usingVertexBufferObjects)     //用顶点缓冲区
        {

            //
            // Vertex Buffer Object path for defining vertex arrays.
            //
            state.setNormalPointer(_normalData.binding==BIND_PER_VERTEX ? _normalData.array.get() : 0);
            state.setColorPointer(_colorData.binding==BIND_PER_VERTEX ? _colorData.array.get() : 0);
            state.setSecondaryColorPointer(_secondaryColorData.binding==BIND_PER_VERTEX ? _secondaryColorData.array.get() : 0);
            state.setFogCoordPointer(_fogCoordData.binding==BIND_PER_VERTEX ? _fogCoordData.array.get() : 0);

            unsigned int unit;
            for(unit=0;unit<_texCoordList.size();++unit)
            {
                state.setTexCoordPointer(unit, _texCoordList[unit].array.get());
            }
            state.disableTexCoordPointersAboveAndIncluding(unit);

            if( handleVertexAttributes )
            {
                unsigned int index;
                for( index = 0; index < _vertexAttribList.size(); ++index )
                {
                    const Array* array = _vertexAttribList[index].array.get();
                    const AttributeBinding ab = _vertexAttribList[index].binding;
                    state.setVertexAttribPointer(index, (ab==BIND_PER_VERTEX ? array : 0), _vertexAttribList[index].normalize);

                    if(array && ab!=BIND_PER_VERTEX)
                    {
                        const IndexArray* indexArray = _vertexAttribList[index].indices.get();

                        if( indexArray && indexArray->getNumElements() > 0 )
                        {
                            drawVertexAttribMap[ab].push_back(
                                new DrawVertexAttrib(extensions,index,_vertexAttribList[index].normalize,array,indexArray) );
                        }
                        else
                        {
                            drawVertexAttribMap[ab].push_back(
                                new DrawVertexAttrib(extensions,index,_vertexAttribList[index].normalize,array,0) );
                        }
                    }
                }
                state.disableVertexAttribPointersAboveAndIncluding( index );
               
            }
            else if (vertexVertexAttributesSupported)
            {
                state.disableVertexAttribPointersAboveAndIncluding( 0 );
            }

            state.setVertexPointer(_vertexData.array.get());//传入顶点数组及指针


        }
        else
        {
            //std::cout << "none VertexBuffer path"<<std::endl;

            //
            // Non Vertex Buffer Object path for defining vertex arrays.
            //           
            if( _vertexData.array.valid() )
                state.setVertexPointer(_vertexData.array->getDataSize(),_vertexData.array->getDataType(),0,_vertexData.array->getDataPointer());
            else
                state.disableVertexPointer();

            if (_normalData.binding==BIND_PER_VERTEX && _normalData.array.valid())
                state.setNormalPointer(_normalData.array->getDataType(),0,_normalData.array->getDataPointer());
            else
                state.disableNormalPointer();

            if (_colorData.binding==BIND_PER_VERTEX && _colorData.array.valid())
                state.setColorPointer(_colorData.array->getDataSize(),_colorData.array->getDataType(),0,_colorData.array->getDataPointer());
            else
                state.disableColorPointer();

            if (secondaryColorBinding==BIND_PER_VERTEX && _secondaryColorData.array.valid())
                state.setSecondaryColorPointer(_secondaryColorData.array->getDataSize(),_secondaryColorData.array->getDataType(),0,_secondaryColorData.array->getDataPointer());
            else
                state.disableSecondaryColorPointer();

            if (fogCoordBinding==BIND_PER_VERTEX && _fogCoordData.array.valid())
                state.setFogCoordPointer(GL_FLOAT,0,_fogCoordData.array->getDataPointer());
            else
                state.disableFogCoordPointer();

            unsigned int unit;
            for(unit=0;unit<_texCoordList.size();++unit)
            {
                const Array* array = _texCoordList[unit].array.get();
                if (array)
                    state.setTexCoordPointer(unit,array->getDataSize(),array->getDataType(),0,array->getDataPointer());
                else
                    state.disableTexCoordPointer(unit);
            }
            state.disableTexCoordPointersAboveAndIncluding(unit);

            if( handleVertexAttributes )
            {
                unsigned int index;
                for( index = 0; index < _vertexAttribList.size(); ++index )
                {
                    const Array* array = _vertexAttribList[index].array.get();
                    const AttributeBinding ab = _vertexAttribList[index].binding;

                    if( ab == BIND_PER_VERTEX && array )
                    {
                        state.setVertexAttribPointer( index, array->getDataSize(), array->getDataType(),
                            _vertexAttribList[index].normalize, 0, array->getDataPointer() );
                    }
                    else
                    {
                        if( array )
                        {
                            const IndexArray* indexArray = _vertexAttribList[index].indices.get();

                            if( indexArray && indexArray->getNumElements() > 0 )
                            {
                                drawVertexAttribMap[ab].push_back(
                                    new DrawVertexAttrib(extensions,index,_vertexAttribList[index].normalize,array,indexArray) );
                            }
                            else
                            {
                                drawVertexAttribMap[ab].push_back(
                                    new DrawVertexAttrib(extensions,index,_vertexAttribList[index].normalize,array,0) );
                            }
                        }

                        state.disableVertexAttribPointer( index );
                    }
                }
                state.disableVertexAttribPointersAboveAndIncluding( index );
               
            }
            else if (vertexVertexAttributesSupported)
            {
                state.disableVertexAttribPointersAboveAndIncluding( 0 );
            }
        }
       
        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //
        // pass the overall binding values onto OpenGL.
        //
        if (_normalData.binding==BIND_OVERALL)      drawNormal(normalIndex++);
        if (_colorData.binding==BIND_OVERALL)       drawColor(colorIndex++);
        if (secondaryColorBinding==BIND_OVERALL)    drawSecondaryColor(secondaryColorIndex++);
        if (fogCoordBinding==BIND_OVERALL)          drawFogCoord(fogCoordIndex++);
        if (handleVertexAttributes)
        {
            DrawVertexAttribList &list = drawVertexAttribMap[BIND_OVERALL];

            for( unsigned int i = 0; i < list.size(); ++i )
            {
                list[i]->applyAndIncrement();
            }
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //
        // draw the primitives themselves.
        //
        for(PrimitiveSetList::const_iterator itr=_primitives.begin();
            itr!=_primitives.end();
            ++itr)
        {

            if (_normalData.binding==BIND_PER_PRIMITIVE_SET)      drawNormal(normalIndex++);
            if (_colorData.binding==BIND_PER_PRIMITIVE_SET)       drawColor(colorIndex++);
            if (secondaryColorBinding==BIND_PER_PRIMITIVE_SET)    drawSecondaryColor(secondaryColorIndex++);
            if (fogCoordBinding==BIND_PER_PRIMITIVE_SET)          drawFogCoord(fogCoordIndex++);
            if (handleVertexAttributes)
            {
                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE_SET];

                for( unsigned int i = 0; i < list.size(); ++i )
                {
                    list[i]->applyAndIncrement();
                }
            }

            (*itr)->draw(state, usingVertexBufferObjects);//内部生成顶点纹理索引,并绑定画图

        }

        if (usingVertexBufferObjects)
        {
#if 1
            state.unbindVertexBufferObject();
            state.unbindElementBufferObject();
#endif
        }

    }
    else
    {  

        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //
        // slow path.       
        //
       

        typedef std::vector< ref_ptr<DrawMultiTexCoord> > DrawTexCoordList;
        DrawTexCoordList drawTexCoordList;
        drawTexCoordList.reserve(_texCoordList.size());

        // fallback if multitexturing not supported.
        ref_ptr<DrawTexCoord> drawTextCoord;

        if (extensions->isMultiTexSupported() && _texCoordList.size()>1)
        {
            // multitexture supported..
            for(unsigned int unit=0;unit!=_texCoordList.size();++unit)
            {
                const ArrayData& texcoordData = _texCoordList[unit];
                if (texcoordData.array.valid() && texcoordData.array->getNumElements()>0)
                {
                    if (texcoordData.indices.valid() && texcoordData.indices->getNumElements()>0)
                    {
                        drawTexCoordList.push_back(new DrawMultiTexCoord(GL_TEXTURE0+unit,texcoordData.array.get(),texcoordData.indices.get(),
                                                                         extensions));
                    }
                    else
                    {
                        drawTexCoordList.push_back(new DrawMultiTexCoord(GL_TEXTURE0+unit,texcoordData.array.get(),0,
                                                                          extensions));
                    }
                }
            }
        }
        else
        {
            if (!_texCoordList.empty())
            {
                const ArrayData& texcoordData = _texCoordList[0];
                if (texcoordData.array.valid() && texcoordData.array->getNumElements()>0)
                {
                    if (texcoordData.indices.valid())
                    {
                        if (texcoordData.indices->getNumElements()>0)
                        {
                            drawTextCoord = new DrawTexCoord(texcoordData.array.get(),texcoordData.indices.get());
                        }
                    }
                    else
                    {
                        drawTextCoord = new DrawTexCoord(texcoordData.array.get(),0);
                    }
                }
            }
        }

        if(handleVertexAttributes)
        {
            unsigned int index;
            for( index = 1; index < _vertexAttribList.size(); ++index )
            {
                const ArrayData& vertAttribData = _vertexAttribList[index];
           
                if( vertAttribData.array.valid() && vertAttribData.array->getNumElements() > 0 )
                {
                    if( vertAttribData.indices.valid() && vertAttribData.indices->getNumElements() > 0 )
                    {
                        drawVertexAttribMap[vertAttribData.binding].push_back(
                            new DrawVertexAttrib(extensions,index,vertAttribData.normalize,vertAttribData.array.get(),vertAttribData.indices.get() ));
                    }
                    else
                    {
                        drawVertexAttribMap[vertAttribData.binding].push_back(
                            new DrawVertexAttrib(extensions,index,vertAttribData.normalize,vertAttribData.array.get(),0) );
                    }           
                }
            }
        }

        // disable all the vertex arrays in the slow path as we are
        // sending everything using glVertex etc.
        state.disableAllVertexArrays();


        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //
        // pass the overall binding values onto OpenGL.
        //
        if (_normalData.binding==BIND_OVERALL)      drawNormal(normalIndex++);
        if (_colorData.binding==BIND_OVERALL)       drawColor(colorIndex++);
        if (secondaryColorBinding==BIND_OVERALL)    drawSecondaryColor(secondaryColorIndex++);
        if (fogCoordBinding==BIND_OVERALL)          drawFogCoord(fogCoordIndex++);
        if (handleVertexAttributes)
        {
            DrawVertexAttribList &list = drawVertexAttribMap[BIND_OVERALL];

            for( unsigned int i = 0; i < list.size(); ++i )
            {
                list[i]->applyAndIncrement();
            }
        }

        // set up vertex functor.
        DrawVertex drawVertex(_vertexData.array.get(),_vertexData.indices.get());

        bool useVertexAttrib =  _vertexAttribList.size() > 0 &&
                                _vertexAttribList[0].array.valid() &&
                                 _vertexAttribList[0].indices->getNumElements();

        ref_ptr<DrawVertexAttrib> drawVertexAttribZero;
        if( useVertexAttrib )
        {
            drawVertexAttribZero = new DrawVertexAttrib(extensions,0,
                _vertexAttribList[0].normalize,_vertexAttribList[0].array.get(),
                _vertexAttribList[0].indices.get());
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
        //
        // draw the primitives themselves.
        //
        for(PrimitiveSetList::const_iterator itr=_primitives.begin();
            itr!=_primitives.end();
            ++itr)
        {
            if (_normalData.binding==BIND_PER_PRIMITIVE_SET)           drawNormal(normalIndex++);
            if (_colorData.binding==BIND_PER_PRIMITIVE_SET)            drawColor(colorIndex++);
            if (secondaryColorBinding==BIND_PER_PRIMITIVE_SET)    drawSecondaryColor(secondaryColorIndex++);
            if (fogCoordBinding==BIND_PER_PRIMITIVE_SET)          drawFogCoord(fogCoordIndex++);
            if (handleVertexAttributes)
            {
                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE_SET];

                for( unsigned int i = 0; i < list.size(); ++i )
                {
                    list[i]->applyAndIncrement();
                }
            }

            const PrimitiveSet* primitiveset = itr->get();
            GLenum mode=primitiveset->getMode();

            unsigned int primLength;
            switch(mode)
            {
                case(GL_POINTS):    primLength=1; break;
                case(GL_LINES):     primLength=2; break;
                case(GL_TRIANGLES): primLength=3; break;
                case(GL_QUADS):     primLength=4; break;
                default:            primLength=0; break; // compute later when =0.
            }


            // draw primitives by the more flexible "slow" path,
            // sending OpenGL glBegin/glVertex.../glEnd().
            switch(primitiveset->getType())                  //glBegin()及glEnd()画图
            {
                case(PrimitiveSet::DrawArraysPrimitiveType):
                {
                    if (primLength==0) primLength=primitiveset->getNumIndices();

                    const DrawArrays* drawArray = static_cast<const DrawArrays*>(primitiveset);
                    glBegin(mode);

                    unsigned int primCount=0;
                    unsigned int indexEnd = drawArray->getFirst()+drawArray->getCount();
                    for(unsigned int vindex=drawArray->getFirst();
                        vindex<indexEnd;
                        ++vindex,++primCount)
                    {

                        if ((primCount%primLength)==0)
                        {
                            if (_normalData.binding==BIND_PER_PRIMITIVE)           drawNormal(normalIndex++);
                            if (_colorData.binding==BIND_PER_PRIMITIVE)            drawColor(colorIndex++);
                            if (secondaryColorBinding==BIND_PER_PRIMITIVE)    drawSecondaryColor(secondaryColorIndex++);
                            if (fogCoordBinding==BIND_PER_PRIMITIVE)          drawFogCoord(fogCoordIndex++);
                            if (handleVertexAttributes)
                            {
                                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE];

                                for( unsigned int i = 0; i < list.size(); ++i )
                                {
                                    list[i]->applyAndIncrement();
                                }
                            }                       
                        }

                        if (_normalData.binding==BIND_PER_VERTEX)           drawNormal(vindex);
                        if (_colorData.binding==BIND_PER_VERTEX)            drawColor(vindex);
                        if (secondaryColorBinding==BIND_PER_VERTEX)    drawSecondaryColor(vindex);
                        if (fogCoordBinding==BIND_PER_VERTEX)          drawFogCoord(vindex);
                        if (handleVertexAttributes)
                        {
                            DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_VERTEX];

                            for( unsigned int i = 0; i < list.size(); ++i )
                            {
                                list[i]->applyAndIncrement();
                            }
                        } 

                        for(DrawTexCoordList::iterator texItr=drawTexCoordList.begin();
                            texItr!=drawTexCoordList.end();
                            ++texItr)
                        {
                            (*(*texItr))(vindex);
                        }
                        if (drawTextCoord.valid()) (*drawTextCoord)(vindex);

                        if( useVertexAttrib )
                        {
                            (*drawVertexAttribZero)(vindex);
                        }
                        else
                        {
                            drawVertex(vindex);
                        }
                    }
                   
                    glEnd();
                    break;
                }
                case(PrimitiveSet::DrawArrayLengthsPrimitiveType):
                {

                    const DrawArrayLengths* drawArrayLengths = static_cast<const DrawArrayLengths*>(primitiveset);
                    unsigned int vindex=drawArrayLengths->getFirst();
                    for(DrawArrayLengths::const_iterator primItr=drawArrayLengths->begin();
                        primItr!=drawArrayLengths->end();
                        ++primItr)
                    {
                        unsigned int localPrimLength;
                        if (primLength==0) localPrimLength=*primItr;
                        else localPrimLength=primLength;

                        glBegin(mode);

                        for(GLsizei primCount=0;primCount<*primItr;++primCount)
                        {
                            if ((primCount%localPrimLength)==0)
                            {
                                if (_normalData.binding==BIND_PER_PRIMITIVE)           drawNormal(normalIndex++);
                                if (_colorData.binding==BIND_PER_PRIMITIVE)            drawColor(colorIndex++);
                                if (secondaryColorBinding==BIND_PER_PRIMITIVE)    drawSecondaryColor(secondaryColorIndex++);
                                if (fogCoordBinding==BIND_PER_PRIMITIVE)          drawFogCoord(fogCoordIndex++);
                                if (handleVertexAttributes)
                                {
                                    DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE];

                                    for( unsigned int i = 0; i < list.size(); ++i )
                                    {
                                        list[i]->applyAndIncrement();
                                    }
                                } 
                            }
                           
                            if (_normalData.binding==BIND_PER_VERTEX)           drawNormal(vindex);
                            if (_colorData.binding==BIND_PER_VERTEX)            drawColor(vindex);
                            if (secondaryColorBinding==BIND_PER_VERTEX)    drawSecondaryColor(vindex);
                            if (fogCoordBinding==BIND_PER_VERTEX)          drawFogCoord(vindex);
                            if (handleVertexAttributes)
                            {
                                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_VERTEX];

                                for( unsigned int i = 0; i < list.size(); ++i )
                                {
                                    list[i]->applyAndIncrement();
                                }
                            } 
                            for(DrawTexCoordList::iterator texItr=drawTexCoordList.begin();
                                texItr!=drawTexCoordList.end();
                                ++texItr)
                            {
                                (*(*texItr))(vindex);
                            }
                            if (drawTextCoord.valid()) (*drawTextCoord)(vindex);

                            if( useVertexAttrib )
                            {
                                (*drawVertexAttribZero)(vindex);
                            }
                            else
                            {
                                drawVertex(vindex);
                            }

                            ++vindex;
                        }
                       
                        glEnd();

                    }
                    break;
                }
                case(PrimitiveSet::DrawElementsUBytePrimitiveType):
                {
                    if (primLength==0) primLength=primitiveset->getNumIndices();

                    const DrawElementsUByte* drawElements = static_cast<const DrawElementsUByte*>(primitiveset);
                    glBegin(mode);

                    unsigned int primCount=0;
                    for(DrawElementsUByte::const_iterator primItr=drawElements->begin();
                        primItr!=drawElements->end();
                        ++primCount,++primItr)
                    {

                        if ((primCount%primLength)==0)
                        {
                            if (_normalData.binding==BIND_PER_PRIMITIVE)           drawNormal(normalIndex++);
                            if (_colorData.binding==BIND_PER_PRIMITIVE)            drawColor(colorIndex++);
                            if (secondaryColorBinding==BIND_PER_PRIMITIVE)    drawSecondaryColor(secondaryColorIndex++);
                            if (fogCoordBinding==BIND_PER_PRIMITIVE)          drawFogCoord(fogCoordIndex++);
                            if (handleVertexAttributes)
                            {
                                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE];

                                for( unsigned int i = 0; i < list.size(); ++i )
                                {
                                    list[i]->applyAndIncrement();
                                }
                            } 
                        }
                       
                        unsigned int vindex=*primItr;

                        if (_normalData.binding==BIND_PER_VERTEX)           drawNormal(vindex);
                        if (_colorData.binding==BIND_PER_VERTEX)            drawColor(vindex);
                        if (secondaryColorBinding==BIND_PER_VERTEX)    drawSecondaryColor(vindex);
                        if (fogCoordBinding==BIND_PER_VERTEX)          drawFogCoord(vindex);
                        if ( extensions->isVertexProgramSupported() )
                        {
                            DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_VERTEX];

                            for( unsigned int i = 0; i < list.size(); ++i )
                            {
                                list[i]->applyAndIncrement();
                            }
                        } 

                        for(DrawTexCoordList::iterator texItr=drawTexCoordList.begin();
                            texItr!=drawTexCoordList.end();
                            ++texItr)
                        {
                            (*(*texItr))(vindex);
                        }
                        if (drawTextCoord.valid()) (*drawTextCoord)(vindex);

                        if( useVertexAttrib )
                        {
                            (*drawVertexAttribZero)(vindex);
                        }
                        else
                        {
                            drawVertex(vindex);
                        }
                    }

                    glEnd();
                    break;
                }
                case(PrimitiveSet::DrawElementsUShortPrimitiveType):
                {
                    if (primLength==0) primLength=primitiveset->getNumIndices();

                    const DrawElementsUShort* drawElements = static_cast<const DrawElementsUShort*>(primitiveset);
                    glBegin(mode);

                    unsigned int primCount=0;
                    for(DrawElementsUShort::const_iterator primItr=drawElements->begin();
                        primItr!=drawElements->end();
                        ++primCount,++primItr)
                    {

                        if ((primCount%primLength)==0)
                        {
                            if (_normalData.binding==BIND_PER_PRIMITIVE)           drawNormal(normalIndex++);
                            if (_colorData.binding==BIND_PER_PRIMITIVE)            drawColor(colorIndex++);
                            if (secondaryColorBinding==BIND_PER_PRIMITIVE)    drawSecondaryColor(secondaryColorIndex++);
                            if (fogCoordBinding==BIND_PER_PRIMITIVE)          drawFogCoord(fogCoordIndex++);
                            if (handleVertexAttributes)
                            {
                                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE];

                                for( unsigned int i = 0; i < list.size(); ++i )
                                {
                                    list[i]->applyAndIncrement();
                                }
                            } 
                        }
                       
                        unsigned int vindex=*primItr;

                        if (_normalData.binding==BIND_PER_VERTEX)           drawNormal(vindex);
                        if (_colorData.binding==BIND_PER_VERTEX)            drawColor(vindex);
                        if (secondaryColorBinding==BIND_PER_VERTEX)    drawSecondaryColor(vindex);
                        if (fogCoordBinding==BIND_PER_VERTEX)          drawFogCoord(vindex);
                        if (handleVertexAttributes)
                        {
                            DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_VERTEX];

                            for( unsigned int i = 0; i < list.size(); ++i )
                            {
                                list[i]->applyAndIncrement();
                            }
                        } 

                        for(DrawTexCoordList::iterator texItr=drawTexCoordList.begin();
                            texItr!=drawTexCoordList.end();
                            ++texItr)
                        {
                            (*(*texItr))(vindex);
                        }
                        if (drawTextCoord.valid()) (*drawTextCoord)(vindex);

                        if( useVertexAttrib )
                        {
                            (*drawVertexAttribZero)(vindex);
                        }
                        else
                        {
                            drawVertex(vindex);
                        }
                    }

                    glEnd();
                    break;
                }
                case(PrimitiveSet::DrawElementsUIntPrimitiveType):
                {
                    if (primLength==0) primLength=primitiveset->getNumIndices();

                    const DrawElementsUInt* drawElements = static_cast<const DrawElementsUInt*>(primitiveset);
                    glBegin(mode);

                    unsigned int primCount=0;
                    for(DrawElementsUInt::const_iterator primItr=drawElements->begin();
                        primItr!=drawElements->end();
                        ++primCount,++primItr)
                    {

                        if ((primCount%primLength)==0)
                        {
                            if (_normalData.binding==BIND_PER_PRIMITIVE)           drawNormal(normalIndex++);
                            if (_colorData.binding==BIND_PER_PRIMITIVE)            drawColor(colorIndex++);
                            if (secondaryColorBinding==BIND_PER_PRIMITIVE)    drawSecondaryColor(secondaryColorIndex++);
                            if (fogCoordBinding==BIND_PER_PRIMITIVE)          drawFogCoord(fogCoordIndex++);
                            if ( extensions->isVertexProgramSupported() )
                            {
                                DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_PRIMITIVE];

                                for( unsigned int i = 0; i < list.size(); ++i )
                                {
                                    list[i]->applyAndIncrement();
                                }
                            } 
                        }
                       
                        unsigned int vindex=*primItr;

                        if (_normalData.binding==BIND_PER_VERTEX)           drawNormal(vindex);
                        if (_colorData.binding==BIND_PER_VERTEX)            drawColor(vindex);
                        if (secondaryColorBinding==BIND_PER_VERTEX)    drawSecondaryColor(vindex);
                        if (fogCoordBinding==BIND_PER_VERTEX)          drawFogCoord(vindex);
                        if ( extensions->isVertexProgramSupported() )
                        {
                            DrawVertexAttribList &list = drawVertexAttribMap[BIND_PER_VERTEX];

                            for( unsigned int i = 0; i < list.size(); ++i )
                            {
                                list[i]->applyAndIncrement();
                            }
                        } 

                        for(DrawTexCoordList::iterator texItr=drawTexCoordList.begin();
                            texItr!=drawTexCoordList.end();
                            ++texItr)
                        {
                            (*(*texItr))(vindex);
                        }
                        if (drawTextCoord.valid()) (*drawTextCoord)(vindex);

                        if( useVertexAttrib )
                        {
                            (*drawVertexAttribZero)(vindex);
                        }
                        else
                        {
                            drawVertex(vindex);
                        }
                    }

                    glEnd();
                    break;
                }
                default:
                {
                    break;
                }
            }
        }
    }

}

 



你可能感兴趣的:(OpenGL)