【OpenGL】蓝宝书第三章——基础渲染

目录

正投影

透视投影

属性

Uniform值

GLTools的GLShaderManager所有内置着色器

点、线、多边形

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正投影

GLFrustum::SetOrthographic(GLfloat xMin, GLfloat xMax, GLfloat yMin, GLfloat yMax, GLfloat zMin, GLfloat zMax);

透视投影

GLFrustum::SetPerspective(float fFov, float fAspect, float fNear, float fFar); 

属性

对应UnityShader的顶点着色器输入结构体的数据，例如   VERTEX   COLOR  NORMAL   TEXTURE0 TEXTURE1  对应上 OPGL的 GLT_ATTRIBUTE_VERTEX GLT_ATTRIBUTE_COLOR GLT_ATTRIBUTE_NORMAL GLT_ATTRIBUTE_TEXTURE0  GLT_ATTRIBUTE_TEXTURE1 

它是针对每一个顶点而言的，即每一个顶点都携带有一个属性，不同顶点的属性是不一样的个体。

Uniform值

目前学习到的使用API   GLShaderManager::UseStockShader(GLenum shader, ...); 时传递给 ... 的就是Uniform值，它是针对整个批次而言的，即每一个顶点都共享一个Uniform值，这是和属性的不同之处。

GLTools的GLShaderManager所有内置着色器

单位着色器  :    GLShaderManager::UseStockShader(GLT_SHADER_IDENTITY, GLfloat vColor[4]);  
传递Uniform：vColor颜色，着色器会使用这个颜色进行绘制，并在[-1.0,1.0]坐标系绘制，只使用GLT_ATTRIBUTE_VERTEX。

平面着色器：   GLShaderManager::UseStockShader(GLT_SHADER_FLAT, GLfloat mvp[16], GLfloat vColor[4]);
传递Uniform: mvp模型视图投影矩阵和vColor颜色，着色器会使用该矩阵对顶点变换和颜色绘制，只使用GLT_ATTRIBUTE_VERTEX。

上色着色器： GLShaderManager::UseStockShader(GLT_SHADER_SHADED, GLfloat mvp[16]);
传递Uniform: mvp模型视图投影矩阵，着色器会使用该矩阵对顶点变换，会使用GLT_ATTRIBUTE_VERTEX和GLT_ATTRIBUTE_COLOR。多了一个顶点颜色属性进行上色。

默认光源着色器： GLShaderManager::UseStockShader(GLT_SHADER_DEFAULT_LIGHT, GLfloat mv[16], GLfloat p[16], GLfloat vColor[4]);
传递Uniform: mv模型视图矩阵、p投影矩阵和vColor颜色，着色器会使用这些参数进行正确的阴影、光照渲染和上色，会使用GLT_ATTRIBUTE_VERTEX和GLT_ATTRIBUTE_NORMAL。

点光源着色器： GLShaderManager::UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, GLfloat mv[16], GLfloat p[16], GLfloat vLightPos[3], GLfloat vColor[4]);
传递Uniform: mv模型视图矩阵、p投影矩阵、视图点光源位置和颜色，着色器会使用这些参数进行阴影、光照、上色，会使用GLT_ATTRIBUTE_VERTEX和GLT_ATTRIBUTE_NORMAL。

纹理替换矩阵：GLShaderManager::UseStockShader(GLT_SHADER_TEXTURE_REPLACE, GLfloat mvpMatrix[16], GLint nTextureUnit);
书上解释的不太清楚，目前姑且认为是一种替换纹理的着色器，替换的是nTextureUnit参数(Int)索引指定的纹理所应用到的顶点进行mvpMatrix矩阵的变换。

纹理调整着色器：GLShaderManager::UseStockShader(GLT_SHADER_TEXTURE_MODULATE, GLfloat mvpMatrix[16], GLfloat vColor, GLint nTextureUnit);
书上写的vColor居然不是vColor[4]，待确认内容...  大体意思是用vColor乘以一个nTextureUnit指定的纹理颜色? mvpMatrix[16]不知道干嘛的，会使用GLT_ATTRIBUTE_VERTEX和GLT_ATTRIBUTE_TEXTURE0。

纹理光源着色器：GLShaderManager::UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF, GLfloat mvMatrix, GLfloat pMatrix[16], GLfloat vLightPos[3], GLfloat vBaseColor[4], GLint nTextureUnit);
书上写的mvMatrix进入不是mvMatrix[16]，将一个纹理通过漫反射照明计算进行调整（乘以vColor?)，光线用的是点光源位置，会使用GLT_ATTRIBUTE_VERTEX、GLT_ATTRIBUTE_NORMAL和GLT_ATTRIBUTE_TTEXTURE0。

以上内容暂时记录更详细的理解后面会经常用会到时理解清楚。

点、线、多边形

GL_Point 点             glPointSize(GLfloat size)函数定义点的大小，glGetFloatv(GL_POINT_SIZE_RANGE,  sizes) 获取支持的点大小范围  glGetFloatv(GL_POINT_SIZE_GRANULARITY, &step)获取支持的点大小增量。
GL_LINES 每一对点形成的线段  glEnable(GL_PROMGRAM_POINT_SIZE)启用点大小模式 在程序中着色器代码里用gl_PointSize=5.0 设置点大小,案例设置的是4.0
GL_LINE_STRIP 从第一个顶点依次经过每个顶点绘制成的线条  glLineWidth(GLfloat width); 设置线宽度  
GL_LINE_LOOP 和GL_LINE_STRIP相同，但最后一个顶点和第一个顶点也连起来了   
GL_TRIANGLES 每3个顶点定义一个新的三角形   
GL_TRIANGLE_STRIP 共用一个三角形边顶点(strip条带)上的顶点的一组三角形（即会出现共用顶点的三角形，在GL_TRIANGLE基础上把空隙连上了和GL_LINE_STRIP一样意思)，绘制一串相连的三角形
GL_TRIANGLE_FAN 以一个圆点为中心呈扇形排列，共用相邻顶点的一组三角形。（即第一个v0顶点和其他2个v1和v2顶点构成第一个三角形后 之后每一次增加的顶点都会与v0和相邻顶点构成一个新的三角形，具体看示例图）

// Primitieves.cpp
// OpenGL SuperBible, Chapter 2
// Demonstrates the 7 Geometric Primitives
// Program by Richard S. Wright Jr.

#pragma comment(lib, "gltools.lib")
#include 	// OpenGL toolkit
#include 
#include 
#include 
#include 
#include 

#include 
#ifdef __APPLE__
#include 
#else
#define FREEGLUT_STATIC
#include 
#endif

// An assortment of needed classes
GLShaderManager		shaderManager;
GLMatrixStack		modelViewMatrix;
GLMatrixStack		projectionMatrix;
GLFrame				cameraFrame;
GLFrame             objectFrame;
GLFrustum			viewFrustum;

GLBatch				pointBatch;
GLBatch				lineBatch;
GLBatch				lineStripBatch;
GLBatch				lineLoopBatch;
GLBatch				triangleBatch;
GLBatch             triangleStripBatch;
GLBatch             triangleFanBatch;

GLGeometryTransform	transformPipeline;
M3DMatrix44f		shadowMatrix;


GLfloat vGreen[] = { 0.0f, 1.0f, 0.0f, 1.0f };
GLfloat vBlack[] = { 0.0f, 0.0f, 0.0f, 1.0f };


// Keep track of effects step
int nStep = 0;


// This function does any needed initialization on the rendering context. 
// This is the first opportunity to do any OpenGL related tasks.
void SetupRC()
{
	// Black background
	glClearColor(0.7f, 0.7f, 0.7f, 1.0f);

	shaderManager.InitializeStockShaders();

	glEnable(GL_DEPTH_TEST);

	transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);

	cameraFrame.MoveForward(-15.0f);

	//
	// Some points, more or less in the shape of Florida
	GLfloat vCoast[24][3] = { {2.80, 1.20, 0.0 }, {2.0,  1.20, 0.0 },
							{2.0,  1.08, 0.0 },  {2.0,  1.08, 0.0 },
							{0.0,  0.80, 0.0 },  {-.32, 0.40, 0.0 },
							{-.48, 0.2, 0.0 },   {-.40, 0.0, 0.0 },
							{-.60, -.40, 0.0 },  {-.80, -.80, 0.0 },
							{-.80, -1.4, 0.0 },  {-.40, -1.60, 0.0 },
							{0.0, -1.20, 0.0 },  { .2, -.80, 0.0 },
							{.48, -.40, 0.0 },   {.52, -.20, 0.0 },
							{.48,  .20, 0.0 },   {.80,  .40, 0.0 },
							{1.20, .80, 0.0 },   {1.60, .60, 0.0 },
							{2.0, .60, 0.0 },    {2.2, .80, 0.0 },
							{2.40, 1.0, 0.0 },   {2.80, 1.0, 0.0 } };

	// Load point batch
	pointBatch.Begin(GL_POINTS, 24);
	pointBatch.CopyVertexData3f(vCoast);
	pointBatch.End();

	// Load as a bunch of line segments
	lineBatch.Begin(GL_LINES, 24);
	lineBatch.CopyVertexData3f(vCoast);
	lineBatch.End();

	// Load as a single line segment
	lineStripBatch.Begin(GL_LINE_STRIP, 24);
	lineStripBatch.CopyVertexData3f(vCoast);
	lineStripBatch.End();

	// Single line, connect first and last points
	lineLoopBatch.Begin(GL_LINE_LOOP, 24);
	lineLoopBatch.CopyVertexData3f(vCoast);
	lineLoopBatch.End();

	// For Triangles, we'll make a Pyramid
	GLfloat vPyramid[12][3] = { -2.0f, 0.0f, -2.0f,
								2.0f, 0.0f, -2.0f,
								0.0f, 4.0f, 0.0f,

								2.0f, 0.0f, -2.0f,
								2.0f, 0.0f, 2.0f,
								0.0f, 4.0f, 0.0f,

								2.0f, 0.0f, 2.0f,
								-2.0f, 0.0f, 2.0f,
								0.0f, 4.0f, 0.0f,

								-2.0f, 0.0f, 2.0f,
								-2.0f, 0.0f, -2.0f,
								 0.0f, 4.0f, 0.0f };

	triangleBatch.Begin(GL_TRIANGLES, 12);
	triangleBatch.CopyVertexData3f(vPyramid);
	triangleBatch.End();


	// For a Triangle fan, just a 6 sided hex. Raise the center up a bit
	GLfloat vPoints[100][3];    // Scratch array, more than we need
	int nVerts = 0;
	GLfloat r = 3.0f;
	vPoints[nVerts][0] = 0.0f;
	vPoints[nVerts][1] = 0.0f;
	vPoints[nVerts][2] = 0.0f;

	for (GLfloat angle = 0; angle < M3D_2PI; angle += M3D_2PI / 6.0f) {
		nVerts++;
		vPoints[nVerts][0] = float(cos(angle)) * r;
		vPoints[nVerts][1] = float(sin(angle)) * r;
		vPoints[nVerts][2] = -0.5f;
	}

	// Close the fan
	nVerts++;
	vPoints[nVerts][0] = r;
	vPoints[nVerts][1] = 0;
	vPoints[nVerts][2] = 0.0f;

	// Load it up
	triangleFanBatch.Begin(GL_TRIANGLE_FAN, 8);
	triangleFanBatch.CopyVertexData3f(vPoints);
	triangleFanBatch.End();

	// For triangle strips, a little ring or cylinder segment
	int iCounter = 0;
	GLfloat radius = 3.0f;
	for (GLfloat angle = 0.0f; angle <= (2.0f*M3D_PI); angle += 0.3f)
	{
		GLfloat x = radius * sin(angle);
		GLfloat y = radius * cos(angle);

		// Specify the point and move the Z value up a little	
		vPoints[iCounter][0] = x;
		vPoints[iCounter][1] = y;
		vPoints[iCounter][2] = -0.5;
		iCounter++;

		vPoints[iCounter][0] = x;
		vPoints[iCounter][1] = y;
		vPoints[iCounter][2] = 0.5;
		iCounter++;
	}

	// Close up the loop
	vPoints[iCounter][0] = vPoints[0][0];
	vPoints[iCounter][1] = vPoints[0][1];
	vPoints[iCounter][2] = -0.5;
	iCounter++;

	vPoints[iCounter][0] = vPoints[1][0];
	vPoints[iCounter][1] = vPoints[1][1];
	vPoints[iCounter][2] = 0.5;
	iCounter++;

	// Load the triangle strip
	triangleStripBatch.Begin(GL_TRIANGLE_STRIP, iCounter);
	triangleStripBatch.CopyVertexData3f(vPoints);
	triangleStripBatch.End();
}


void DrawWireFramedBatch(GLBatch* pBatch)
{
	// Draw the batch solid green
	shaderManager.UseStockShader(GLT_SHADER_FLAT, transformPipeline.GetModelViewProjectionMatrix(), vGreen);
	pBatch->Draw();

	// Draw black outline
	glPolygonOffset(-1.0f, -1.0f);      // Shift depth values
	glEnable(GL_POLYGON_OFFSET_LINE);

	// Draw lines antialiased
	glEnable(GL_LINE_SMOOTH);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	// Draw black wireframe version of geometry
	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
	glLineWidth(2.5f);
	shaderManager.UseStockShader(GLT_SHADER_FLAT, transformPipeline.GetModelViewProjectionMatrix(), vBlack);
	pBatch->Draw();

	// Put everything back the way we found it
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
	glDisable(GL_POLYGON_OFFSET_LINE);
	glLineWidth(1.0f);
	glDisable(GL_BLEND);
	glDisable(GL_LINE_SMOOTH);
}

// Called to draw scene
void RenderScene(void)
{
	// Clear the window with current clearing color
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

	modelViewMatrix.PushMatrix();
	M3DMatrix44f mCamera;
	cameraFrame.GetCameraMatrix(mCamera);
	modelViewMatrix.MultMatrix(mCamera);

	M3DMatrix44f mObjectFrame;
	objectFrame.GetMatrix(mObjectFrame);
	modelViewMatrix.MultMatrix(mObjectFrame);

	shaderManager.UseStockShader(GLT_SHADER_FLAT, transformPipeline.GetModelViewProjectionMatrix(), vBlack);

	switch (nStep) {
	case 0:
		glPointSize(4.0f);
		pointBatch.Draw();
		glPointSize(1.0f);
		break;
	case 1:
		glLineWidth(2.0f);
		lineBatch.Draw();
		glLineWidth(1.0f);
		break;
	case 2:
		glLineWidth(2.0f);
		lineStripBatch.Draw();
		glLineWidth(1.0f);
		break;
	case 3:
		glLineWidth(2.0f);
		lineLoopBatch.Draw();
		glLineWidth(1.0f);
		break;
	case 4:
		DrawWireFramedBatch(&triangleBatch);
		break;
	case 5:
		DrawWireFramedBatch(&triangleStripBatch);
		break;
	case 6:
		DrawWireFramedBatch(&triangleFanBatch);
		break;
	}

	modelViewMatrix.PopMatrix();

	// Flush drawing commands
	glutSwapBuffers();
}


// Respond to arrow keys by moving the camera frame of reference
void SpecialKeys(int key, int x, int y)
{
	if (key == GLUT_KEY_UP)
		objectFrame.RotateWorld(m3dDegToRad(-5.0f), 1.0f, 0.0f, 0.0f);

	if (key == GLUT_KEY_DOWN)
		objectFrame.RotateWorld(m3dDegToRad(5.0f), 1.0f, 0.0f, 0.0f);

	if (key == GLUT_KEY_LEFT)
		objectFrame.RotateWorld(m3dDegToRad(-5.0f), 0.0f, 1.0f, 0.0f);

	if (key == GLUT_KEY_RIGHT)
		objectFrame.RotateWorld(m3dDegToRad(5.0f), 0.0f, 1.0f, 0.0f);

	glutPostRedisplay();
}




// A normal ASCII key has been pressed.
// In this case, advance the scene when the space bar is pressed
void KeyPressFunc(unsigned char key, int x, int y)
{
	if (key == 32)
	{
		nStep++;

		if (nStep > 6)
			nStep = 0;
	}

	switch (nStep)
	{
	case 0:
		glutSetWindowTitle("GL_POINTS");
		break;
	case 1:
		glutSetWindowTitle("GL_LINES");
		break;
	case 2:
		glutSetWindowTitle("GL_LINE_STRIP");
		break;
	case 3:
		glutSetWindowTitle("GL_LINE_LOOP");
		break;
	case 4:
		glutSetWindowTitle("GL_TRIANGLES");
		break;
	case 5:
		glutSetWindowTitle("GL_TRIANGLE_STRIP");
		break;
	case 6:
		glutSetWindowTitle("GL_TRIANGLE_FAN");
		break;
	}

	glutPostRedisplay();
}

// Window has changed size, or has just been created. In either case, we need
// to use the window dimensions to set the viewport and the projection matrix.
void ChangeSize(int w, int h)
{
	glViewport(0, 0, w, h);
	viewFrustum.SetPerspective(35.0f, float(w) / float(h), 1.0f, 500.0f);
	projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
	modelViewMatrix.LoadIdentity();
}

// Main entry point for GLUT based programs
int main(int argc, char* argv[])
{
	gltSetWorkingDirectory(argv[0]);

	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);
	glutInitWindowSize(800, 600);
	glutCreateWindow("GL_POINTS");
	glutReshapeFunc(ChangeSize);
	glutKeyboardFunc(KeyPressFunc);
	glutSpecialFunc(SpecialKeys);
	glutDisplayFunc(RenderScene);

	GLenum err = glewInit();
	if (GLEW_OK != err) {
		fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
		return 1;
	}


	SetupRC();

	glutMainLoop();
	return 0;
}

注意 #pragma comment(lib, "gltools.lib") 只是我个人项目所需，如果有报错可注释掉.