OpenGLES—法线贴图

{
	1:法线介绍
	2:实例
	3:推荐博客
}

{1:法线介绍
	光的强度=光照+法线+法线贴图
	模型凹凸纹理效果=基础贴图 X 光的强度 

	模型有两种贴图
		基础贴图  例如一个盒子，盒子是木头纹理，或铁皮纹理
		法线贴图  把基础贴图中凹凸的地方生成一个张原纹理大小的贴图

	法线
	幅法线
	切线
}

{2:实例
	{
		1:Shader
		2:调用
	}

	{1:Shader
		const char* vs  = {
			"attribute vec3  inVertex;"
			"attribute vec3  inNormal;"//法线
			"attribute vec2  inTexCoord;"
			"attribute vec3  inTangent;"//切线

			"uniform mat4  MVPMatrix;"
			"uniform vec3  LightPosModel;" //光照

			"varying  vec3  LightVec;"//光的夹角
			"varying  vec2  TexCoord;"
			"void main(){"
				"gl_Position = MVPMatrix * vec4(inVertex,1);"

				//计算光的方向，在模型空间中
				//在模型空间得到的光的方向  --〉 要从模型空间转换到切线空间         
				"highp vec3 lightDirection = normalize(LightPosModel - vec3(inVertex));"

				//! 将灯的方向从模型空间，转化到tangent空间
				"highp vec3 bitangent = cross(inNormal, inTangent);"// vec3 cross(vec3 x, vec3 y) 向量x,y之间的叉积
				"highp mat3 tangentSpaceXform = mat3(inTangent, bitangent, inNormal);"//算出-〉切线坐标系
				"LightVec = lightDirection * tangentSpaceXform;"

				"TexCoord = inTexCoord;"
			"}"
		};

		const char * fs  =  {
			"precision lowp float; "
			"uniform sampler2D  sBaseTex;"
			"uniform sampler2D  sNormalMap;"//法线图

			"varying lowp    vec3  LightVec;"//光的向量
			"varying mediump vec2  TexCoord;"

			"void main(){"
				// 将像素值映射到 [-1, 1]  法线的范围是[-1，1]，rgb范围[0.1]，（[0,1]*2-1=[0-1,2-1]=[-1,1]）
				"vec3 normal = texture2D(sNormalMap, TexCoord).rgb * 2.0 - 1.0;"
				"float lightIntensity = dot(LightVec, normal);"//光的强度(算出物体上的一点光的强度)

				"vec3 texColor = texture2D(sBaseTex, TexCoord).rgb;	"
				"gl_FragColor = vec4(texColor * lightIntensity, 1.0);"
			"}"
		};
        	pValue=creteShaderProgram(vs,fs);

		inVertex    =glGetAttribLocation(pValue.pID, "inVertex");
		inNormal    =glGetAttribLocation(pValue.pID, "inNormal");
		inTexCoord  =glGetAttribLocation(pValue.pID, "inTexCoord");
		inTangent   =glGetAttribLocation(pValue.pID,"inTangent");

		MVPMatrix       =glGetUniformLocation(pValue.pID,"MVPMatrix");
		LightPosModel   =glGetUniformLocation(pValue.pID,"LightPosModel");
		sBaseTex        =glGetUniformLocation(pValue.pID,"sBaseTex");
		sNormalMap      =glGetUniformLocation(pValue.pID,"sNormalMap");
	}

	{2:调用
		bmShader.shaderBegin();
		{
			glActiveTexture(GL_TEXTURE0);
			glBindTexture(GL_TEXTURE_2D,textureBaseId);
			
			glActiveTexture(GL_TEXTURE1);
			glBindTexture(GL_TEXTURE_2D,textureNormalId);


			glUniform1i(bmShader.sBaseTex,0);
			glUniform1i(bmShader.sNormalMap,1);

			//printf("%d - %d = %d\n",GL_TEXTURE1,GL_TEXTURE0,GL_TEXTURE1-GL_TEXTURE0);

	
			static  float   angle = 0; // angle   +=  1.0f;

			CELL::matrix4 matRot(1);
			matRot.rotateY(angle);
			CELL::matrix4 matTrans;
			matTrans.translate(0,5,0);
			CELL::matrix4 matScale(1);
			matScale.scale(0.3f,0.3f,0.3f);

			CELL::matrix4 matModel    =   matTrans * matRot * matScale;

			//光源位置
			CELL::float4  vMsLightPos = CELL::float4(50, 20, 40, 1);
			vMsLightPos =   vMsLightPos * matModel;
			//CELL::matrix4 MVP =   camera._matProj * camera._matView * matModel ;
			MVP =   matProj * matView *matModel;

			glUniformMatrix4fv(bmShader.MVPMatrix,1,false,MVP.data());
			glUniform3fv(bmShader.LightPosModel,1,&vMsLightPos.x);


			VertexBumpMap*  vert    =   &model.arVertexs.front();
			glVertexAttribPointer(bmShader.inVertex,   3,  GL_FLOAT,   GL_FALSE, sizeof(VertexBumpMap), vert);
			glVertexAttribPointer(bmShader.inNormal,   3,  GL_FLOAT,   GL_FALSE, sizeof(VertexBumpMap), &vert[0].normal);
			glVertexAttribPointer(bmShader.inTexCoord, 2,  GL_FLOAT,   GL_FALSE, sizeof(VertexBumpMap), &vert[0].uv);
			glVertexAttribPointer(bmShader.inTangent,  3,  GL_FLOAT,   GL_FALSE, sizeof(VertexBumpMap), &vert[0].tangent);

			glDrawElements(GL_TRIANGLES,model.arFaces.size() * 3,GL_UNSIGNED_SHORT,&model.arFaces.front());

		}
		bmShader.shaderEnd();
	}

}

效果图

生成法线贴图工具(photoshop支持Win32/64)

支持版本 Adobe Photoshop 5.0, 5.1, 6.0, 7.0, CS, CS2, CS3, CS4, CS5 and CS6

下载地址
https://developer.nvidia.com/gameworksdownload#?dn=texture-tools-for-adobe-photoshop-8-55

源码地址  http://pan.baidu.com/s/1geVargZ  法线贴图.zip

{3:推荐博客
	http://blog.csdn.net/zp373860147/article/details/6758828	
	http://www.cnblogs.com/flytrace/p/3387748.html
}