GLSL纹理布局

看见 The OpenGL Shading Language 4.6, 5.4.2 Vector and Matrix Constructors, page 101 :

要通过指定向量或标量初始化矩阵,组件将分配给中的矩阵元素 列主订单 .

mat4(float, float, float, float,  // first column
     float, float, float, float,  // second column
     float, float, float, float,  // third column
     float, float, float, float); // fourth column

这意味着如果存储矩阵( mat4 )在二维4*N RGBA纹理的线条中,如下所示:

         0           1           2           3
mat4 m0  m0[0].xyzw  m0[1].xyzw  m0[2].xyzw  m0[3].xyzw
mat4 m1  m1[0].xyzw  m1[1].xyzw  m1[2].xyzw  m1[3].xyzw
mat4 m2  m2[0].xyzw  m2[1].xyzw  m2[2].xyzw  m2[3].xyzw
mat4 m3  .....

mat4 matArray[N]; // possibly std::vector<glm::mat4>( N );

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, 4, N, 0, GL_RGBA, GL_FLOAT, matArray);

然后可以从着色器中的纹理中读取矩阵,如下所示:

uniform sampler2D matSampler; 

void main()
{
    mat4 m0 = mat4(
        texelFetch( matSampler, ivec(0, 0), 0),
        texelFetch( matSampler, ivec(1, 0), 0),
        texelFetch( matSampler, ivec(2, 0), 0),
        texelFetch( matSampler, ivec(3, 0), 0) );

    mat4 m1 = mat4(
        texelFetch( matSampler, ivec(0, 1), 0),
        texelFetch( matSampler, ivec(1, 1), 0),
        texelFetch( matSampler, ivec(2, 1), 0),
        texelFetch( matSampler, ivec(3, 1), 0) );

   .....      
}