我正在尝试在我的OpenGL程序中实现Instancing。我已经让它工作了，然后决定通过将Model-View-Projection乘法矩阵作为输入发送到GLSL程序中来使我的GLSL代码更加高效，这样CPU会为每个实例计算它，而不是GPU。这是我的顶点着色器代码（大部分与我的问题无关）：
#version 330 core
// Input vertex data, different for all executions of this shader.
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 2) in vec3 vertexColor;
layout(location = 3) in vec3 vertexNormal_modelspace;
layout(location = 6) in mat4 models;
layout(location = 10) in mat4 modelsV;
layout(location = 14) in mat4 modelsVP;
// Output data ; will be interpolated for each fragment.
out vec3 newColor;
out vec3 Position_worldspace;
out vec3 Normal_cameraspace;
out vec3 EyeDirection_cameraspace;
// Values that stay constant for the whole mesh.
uniform mat4 MVP;
uniform mat4 MV;
uniform mat4 P;
uniform mat4 V;
uniform mat4 M;
uniform int num_lights;
uniform vec3 Lights[256];
void main(){
// Output position of the vertex, in clip space : MVP * position
gl_Position = P * modelsV * vec4(vertexPosition_modelspace,1);
// Position of the vertex, in worldspace : M * position
Position_worldspace = (models * vec4(vertexPosition_modelspace,1)).xyz;
// Vector that goes from the vertex to the camera, in camera space.
// In camera space, the camera is at the origin (0,0,0).
vec3 vertexPosition_cameraspace = ( modelsV * vec4(vertexPosition_modelspace,1)).xyz;
EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace;
// Normal of the the vertex, in camera space
Normal_cameraspace = ( modelsV * vec4(vertexNormal_modelspace,0)).xyz;
// UV of the vertex. No special space for this one.
newColor = vertexColor;
}
上述代码有效，但仅因为我没有使用最后一个输入的modelsVP计算gl_position。如果我使用它（而不是计算P * modelsV），实例将无法绘制，并且会出现以下错误：
Linking program
Compiling shader : GLSL/meshColor.vertexshader
Compiling shader : GLSL/meshColor.fragmentshader
Linking program
Vertex info
0(10) : error C5102: input semantic attribute "ATTR" has too big of a numeric index (16)
0(10) : error C5102: input semantic attribute "ATTR" has too big of a numeric index (16)
0(10) : error C5041: cannot locate suitable resource to bind variable "modelsVP". Possibly large array.
我确定我在我的OpenGL代码中正确地链接了它，因为如果我将输入位置modelsVP与modelsV交换，使其变为10而不是14，我就能够使用它，但不能使用modelsV。你的顶点着色器中的输入数量是否有最大限制？我真的想不出还有其他原因会导致这个错误...
我将包括更多相关的OpenGL代码，但我相当确定它是正确的（它不都在同一个类或方法中）：
// Buffer data for VBO. The numbers must match the layout in the GLSL code.
#define position 0
#define uv 1
#define color 2
#define normal 3
#define tangent 4
#define bitangent 5
#define model 6 // 4x4 matrices take 4 positions
#define modelV 10
#define modelVP 14
#define num_buffers 18
GLuint VBO[num_buffers];
glGenBuffers(num_buffers, VBO);
for( int i=0; i<ModelMatrices.size(); i++ )
{
mvp.push_back( projection * view * ModelMatrices.at(i) );
mv.push_back( view * ModelMatrices.at(i) );
}
glBindBuffer(GL_ARRAY_BUFFER, VBO[model]);
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::mat4) * ModelMatrices.size(), &ModelMatrices[0], GL_DYNAMIC_DRAW);
for (unsigned int i = 0; i < 4 ; i++) {
glEnableVertexAttribArray(model + i);
glVertexAttribPointer(model + i, 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4),
(const GLvoid*)(sizeof(GLfloat) * i * 4));
glVertexAttribDivisor(model + i, 1);
}
glBindBuffer(GL_ARRAY_BUFFER, VBO[modelV]);
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::mat4) * mv.size(), &mv[0], GL_DYNAMIC_DRAW);
for (unsigned int i = 0; i < 4 ; i++) {
glEnableVertexAttribArray(modelV + i);
glVertexAttribPointer(modelV + i, 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4),
(const GLvoid*)(sizeof(GLfloat) * i * 4));
glVertexAttribDivisor(modelV + i, 1);
}
glBindBuffer(GL_ARRAY_BUFFER, VBO[modelVP]);
glBufferData(GL_ARRAY_BUFFER, sizeof(glm::mat4) * mvp.size(), &mvp[0], GL_DYNAMIC_DRAW);
for (unsigned int i = 0; i < 4 ; i++) {
glEnableVertexAttribArray(modelVP + i);
glVertexAttribPointer(modelVP + i, 4, GL_FLOAT, GL_FALSE, sizeof(glm::mat4), (const GLvoid*)(sizeof(GLfloat) * i * 4));
glVertexAttribDivisor(modelVP + i, 1);
}
models是模型矩阵（顺带一提：GLSL没有标识符大小限制。为这些使用更好的名称）。您不应该在世界空间中进行任何计算。在世界空间中可以进行的任何操作都可以在相机空间或位置上与相机定向对齐的空间中进行。因此，您不需要models。而且您也不需要modelsVP，因为您必须在任何情况下计算vertexPosition_cameraspace。所以您最好只需使用P将其转换为gl_Position。 - Nicol Bolas{ vec3 position; quat4 tangent; vec3 texcoord; vec4 color; vec3 modelPosition; quat4 modelOrientation; }中，这适用于6个属性位置。 - Yakov Galka