GLSL Instancing - 顶点数据的最大输入数? [英] GLSL Instancing - Max number of inputs for vertex data?

问题描述

我正在尝试在我的 OpenGL 程序中实现实例化.我让它工作，然后决定通过将模型-视图-投影乘法矩阵作为输入发送到 GLSL 程序来使我的 GLSL 代码更高效，以便 CPU 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):

I am trying to implement instancing in my OpenGL program. I got it to work, and then decided to make my GLSL code more efficient by sending the Model-View-Projection multiplication matrix as input to the GLSL program, so that the CPU computes it for each instance, opposed to the GPU. Here is my vertex shader code (most of it is irrelevant to my question):

#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;

}

上面的代码有效，但只是因为我没有使用最后一个输入模型VP来计算gl_position.如果我确实使用它(而不是计算 P*modelsV)，则不会绘制实例，并且出现此错误:

The above code works, but only because I'm not using the last input modelsVP to calculate gl_position. If I do use it (instead of computing P*modelsV), the instances won't be drawn, and I get this error:

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 代码中正确链接了它，因为如果我将输入位置 modelsVP 与 modelsV 交换使其为 10 而不是 14，我可以使用它，但不能使用 modelsV.您的顶点着色器是否有最大数量的输入?我真的想不出任何其他想法为什么我会得到这个错误......

I'm sure I'm linking it correctly in my OpenGL code, because if I swap the input location modelsVP with modelsV so that it is 10 instead of 14, I am able to use it, but not modelsV. Is there a maximum number of inputs you can have for your vertex shader? I really can't think of any other idea of why else I would get this error...

我将在此处包含更多相关的 OpenGL 代码，但我很确定它是正确的(并非全部在同一个类或方法中):

I'll include more of my OpenGL code that is relevant here, but I'm pretty sure that it's correct (it's not all in the same class or method):

// 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);
}

推荐答案

OpenGL 要求实现提供至少 16 个 4 分量顶点属性.因此，不能保证所有实现都支持索引 16；有关详细信息，请参阅 GL_MAX_VERTEX_ATTRIBS.

OpenGL mandates implementations offer a minimum of 16 4-component vertex attributes. Therefore an index of 16 is not guaranteed to be supported by all implementations; see GL_MAX_VERTEX_ATTRIBS for more details.

您的 mat4 顶点属性计为 4 个 4 分量属性，因此在仅支持 16 个 4 分量顶点属性的实现中，索引 14 超出范围.

Your mat4 vertex attributes count as 4 4-component attributes, so an index of 14 is out of range on implementations that only support 16 4-component vertex attributes.

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