具有数组输入的顶点着色器 [英] Vertex shader with array inputs

问题描述

给出一个看起来像这样的顶点着色器

Given a vertex shader that looks something like

#version 400 compatibility

const int max_valence = 6;

in int valence;
in vec3 patch_data[1 + 2 * max_valence];

...

将数据映射到正确的顶点属性的正确方法是什么?我正在尝试使用VBO，但是我不知道如何传递这么大的值.glVertexAttribPointer最多采用大小为4的向量.将顶点属性放入着色器的正确方法是什么? ?

What is the the proper way to map the data to the correct vertex attribs? I'm trying to use a VBO, but I can't figure out how to pass that large of a value in. glVertexAttribPointer takes at most a vector of size 4. What's the correct way to get the vertex attributes into the shader?

推荐答案

顶点属性数组在OpenGL中是合法的.但是，数组的每个成员都占用一个 separate 属性索引.它们从您赋予patch_data的任何属性索引开始连续分配.由于您使用的是GLSL 4.00，因此还应该使用layout(location = #)明确指定属性位置.

Arrays of vertex attributes are legal in OpenGL. However, each member of the array takes up a separate attribute index. They are allocated contiguously, starting from whatever attribute index you give patch_data. Since you're using GLSL 4.00, you should also be specifying attribute locations explicitly with layout(location = #).

因此，如果您这样做:

layout(location = 1) in vec3 patch_data[1 + 2 * max_valence];

然后patch_data将覆盖从1到1 + (1 + 2 * max_valence)的半开范围内的所有属性索引.

Then patch_data will cover all attribute indices on the half-open range from 1 to 1 + (1 + 2 * max_valence).

从OpenGL来看，每个数组条目都是一个单独的属性.因此，您需要为每个单独的数组索引单独调用 glVertexAttribPointer .

Each array entry is, from the OpenGL side, a separate attribute. Therefore, you need a separate glVertexAttribPointer call for each separate array index.

因此，如果您的内存中的数组数据看起来像是紧密封装的13个vec3的数组，那么您需要执行以下操作:

So if your array data in memory looks like an array of 13 vec3's, tightly packed, then you need to do this:

for(int attrib = 0; attrib < 1 + (2 * max_valence); ++attrib)
{
  glVertexAttribPointer(attrib + 1, //Attribute index starts at 1.
    3, //Each attribute is a vec3.
    GL_FLOAT, //Change as appropriate to the data you're passing.
    GL_FALSE, //Change as appropriate to the data you're passing.
    sizeof(float) * 3 * (1 + (2 * max_valence)), //Assuming that these array attributes aren't interleaved with anything else.
    reinterpret_cast<void*>(baseOffset + (attrib * 3 * sizeof(float))) //Where baseOffset is the start of the array data in the buffer object.
  );
}

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