不同着色器中的均匀块索引 [英] Uniform block index in different shaders

问题描述

查看 uniform_buffer_object 规范，不能保证一定在多个着色器程序中以相同方式定义的统一块将具有glGetUniformBlockIndex()返回的相同索引.这意味着每次我切换着色器程序时，都必须调用glBindBufferBase()为UBO分配相关的索引.

Looking at uniform_buffer_object specs, there is no guarantee that a certain uniform block that is defined the same way in multiple shader programs will have the same index returned by glGetUniformBlockIndex(). That means I have to call glBindBufferBase() to assign the UBO the relevant index every time I switch the shader program.

但是，从某些测试来看，即使统一块以不同的顺序声明，看起来统一块确实在不同的着色器程序中具有相同的索引. 看一下这两个顶点着色器:一个，

However, from some testing, it seems like a uniform block does have the same index in different shader programs, even when the uniform blocks are declared in different orders. Have a look at these two vertex shaders: one, two. (note I used the values of v1, v2.. etc to avoid inactive uniform elimination)

当查询这样的索引时:

std::cout << glGetUniformBlockIndex(prog1, "var1") << "\n";
std::cout << glGetUniformBlockIndex(prog2, "var1") << "\n";

我得到相同的索引值.查询"var2"，"var3"等时，我得到相同的结果.

I get the same index value. I get the same results when querying "var2", "var3" and so on.

这是故意的吗?为什么会发生?我可以依靠这种情况一直发生吗?

Is this intended? Why does it happen? Can I rely on this always happening?

推荐答案

获得索引后，应设置绑定点:

After you get the index you should set the binding point:

glUniformBlockBinding(prog1, glGetUniformBlockIndex(prog1, "var1"), 1);
glUniformBlockBinding(prog2, glGetUniformBlockIndex(prog2, "var1"), 1);

现在1是每个程序中var1的绑定点.

Now 1 is the binding point of var1 in each program.

您还可以在glsl中显式设置绑定:

You can also set the binding in glsl explicitly:

layout(binding = 3) uniform MatrixBlock
{
  mat4 projection;
  mat4 modelview;
};

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