ATI 显卡上 GLSL 着色器的顶点统一组件的实际数量是多少？

发布于 2024-12-22 17:45:53 字数 1163 浏览 1 评论 0原文

我正在为配备 AMD Radeon HD 6970M 2048 MB 显卡的 iMac 编写 GLSL 顶点着色器：

GL_MAX_VERTEX_ATTRIBS: 16
GL_MAX_VERTEX_UNIFORM_COMPONENTS: 4096
GL_VERSION: 2.1 ATI-7.12.9
GL_SHADING_LANGUAGE_VERSION: 1.20

在我的着色器中，我希望拥有大量统一的 mat4：

uniform mat4 T[65]

但如果我尝试拥有其中 65 个着色器（秘密地））切换到 Apple 软件渲染器模式。如果我改用 64：

uniform mat4 T[64]

一切都很好。

似乎是超过制服最大数量的问题。但正如我上面所写，我得到 GL_MAX_VERTEX_UNIFORM_COMPONENTS 的 4096，因此 4096/(4*4) = 256 而不是 64...

OpenGL.org wiki 说

ATI/AMD 注意：ATI 最大组件值是错误的。它们是组件的实际数量除以 4。

但是读到这里我会想，如果我查询 GL_MAX_VERTEX_UNIFORM_COMPONENTS 并得到 4096，我实际上有 16,384 个。情况似乎是 GL_MAX_VERTEX_UNIFORM_COMPONENTS 返回组件的实际数量乘以 4。这将得到 1024/(4*4) = 64。

有人能证实这一点吗？

编辑： 我的着色器很简单：

#version 120

// 65 goes into software render mode
#define MAX_T 64
attribute vec4 indices;
uniform mat4 T[MAX_T];

void main()
{
  gl_Position =  T[int(indices[0])]*gl_Vertex;
}

原文

I'm writing a GLSL vertex shader for an iMac with a AMD Radeon HD 6970M 2048 MB graphics card:

GL_MAX_VERTEX_ATTRIBS: 16
GL_MAX_VERTEX_UNIFORM_COMPONENTS: 4096
GL_VERSION: 2.1 ATI-7.12.9
GL_SHADING_LANGUAGE_VERSION: 1.20

In my shader I would like to have a large array of uniform mat4s:

uniform mat4 T[65]

but if I try to have 65 of these my shader (secretly) switches to Apple Software Renderer mode. If I instead use 64:

uniform mat4 T[64]

everything is fine.

Seems to be a problem with exceeding the maximum number of uniforms. But as I wrote above I'm getting 4096 for GL_MAX_VERTEX_UNIFORM_COMPONENTS so 4096/(4*4) = 256 not 64...

OpenGL.org wiki says

ATI/AMD note: The ATI max component values are wrong. They are the actual number of components divided by 4.

But reading this I would think that if I query GL_MAX_VERTEX_UNIFORM_COMPONENTS and get 4096 that I actually have 16,384. What seems to be the case is that GL_MAX_VERTEX_UNIFORM_COMPONENTS returns the actual number of components multiplied by 4. This would then give 1024/(4*4) = 64.

Can anyone confirm this?

Edit:
My shader is simply:

#version 120

// 65 goes into software render mode
#define MAX_T 64
attribute vec4 indices;
uniform mat4 T[MAX_T];

void main()
{
  gl_Position =  T[int(indices[0])]*gl_Vertex;
}

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