opengl '错误:GLSL 1.30及更高版本中禁止使用非常数表达式索引的采样器数组'在片段着色器中

ghhaqwfi  于 2022-12-12  发布在  其他
关注(0)|答案(4)|浏览(179)

我正在为游戏引擎编写以下片段着色器:

#version 330 core

layout (location = 0) out vec4 color;

uniform vec4 colour;
uniform vec2 light_pos;

in DATA
{
    vec4 position;
    vec2 uv;
    float tid;
    vec4 color;
} fs_in;

uniform sampler2D textures[32];

void main()
{
    float intensity = 1.0 / length(fs_in.position.xy - light_pos);

    vec4 texColor = fs_in.color;

    if(fs_in.tid > 0.0){
        int tid = int(fs_in.tid + 0.5);
        texColor = texture(textures[tid], fs_in.uv);
    }

    color = texColor * intensity;
}

texColor = texture(textures[tid], fs_in.uv);行导致在编译着色器时出现“GLSL 1.30及更高版本中禁止使用非常数表达式索引的采样器数组”表达式。
顶点着色器(如果需要)为:

#version 330 core

layout (location = 0) in vec4 position;
layout (location = 1) in vec2 uv;
layout (location = 2) in float tid;
layout (location = 3) in vec4 color;

uniform mat4 pr_matrix;
uniform mat4 vw_matrix = mat4(1.0);
uniform mat4 ml_matrix = mat4(1.0);

out DATA
{
    vec4 position;
    vec2 uv;
    float tid;
    vec4 color;
} vs_out;

void main()
{
    gl_Position = pr_matrix * vw_matrix * ml_matrix * position;
    vs_out.position = ml_matrix * position;
    vs_out.uv = uv;
    vs_out.tid = tid;
    vs_out.color = color;
}
v8wbuo2f

v8wbuo2f1#

在GLSL 3.3中,采样器阵列的索引仅允许通过整数常量表达式(参见GLSL 3.3 Spec, Section 4.1.7)。
在更现代的版本中,从GLSL 4.0开始,允许通过动态统一表达式索引采样器阵列(参见GLSL 4.0 Spec, Section 4.1.7
你实际上尝试的是通过一个变量来索引数组,这是不可能的。如果这是绝对不可避免的,你可以把2D纹理打包成一个2D数组纹理或一个3D纹理,并使用索引来寻址纹理的层(或第三维)。

ohtdti5x

ohtdti5x2#

我通过使用一点代码生成克服了这个问题:
在Javascript中,它看起来像这样:

const maxNumTextures = 32;
function makeSwitchCase (i) {
return `
  case ${i}:
    sum += texture2D(texturesArray[${i}], vUv);
    break;
`
};

const fragmentShader = `
#define numTextures ${maxNumTextures}

uniform sampler2D baseTexture;
uniform sampler2D texturesArray[numTextures];

varying vec2 vUv;

void main() {
  vec4 base = texture2D(baseTexture, vUv);
  vec4 sum = vec4(0.0);

  for (int i = 0; i < numTextures; ++i) {
    switch(i) {
      // we are not allowed to use i as index to access texture in array in current version of GLSL
      ${new Array(maxNumTextures)
        .fill(0)
        .map((_, i) => makeSwitchCase(i))
        .join('')}
      default: break;
    }
  }

  gl_FragColor = base + sum;
}
`;

注意:我们使用'来启动和停止JS中的多行字符串,使用${some_value}来为模板提供值

fkvaft9z

fkvaft9z3#

我也遇到过类似的问题。换到一个较新的版本(准确地说是#460)在我的情况下起作用了。

sbtkgmzw

sbtkgmzw4#

问题在于,在行texColor = texture(textures[tid], fs_in.uv)中,采样器阵列texturues被给予非恒定索引。
简单的解决方法是使用一个大的switch语句来替换texColor = texture(textures[tid], fs_in.uv)行,这样纹理数组就可以用一个常数来评估。例如,你可以这样写:

uniform sampler2D textures[32];

void main()
{
    float intensity = 1.0 / length(fs_in.position.xy - light_pos);

    vec4 texColor = fs_in.color;

    if(fs_in.tid > 0.0){
        int tid = int(fs_in.tid + 0.5);
        switch (int(tid)){
            case 0:
                texColor = texture(textures[0], fs_in.uv);
                break;
            case 1:
                texColor = texture(textures[1], fs_in.uv);
                break;
            case 2:
                texColor = texture(textures[2], fs_in.uv);
                break;
    
            // repeat for all textures
        }
    }

    color = texColor * intensity;
}

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