Question

之前我曾使用着色器做过一些工作，但我认为自己对GLSL相对缺乏经验。我正在尝试使用一系列片段着色器编写模拟烟雾的流体求解器。其中大多数涉及从纹理中获取离散样本，然后对它们进行一些操作，因此它们都具有类似的编译错误。必须对每个像素和每个像素进行评估，因此我使用texelFetch而不是texture2D进行采样。以下是此类片段着色器的示例：

uniform sampler2D velocity;
uniform sampler2D pressure;
uniform sampler2D solid;
uniform float numCellsX;
uniform float numCellsY;

void main(void) {
    ivec2 pos = ivec2(gl_FragCoord.xy);
    if (texelFetch(solid, pos.xy, 0).x > 0.0)
        discard;

    float c = texelFetch(pressure, pos.xy, 0).x;
    float up = texelFetchOffset(pressure, pos.xy, 0, ivec2(0, 1)).x;
    float down = texelFetchOffset(pressure, pos.xy, 0, ivec2(0, -1)).x;
    float left = texelFetchOffset(pressure, pos.xy, 0, ivec2(-1, 0)).x;
    float right = texelFetchOffset(pressure, pos.xy, 0, ivec2(1, 0)).x;

    float upS = texelFetchOffset(solid, pos.xy, 0, ivec2(0, 1)).x;
    float downS = texelFetchOffset(solid, pos.xy, 0, ivec2(0, -1)).x;
    float leftS = texelFetchOffset(solid, pos.xy, 0, ivec2(-1, 0)).x;
    float rightS = texelFetchOffset(solid, pos.xy, 0, ivec2(1, 0)).x;

    if (upS > 0.0) up = c;
    if (downS > 0.0) down = c;
    if (leftS > 0.0) left = c;
    if (rightS > 0.0) right = c;

    gl_FragColor = texelFetch(velocity, pos.xy, 0) - vec2(0.5 * numCellsX * (right - left), 0.5 * numCellsY * (up - down));
}

当我通过glSlangValidator运行时，我收到以下错误：

ERROR: 0:14: 'texelFetch' : no matching overloaded function found
ERROR: 0:14: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:17: 'texelFetch' : no matching overloaded function found
ERROR: 0:17: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:18: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:18: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:19: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:19: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:20: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:20: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:21: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:21: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:23: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:23: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:24: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:24: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:25: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:25: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:26: 'texelFetchOffset' : no matching overloaded function found
ERROR: 0:26: 'scalar swizzle' : not supported with this profile: es
ERROR: 0:33: 'texelFetch' : no matching overloaded function found
ERROR: 0:33: 'assign' :  cannot convert from 'temp 2-component vector of float'
to 'fragColor mediump 4-component vector of float FragColor'
ERROR: 23 compilation errors.  No code generated.

几乎每一行都有一个错误，我在网上找到的关于这些事情的信息非常少。根据GLSL参考手册：

gvec4 texelFetch(gsampler2D sampler, ivec2 P, int lod);

我不太明白为什么它不接受我的texelFetch调用。我也不知道标量混合是什么（在网上找不到这个）或为什么会出现问题。

Answer 1

此配置文件不支持：es

也许你应该用桌面版的GLSL编译它，而不是GLSL ES（大概是2.0）。您应该始终在GLSL着色器中使用#version声明。

此外，如果您使用的是texelFetch，为什么还要撰写gl_FragColor等弃用的输出？

然而：

无法转换为'float'的临时双组分向量

无论此行的版本如何，都是如此：

texelFetch(velocity, pos.xy, 0) - vec2(0.5 * numCellsX * (right - left), 0.5 * numCellsY * (up - down))

texelFetch返回一个4元素向量。您不能从4元素向量中减去2元素向量。

GLSL中TexelFetch和“Scalar Swizzle”的问题

1 个答案: