在webgl中调试GLSL代码

Debug GLSL code in webgl

本文关键字：GLSL 代码 调试 webgl      更新时间：2023-09-26

是否可以调试GLSL代码或从GLSL代码内打印变量值，而使用它与webgl ?three.js或scene.js包含任何这样的功能吗?

不尽然，

我通常调试GLSL的方式是输出颜色。例如，给定两个着色器，如

// vertex shader
uniform mat4 worldViewProjection;
uniform vec3 lightWorldPos;
uniform mat4 world;
uniform mat4 viewInverse;
uniform mat4 worldInverseTranspose;
attribute vec4 position;
attribute vec3 normal;
attribute vec2 texCoord;
varying vec4 v_position;
varying vec2 v_texCoord;
varying vec3 v_normal;
varying vec3 v_surfaceToLight;
varying vec3 v_surfaceToView;
void main() {
  v_texCoord = texCoord;
  v_position = (worldViewProjection * position);
  v_normal = (worldInverseTranspose * vec4(normal, 0)).xyz;
  v_surfaceToLight = lightWorldPos - (world * position).xyz;
  v_surfaceToView = (viewInverse[3] - (world * position)).xyz;
  gl_Position = v_position;
}
// fragment-shader    
precision highp float;
uniform vec4 colorMult;
varying vec4 v_position;
varying vec2 v_texCoord;
varying vec3 v_normal;
varying vec3 v_surfaceToLight;
varying vec3 v_surfaceToView;
uniform sampler2D diffuseSampler;
uniform vec4 specular;
uniform sampler2D bumpSampler;
uniform float shininess;
uniform float specularFactor;
vec4 lit(float l ,float h, float m) {
  return vec4(1.0,
              max(l, 0.0),
              (l > 0.0) ? pow(max(0.0, h), m) : 0.0,
              1.0);
}
void main() {
  vec4 diffuse = texture2D(diffuseSampler, v_texCoord) * colorMult;
  vec3 normal = normalize(v_normal);
  vec3 surfaceToLight = normalize(v_surfaceToLight);
  vec3 surfaceToView = normalize(v_surfaceToView);
  vec3 halfVector = normalize(surfaceToLight + surfaceToView);
  vec4 litR = lit(dot(normal, surfaceToLight),
                    dot(normal, halfVector), shininess);
  gl_FragColor = vec4((
  vec4(1,1,1,1) * (diffuse * litR.y
                        + specular * litR.z * specularFactor)).rgb,
      diffuse.a);
}

如果我在屏幕上没有看到任何东西，我将首先通过在末尾添加一行来改变片段着色器

gl_FragColor = vec4(1,0,0,1);  // draw red

如果我开始看到我的几何形状，那么我就知道问题可能是在片段着色器。我可以这样检查法线

gl_FragColor = vec4(v_normal * 0.5 + 0.5, 1);

如果法线看起来不错，我可以用

检查UV坐标。
gl_FragColor = vec4(v_texCoord, 0, 1);

等等…

你可以试试WebGL-Inspector

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