在webgl中调试GLSL代码

Question

是否可以在使用webgl时调试GLSL代码或从glsl代码中打印变量值？ three.js或scene.js是否包含任何此类功能？

Answer 1

并不是的，

我通常调试GLSL的方法是输出颜色。 例如，给定2个着色器

// 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);
}

如果我没有在屏幕上看到某些内容，我首先将片段着色器更改为仅在末尾添加一行

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

如果我开始看到我的几何体，那么我就知道这个问题可能在片段着色器中。 这样做我可能会检查我的法线

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

如果法线看起来没问题，我可能会检查UV坐标

gl_FragColor = vec4(v_texCoord, 0, 1);

等等...

Answer 2

您可以为此目的尝试WebGL-Inspector 。