第 15 课：Fresnel Reflectance

实现：D × G × F

实现

uniform vec2 iResolution;
uniform float iTime;
uniform sampler2D iChannel0;
uniform sampler2D iChannel1;
uniform sampler2D iChannel2;
uniform mat4 inverseViewMatrix;

varying vec3 vPos;
varying vec3 vNormal;
varying vec2 vUv;

vec3 fresnelSchlick(float cosTheta, vec3 F0) {
	float clampedCos = clamp(1.0 - cosTheta, 0.0, 1.0);
    return F0 + (1.0 - F0) * pow(1.0 - clampedCos, 5.0);
}

vec3 getViewPos() {
  return (inverseViewMatrix * vec4(0.0, 0.0, 0.0, 1.0)).xyz;
}

void main() {
  vec3 viewPos = getViewPos();

  vec3 fragColor = vec3(1.0, 0.6, 0.6);
  vec3 fragNormal = normalize(vNormal);
  float fragMetallic = 0.0;

  vec3 fragPos = vPos;
  vec3 lightColor = vec3(1.0, 1.0, 1.0);
  vec3 lightPos = vec3(0.0, 0.5, -0.6);
  vec3 lightDir = normalize(lightPos - fragPos);
  vec3 viewDir = normalize(viewPos - fragPos);
  vec3 halfwayDir = normalize(viewDir + lightDir);

  float shininess = 8.0;
  float specular = pow(max(dot(fragNormal, halfwayDir), 0.0),  shininess);
  float NoL = max(dot(fragNormal, lightDir), 0.0);
  float NoV = max(dot(halfwayDir, viewDir), 0.0);

  // Base Reflectance
  vec3 F0 = vec3(0.04);

  vec3 kS = fresnelSchlick(NoV, F0);
  vec3 kD = vec3(1.0) - kS;

  gl_FragColor = vec4(fragColor * NoL * lightColor * kD + specular * kS * lightColor, 1.0);
}

复盘笔记

• D × G × F
• F = Fresnel Reflectance
• ![[Pasted image 20251205001407.png]]
• ![[Pasted image 20251205002056.png]]