第 16 课：Matallic Reflectance

实现：应该是混合metallic+fresnelSchlick

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 = 1.0;

  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);

  // Phong Specular Component
  float shininess = 8.0;
  float specular = pow(max(dot(fragNormal, halfwayDir), 0.0),  shininess);
  float NoL = dot(fragNormal, lightDir);

  // Base Reflectance
  vec3 F0 = vec3(0.04);
  F0 = mix(F0, fragColor, fragMetallic);

  // Fresnel-Schlick Approximation
  vec3 kS = fresnelSchlick(max(dot(halfwayDir, viewDir), 0.0), F0);
  vec3 kD = vec3(1.0) - kS;

  vec3 d = fragColor * NoL * lightColor * kD * (1.0-fragMetallic);
  vec3 s = specular * lightColor * kS;

  gl_FragColor = vec4(d + s, 1.0);
}

复盘笔记

• 应该是混合metallic+fresnelSchlick