第 10 课：Spot Light

实现

uniform float iTime;
uniform sampler2D iChannel0;
uniform sampler2D iChannel1;

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

vec3 getSpotLightDir() {
  float dx = cos(iTime) * 0.25;
  float dy = sin(iTime) * 0.25;
  return normalize(vec3(0.0, 0.0, -1.0) + vec3(dx, dy, 0.0));
}

void main() {
  vec3 viewPos = vec3(-4.0, 0.0, 2.5);

  vec3 objectColor = texture2D(iChannel0, vUv).rgb;
  vec3 objectSpecular = texture2D(iChannel1, vUv).rgb;
  vec3 fragNormal = normalize(vNormal);
  vec3 fragPos = vPos;

  vec3 lightColor = vec3(1.0, 1.0, 0.75);
  vec3 lightPos = vec3(0.0, 0.0, 2.0);
  vec3 lightDir = normalize(lightPos - fragPos);

  float ambient = 0.2;
  float diffuse = max(dot(fragNormal, lightDir), 0.0);

  vec3 viewDir = normalize(viewPos - fragPos);
  vec3 reflectDir = reflect(-lightDir, fragNormal);
  float specular = max(dot(viewDir, reflectDir), 0.0);
  specular = pow(specular, 32.0);

  vec3 spotLightDir = getSpotLightDir();
  float theta = dot(spotLightDir, -lightDir);
  float cutOff = cos(radians(12.0));
  float intensity = step(cutOff, theta);

  diffuse *= intensity;
  specular *= intensity;

  vec3 result = vec3(0.0);
  result += ambient * objectColor;
  result += diffuse * objectColor;
  result += specular * objectSpecular;
  result *= lightColor;

  gl_FragColor = vec4(result, 1.0);
}