GLSL：片段着色器什么时候退出/返回

Question

假设我们有以下片段着色器：

varying vec2 vUv; // uv coordinates
varying float vTexture; // texture index in array of textures

uniform sampler2D textures[2]; // number of textures

void main() {
  int textureIndex = int(floor(vTexture)); // convert texture index to int for equality checks

  if (textureIndex == 0) {
    gl_FragColor = texture2D(textures[0], vUv);
  }

  if (textureIndex == 1) {
    gl_FragColor = texture2D(textures[1], vUv);
  } 
}

如果通过此着色器的给定值具有textureIndex = 0，那么该值是否会检查第二个if条件，还是gl_FragColor的建立会导致main()函数“返回”还是退出？有没有办法强制片段着色器在给定点退出或返回？

Answer 1

新答案（特定于问题）

void main() {
  int textureIndex = int(floor(vTexture)); // convert texture index to int for equality checks

  if (textureIndex == 0) {
    gl_FragColor = texture2D(textures[0], vUv);
  }

  if (textureIndex == 1) {
    gl_FragColor = texture2D(textures[1], vUv);
  } 

  // <--- HERE (ONCE IT RUNS THE CODE ABOVE, IT REACHES THE "END" AND EXITS)

}