cocos-creator-template/assets/chunks/builtin/internal/alpha-test.chunk

// you can write GLSL code directly in here

#if USE_ALPHA_TEST
  uniform ALPHA_TEST_DATA {
    float alphaThreshold;
  };
#endif

void ALPHA_TEST (in vec4 color) {
  #if USE_ALPHA_TEST
    if (color.a < alphaThreshold) discard;
  #endif
}

void ALPHA_TEST (in float alpha) {
  #if USE_ALPHA_TEST
    if (alpha < alphaThreshold) discard;
  #endif
}