还有片元着色器中的一段代码和上边的一个rect数组，能麻烦解释下是干什么用的吗？我注释掉也没什么问题。

#extension GL_OES_EGL_image_external : require
precision mediump float;

struct Rect {
vec4 color;
float left;
float top;
float right;
float bottom;
};

// important to include in order to use rendered Android View to gl texture
uniform samplerExternalOES u_Texture;

uniform float u_GlobalTime;

//const int MAX_RECTS = 4;
//uniform Rect u_Rects[MAX_RECTS];

varying vec2 v_TexCoordinate;

void main()
{

vec2 uv = v_TexCoordinate.xy;

vec4 primary_color = texture2D(u_Texture, uv);

// vec4 tmpColor = vec4(0.0, 0.0, 0.0, 0.0);
//
// bool set = false;
//
// for(int idx = 0; idx < MAX_RECTS; idx++) {
// if(uv.x > u_Rects[idx].left && uv.x < u_Rects[idx].right && uv.y > u_Rects[idx].top && uv.y < u_Rects[idx].bottom) {
// tmpColor += u_Rects[idx].color;
// set = true;
// }
// }
//
// if(set) {
// primary_color *= tmpColor;
// }

gl_FragColor = primary_color;

}