#extension GL_EXT_frag_depth : enable

// 
// adapted from the EDL shader code from Christian Boucheny in cloud compare:
// https://github.com/cloudcompare/trunk/tree/master/plugins/qEDL/shaders/EDL
//

precision mediump float;
precision mediump int;

//uniform float screenWidth;
//uniform float screenHeight;
uniform vec2 resolution;


uniform vec2 neighbours[NEIGHBOUR_COUNT];
uniform float edlStrength;
uniform float radius;
uniform float opacity;

//uniform float uNear;
//uniform float uFar;

uniform mat4 uProj;

uniform sampler2D uEDLColor;
uniform sampler2D uEDLDepth;

varying vec2 vUv;

uniform int useEDL;

float response(float depth){
	vec2 uvRadius = radius / resolution;             //vec2(screenWidth, screenHeight);
	
	float sum = 0.0;
	
	for(int i = 0; i < NEIGHBOUR_COUNT; i++){
		vec2 uvNeighbor = vUv + uvRadius * neighbours[i];
		//获取周围八个格子的值
		float neighbourDepth = texture2D(uEDLColor, uvNeighbor).a;
		neighbourDepth = (neighbourDepth == 1.0) ? 0.0 : neighbourDepth;

		if(neighbourDepth != 0.0){
			 //if(depth == 0.0){
			 //	sum += 100.0;
			 //}else{
				sum += max(0.0, depth - neighbourDepth);  //获取差值
			 //}
		}
	}
	
	return sum / float(NEIGHBOUR_COUNT);
}

void main(){
	vec4 cEDL = texture2D(uEDLColor, vUv);
	
	float depth = cEDL.a;
	depth = (depth == 1.0) ? 0.0 : depth;
    
    if(depth == 0.0){ //去掉这句就能在无点云像素的地方渲染outline，但会遮住其他mesh
		discard;
	}
    
    
    if(useEDL == 1){
        float res = response(depth); 
        float shade = exp(-res * 300.0 * edlStrength); //自然常数e为底的指数函数 
        const float min = 0.2; //add 使边缘色变浅  范围从0-1 变为min-1
        shade = shade * (1.0-min) + min;
        gl_FragColor = vec4(cEDL.rgb * shade, opacity);  
    }else{//加  不改颜色的情况 
        gl_FragColor = vec4(cEDL.rgb, opacity);
    } 
    //注意，edlStrength越强，在相同depth的叠放的点云间的轮廓线颜色越深
    //作用：勾勒边缘，强化深度差异，模拟阴影，加强结构立体感
    
    { // write regular hyperbolic depth values to depth buffer  修改深度
        float dl = pow(2.0, depth);

        vec4 dp = uProj * vec4(0.0, 0.0, -dl, 1.0);
        float pz = dp.z / dp.w;
        float fragDepth = (pz + 1.0) / 2.0;

        gl_FragDepthEXT = fragDepth;
    }
	
}