//     Weedシェーダ
//        ver 1.2 2020/12/02
//        by yarunashi@dooon

// xs_begin
// author : 'yarunashi@dooon'
// arg : { id = '0' name = 'rate' value = '0.3' range = '0.1 1.0' step = '0.1'	decimal = '1' }
// arg : { id = '1' name = 'range' value = '2' range = '1 2' step = '1'	decimal = '0' }
// arg : { id = '2' name = 'seed' value = '1' range = '0 1000' step = '1'	decimal = '0' }
// xs_end

float rate = i_args[0]; 
float range = i_args[1]; 
float seed = i_args[2]; 

float rand(vec2 co, float seed) {
	return fract(sin(dot(co.xy * seed, vec2(12.9898, 78.233))) * 43758.5453);
}
float rand3(vec3 v, float seed) { 
    float r = rand(vec2(v.x, v.y), seed);
    r = rand(vec2(r, v.z), seed);
	return r;
}

float weight(vec3 v, float rng){
    float K = rng;
    float cnt = 0.0;
    float sum = 0.0;

    for(float z = -K; z <= K; z++)
    for(float y = -K; y <= K; y++)
    for(float x = -K; x <= K; x++) {
        if (voxel(vec3(v.x + x, v.y + y, v.z + z)) > 0.0) sum++;
        cnt++;
    }
    return sum / cnt;
}

float map(vec3 v) {  
    float i = voxel(v);
    if ( i > 0.0) return i;
	if ((rand3(v, seed) < (rate * 0.1)) && (weight(v, range) > 0.0)) {
		return i_color_index;
	}
	return 0.0;
}