TouhouGD/tools/MagicaVoxel-0.99.6.4-win64/shader/corrosion.txt

// MIT License (MIT)
// Copyright (c) 2020 Patrick Seeber
//
// xs_begin
// author : '@rubikow'
// arg : { id = '0'  name = 'Max Volume'  value = '4'  range = '0 100'  step = '1'  decimal = '0' }
// arg : { id = '1'  name = 'Random Seed'  value = '123'  range = '0 10000'  step = '1'  decimal = '2' }
// arg : { id = '2'  name = 'Growth Density'  value = '0.3'  range = '0 1'  step = '0.01'  decimal = '2' }
// arg : { id = '3'  name = 'Additional Colors'  value = '0'  range = '-255 255'  step = '1'  decimal = '0' }
// xs_end

float thickness = float(iArgs[0]);
float seed = float(iArgs[1]);
float density = float(iArgs[2]);
float colorRange = float(iArgs[3]);

bool isGrowColor(vec3 v){
	return voxel(v) >= min(i_color_index, i_color_index + colorRange) && voxel(v) <= max(i_color_index, i_color_index + colorRange);
}

float random(vec3 v, float seed){
	float n = v.x*v.y*v.z + seed;

	return abs(fract(sin(1./tan(n) + seed * 1235.342)));
}

float minDistanceToWall(vec3 v, float distance){
	
	float minDistance = distance+1.;
	
	for(int x=-int(distance); x<=int(distance);x++){
		for(int y=-int(distance); y<=int(distance);y++){
			for(int z=-int(distance); z<=int(distance);z++){								
				if(voxel(vec3(v.x+float(x),v.y+float(y),v.z+float(z))) != 0. && !isGrowColor(vec3(v.x+float(x),v.y+float(y),v.z+float(z)))){
					float d = sqrt(pow(float(x),2.) + pow(float(y),2.) + pow(float(z),2.));
					if(minDistance > d){
						minDistance = d;
					}					
				}
			}			
		}		
	}
	
	return minDistance;
}

float getCrowColor(vec3 v){
	float distance = minDistanceToWall(v, thickness);	
	return i_color_index + colorRange * (distance/sqrt(pow(thickness,2.)*3.));
}

bool hasWallNextToIt(vec3 v, float distance){
	
	for(int x=-int(distance); x<=int(distance);x++){
		for(int y=-int(distance); y<=int(distance);y++){
			for(int z=-int(distance); z<=int(distance);z++){								
				if(voxel(vec3(v.x+float(x),v.y+float(y),v.z+float(z))) != 0. && !isGrowColor(vec3(v.x+float(x),v.y+float(y),v.z+float(z))) ){
					return true;
				}				
			}			
		}		
	}
	
	return false;
}

int getFlatNeighbors(vec3 v){
	int neighbors = 0;

	if(isGrowColor(vec3(v.x+1.,v.y+1.,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x+1.,v.y-1.,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x-1.,v.y+1.,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x-1.,v.y-1.,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x+1.,v.y,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x-1.,v.y,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x,v.y-1.,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x,v.y+1.,v.z))){							
		neighbors++;			
	}

	return neighbors;
}

int getNeighbors(vec3 v){
	int neighbors = 0;

	if(isGrowColor(vec3(v.x,v.y,v.z+1.))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x,v.y,v.z-1.))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x+1.,v.y,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x-1.,v.y,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x,v.y-1.,v.z))){							
		neighbors++;			
	}
	if(isGrowColor(vec3(v.x,v.y+1.,v.z))){							
		neighbors++;			
	}

	return neighbors;
}

bool growsDown(vec3 v){	

	if(isGrowColor(vec3(v.x,v.y,v.z+1.))){							
		return true;
	}
	if(isGrowColor(vec3(v.x+1.,v.y,v.z))){							
		return true;
	}
	if(isGrowColor(vec3(v.x-1.,v.y,v.z))){							
		return true;
	}
	if(isGrowColor(vec3(v.x,v.y-1.,v.z))){							
		return true;
	}
	if(isGrowColor(vec3(v.x,v.y+1.,v.z))){							
		return true;
	}
	
	return false;
}

bool grows(vec3 v){
	int n = getNeighbors(v);
	float r = random(v, seed+float(n));
	if(voxel(v) != 0.){				
		if(hasWallNextToIt(v, 1.) && isGrowColor(v+vec3(0,0,-1.))  && mod(v.x+v.y,13.) == 0.){
			return true;
		}
		if(hasWallNextToIt(v, 1.) && isGrowColor(v+vec3(0,0,1.)) && mod(v.x+v.y,27.) == 0.){
			return true;
		}
		if(hasWallNextToIt(v, 1.) && isGrowColor(v+vec3(0,0,-2.)) && mod(v.x+v.y,13.) == 0.){
			return true;
		}		
		if(hasWallNextToIt(v, 1.) && isGrowColor(v+vec3(0,0,2.)) && mod(v.x+v.y,27.) == 0.){
			return true;
		}
		
		if(hasWallNextToIt(v, 1.) && getFlatNeighbors(v) > 3){
			return true;
		}
		else if(r < (density) - (minDistanceToWall(v,thickness)/thickness)*(density/2.) && hasWallNextToIt(v, thickness) && n > 0 && (growsDown(v) || random(v, seed+5.567) < 0.3)) 
		{
			return true;
		}		
	}
	
	return false;
}

float grow(vec3 v, float seed){	
	if( grows(v)){
		return getCrowColor(v);		
	}else if(isGrowColor(v) && minDistanceToWall(v, thickness) > 1.){
		int n = getNeighbors(v);
		float r = random(v, seed+float(n));
		if((r < density + float(n)/10. + (pow(minDistanceToWall(v, thickness),2.)/pow(thickness,2.)) * 0.5)){
			return 0.;
		}
	}
	return voxel(v);
}

float map(vec3 v) {
	return grow(v, seed);
}