// MinecraftPT — Parallax Occlusion Mapping
// Steep parallax mapping with PCF soft shadows.

#ifndef PARALLAX_GLSL
#define PARALLAX_GLSL

// Steep parallax mapping
vec2 ParallaxMapping(vec2 texcoord, vec3 viewDir){
	float height = texture(tex, texcoord).a;
	vec2 delta = viewDir.xy / viewDir.z * PARALLAX_DEPTH;

	int numLayers = max(1, int(PARALLAX_QUALITY));
	float layerDepth = 1.0 / float(numLayers);
	float currentDepth = 0.0;
	vec2 currentCoord = texcoord;

	for (int i = 0; i < numLayers; i++){
		currentCoord -= delta * layerDepth;
		height = texture(tex, currentCoord).a;
		currentDepth += layerDepth;
		if (height < currentDepth) break;
	}

	// Parallax shadow
	float shadow = 1.0;
	#ifdef PARALLAX_SHADOW
		// PCF shadow
		for (int i = 0; i < PARALLAX_SHADOW_QUALITY; i++){
			vec2 shadowCoord = currentCoord + delta * float(i) / float(PARALLAX_SHADOW_QUALITY);
			shadow *= step(currentDepth - layerDepth * float(i) / float(PARALLAX_SHADOW_QUALITY), texture(tex, shadowCoord).a);
		}
		#endif

	return currentCoord;
}

#endif