layered_perlin_noise_1d.shader

Shader "Tutorial/027_layered_noise/1d" {
	Properties {
		_CellSize ("Cell Size", Range(0, 2)) = 2
		_Roughness ("Roughness", Range(1, 8)) = 3
		_Persistance ("Persistance", Range(0, 1)) = 0.4
	}
	SubShader {
		Tags{ "RenderType"="Opaque" "Queue"="Geometry"}

		CGPROGRAM

		#pragma surface surf Standard fullforwardshadows
		#pragma target 3.0

		#include "Random.cginc"

		//global shader variables
		#define OCTAVES 4 

		float _CellSize;
		float _Roughness;
		float _Persistance;

		struct Input {
			float3 worldPos;
		};

		float easeIn(float interpolator){
			return interpolator * interpolator * interpolator * interpolator * interpolator;
		}

		float easeOut(float interpolator){
			return 1 - easeIn(1 - interpolator);
		}

		float easeInOut(float interpolator){
			float easeInValue = easeIn(interpolator);
			float easeOutValue = easeOut(interpolator);
			return lerp(easeInValue, easeOutValue, interpolator);
		}

		float gradientNoise(float value){
			float fraction = frac(value);
			float interpolator = easeInOut(fraction);

			float previousCellInclination = rand1dTo1d(floor(value)) * 2 - 1;
			float previousCellLinePoint = previousCellInclination * fraction;

			float nextCellInclination = rand1dTo1d(ceil(value)) * 2 - 1;
			float nextCellLinePoint = nextCellInclination * (fraction - 1);

			return lerp(previousCellLinePoint, nextCellLinePoint, interpolator);
		}

		float sampleLayeredNoise(float value){
			float noise = 0;
			float frequency = 1;
			float factor = 1;

			[unroll]
			for(int i=0; i<OCTAVES; i++){
				noise = noise + gradientNoise(value * frequency + i * 0.72354) * factor;
				factor *= _Persistance;
				frequency *= _Roughness;
			}

			return noise;
		}

		void surf (Input i, inout SurfaceOutputStandard o) {
			float value = i.worldPos.x / _CellSize;
			float noise = sampleLayeredNoise(value);
			
			float dist = abs(noise - i.worldPos.y);
			float pixelHeight = fwidth(i.worldPos.y);
			float lineIntensity = smoothstep(2*pixelHeight, pixelHeight, dist);
			o.Albedo = lerp(1, 0, lineIntensity);
		}
		ENDCG
	}
	FallBack "Standard"
}