Raymarched shadertoy clouds in Unity (SPI ready)

iqcloudsSPI.shader

Shader "Custom/Raymarcher4"
{
  // based on MichaelPohoreski's no-noise texture variation of iq's brilliant https://www.shadertoy.com/view/XslGRr
  // code is a mess. Reader beware. 
  // wanted to put it out there as a quick & dirty example of raymarching in Unity, since info is scarce. 
  // of particular note: SPI macros for instancing on stereoscopic devices, and the rewritten camera logic (no more rays-through-uvs, we're in "real" camera land now!)
  // hope this is useful!
  
	Properties
	{

	}
	SubShader
	{
		Tags { "Queue" = "Transparent" }
		Blend SrcAlpha OneMinusSrcAlpha

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma multi_compile_instancing
			#include "UnityCG.cginc"
			#include "UnityLightingCommon.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				UNITY_VERTEX_INPUT_INSTANCE_ID
				float2 uv : TEXCOORD0;
			};

			struct v2f
			{
				float3 wPos : float3;
				float4 v: float4;
				float4 pos : SV_POSITION;
				UNITY_VERTEX_OUTPUT_STEREO
			};

			UNITY_INSTANCING_BUFFER_START(Props)
			UNITY_INSTANCING_BUFFER_END(Props)

				v2f vert(appdata v)
			{
				v2f o;
				UNITY_SETUP_INSTANCE_ID(v);
				UNITY_INITIALIZE_OUTPUT(v2f, o);
				UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
				o.pos = UnityObjectToClipPos(v.vertex);
				o.v = v.vertex;
				o.wPos = mul(unity_ObjectToWorld, v.vertex).xyz;
				return o;
			}

			float iqhash(float n)
			{
				return frac(sin(n) * 43758.5453);
			}

			float noise(float3 x)
			{
				float3 p = floor(x);
				float3 f = frac(x);
				f = f * f * (3.0 - 2.0 * f);
				float n = p.x + p.y * 57.0 + 113.0 * p.z;
				return lerp(lerp(lerp(iqhash(n + 0.0), iqhash(n + 1.0), f.x),
							   lerp(iqhash(n + 57.0), iqhash(n + 58.0), f.x), f.y),
							   lerp(lerp(iqhash(n + 113.0), iqhash(n + 114.0), f.x),
							   lerp(iqhash(n + 170.0), iqhash(n + 171.0), f.x), f.y), f.z);
			}

			//change: factor in headpose

			float map5(in float3 p, in float3 ro)
			{
				float3 q = p - float3(0.0, 0.1, 1.0) * _Time.y / 3;
				float f;
				f = 0.50000 * noise(q); q = q * 2.02;
				f += 0.25000 * noise(q); q = q * 2.03;
				f += 0.12500 * noise(q); q = q * 2.01;
				f += 0.06250 * noise(q); q = q * 2.02;
				f += 0.03125 * noise(q);
				return saturate(1.5 - p.y - 2.0 + 1.75 * f + ro.y - .9);
			}

			float map4(in float3 p, in float3 ro)
			{
				float3 q = p - float3(0.0, 0.1, 1.0) * _Time.y;
				float f;
				f = 0.50000 * noise(q); q = q * 2.02;
				f += 0.25000 * noise(q); q = q * 2.03;
				f += 0.12500 * noise(q); q = q * 2.01;
				f += 0.06250 * noise(q);
				return saturate(1.5 - p.y - 2.0 + 1.75 * f + ro.y - .7);
			}
			float map3(in float3 p, in float3 ro)
			{
				float3 q = p - float3(0.0, 0.1, 1.0) * _Time.y;
				float f;
				f = 0.50000 * noise(q); q = q * 2.02;
				f += 0.25000 * noise(q); q = q * 2.03;
				f += 0.12500 * noise(q);
				return saturate(1.5 - p.y - 2.0 + 1.75 * f + ro.y - .7);
			}
			float map2(in float3 p, in float3 ro)
			{
				float3 q = p - float3(0.0, 0.1, 1.0) * _Time.y;
				float f;
				f = 0.50000 * noise(q); q = q * 2.02;
				f += 0.25000 * noise(q);
				return saturate(1.5 - p.y - 2.0 + 1.75 * f + ro.y - .7);
			}

			float4 integrate(in float4 sum, in float dif, in float den, in float3 bgcol, in float t)
			{
				// lighting
				float3 lin = float3(0.65, 0.7, 0.75) * 1.4 + float3(1.0, 0.6, 0.3) * dif;
				float4 col = float4(lerp(float3(1.0, 0.95, 0.8), float3(0.25, 0.3, 0.35), den), den);
				//col.xyz *= lin;
				col.xyz *= lin;
				col.xyz = lerp(col.xyz, bgcol, 1.0 - exp(-.0001 * t * t));
				// front to back blending    
				col.a *= 0.4;
				col.rgb *= col.a;
				return sum + col * (1.0 - sum.a);
			}

			#define MARCH(STEPS,MAPLOD, ro) for(int i=0; i<STEPS; i++) { float3  pos = ro + t*rd; if(  sum.a > 0.99 ) break; float den = MAPLOD( pos, ro ); if( den>0.01 ) { float dif =  saturate((den - MAPLOD(pos+0.3*_WorldSpaceLightPos0.xyz,ro))/0.6); sum = integrate( sum, dif, den, bgcol, t ); } t += max(4.05,0.02*t); }

			float4 raymarch(in float3 ro, in float3 rd, in float3 bgcol)
			{
				float4 sum = float4(0.0,0.0,0.0,0.0);

				float t = 0.0;//0.05*texelFetch( iChannel0, px&255, 0 ).x;

				MARCH(5, map5, ro);
				//MARCH(30, map4, ro);
				//MARCH(30, map3, ro);
				//MARCH(30, map2, ro);

				return saturate(sum);
			}

			float4 render(in float3 ro, in float3 rd)
			{
				// background sky     
				float sun = saturate(dot(_WorldSpaceLightPos0.xyz, rd));
				//float3 col = float3(0.6, 0.71, 0.75) - rd.y * 0.2 * float3(1.0, 0.5, 1.0) + 0.15 * 0.5;
				float3 col = float3(.0, .0, .0);
				//col += 0.2 * float3(1.0, .6, 0.1) * pow(sun, 8.0);

				// clouds    
				float4 res = raymarch(ro, rd, col);
				col = col * (1.0 - res.w) + res.xyz;

				// sun glare    
				col += 0.2 * float3(1.0, 0.4, 0.2) * pow(sun, 3.0);
				if (col.x < .2)
				{
					//discard;
				}
				else {
					//col *= 2;
				}
				return float4(col, 1.0);
			}



			float opScale(float3 p, float s)
			{
				//return MandelBulb(p / s, 17) * s;
			}

			fixed4 frag(v2f i) : SV_Target
			{
				float4 objectOrigin = mul(unity_ObjectToWorld, float4(0.0,0.0,0.0,1.0));
				float3 viewDirection = normalize(i.wPos - _WorldSpaceCameraPos);
				float3 worldPosition = i.wPos;
				float3 ro = _WorldSpaceCameraPos;
				float3 rd = viewDirection;
				//float curDistance = 5. - distance(objectOrigin.xyz, i.v);
				fixed4 r = render(ro, rd);
				return fixed4(r.xyz,1.);
			}
			ENDCG
			}
	}
}