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- // Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
-
- // Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
-
-
- Shader "Atmosphere/SkyFromSpace"
- {
- SubShader
- {
- Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
- //Tags { "RenderType"="Opaque" }
- Pass
- {
-
- Blend SrcAlpha OneMinusSrcAlpha
- ZWrite Off
- Cull Front
- //Blend One One
-
- CGPROGRAM
- #include "UnityCG.cginc"
- #pragma target 3.0
- #pragma vertex vert
- #pragma fragment frag
-
- uniform float3 v3Translate; // The objects world pos
- uniform float3 v3LightPos; // The direction vector to the light source
- uniform float3 v3InvWavelength; // 1 / pow(wavelength, 4) for the red, green, and blue channels
- uniform float fOuterRadius; // The outer (atmosphere) radius
- uniform float fOuterRadius2; // fOuterRadius^2
- uniform float fInnerRadius; // The inner (planetary) radius
- uniform float fInnerRadius2; // fInnerRadius^2
- uniform float fKrESun; // Kr * ESun
- uniform float fKmESun; // Km * ESun
- uniform float fKr4PI; // Kr * 4 * PI
- uniform float fKm4PI; // Km * 4 * PI
- uniform float fScale; // 1 / (fOuterRadius - fInnerRadius)
- uniform float fScaleDepth; // The scale depth (i.e. the altitude at which the atmosphere's average density is found)
- uniform float fScaleOverScaleDepth; // fScale / fScaleDepth
- uniform float fHdrExposure; // HDR exposure
- uniform float g; // The Mie phase asymmetry factor
- uniform float g2; // The Mie phase asymmetry factor squared
-
- struct v2f
- {
- float4 pos : SV_POSITION;
- float2 uv : TEXCOORD0;
- float3 t0 : TEXCOORD1;
- float3 c0 : COLOR0;
- float3 c1 : COLOR1;
- };
-
- float scale(float fCos)
- {
- float x = 1.0 - fCos;
- return 0.25 * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));
- }
-
-
- v2f vert(appdata_base v)
- {
-
- float3 v3CameraPos = _WorldSpaceCameraPos - v3Translate; // The camera's current position
- float fCameraHeight = length(v3CameraPos); // The camera's current height
- float fCameraHeight2 = fCameraHeight*fCameraHeight; // fCameraHeight^2
-
- // Get the ray from the camera to the vertex and its length (which is the far point of the ray passing through the atmosphere)
- float3 v3Pos = mul(unity_ObjectToWorld, v.vertex).xyz - v3Translate;
- float3 v3Ray = v3Pos - v3CameraPos;
- float fFar = length(v3Ray);
- v3Ray /= fFar;
-
- // Calculate the closest intersection of the ray with the outer atmosphere (which is the near point of the ray passing through the atmosphere)
- float B = 2.0 * dot(v3CameraPos, v3Ray);
- float C = fCameraHeight2 - fOuterRadius2;
- float fDet = max(0.0, B*B - 4.0 * C);
- float fNear = 0.5 * (-B - sqrt(fDet));
-
- // Calculate the ray's start and end positions in the atmosphere, then calculate its scattering offset
- float3 v3Start = v3CameraPos + v3Ray * fNear;
- fFar -= fNear;
- float fStartAngle = dot(v3Ray, v3Start) / fOuterRadius;
- float fStartDepth = exp(-1.0/fScaleDepth);
- float fStartOffset = fStartDepth*scale(fStartAngle);
-
- const float fSamples = 2.0;
-
- // Initialize the scattering loop variables
- float fSampleLength = fFar / fSamples;
- float fScaledLength = fSampleLength * fScale;
- float3 v3SampleRay = v3Ray * fSampleLength;
- float3 v3SamplePoint = v3Start + v3SampleRay * 0.5;
-
- // Now loop through the sample rays
- float3 v3FrontColor = float3(0.0, 0.0, 0.0);
- for(int i=0; i<int(fSamples); i++)
- {
- float fHeight = length(v3SamplePoint);
- float fDepth = exp(fScaleOverScaleDepth * (fInnerRadius - fHeight));
- float fLightAngle = dot(v3LightPos, v3SamplePoint) / fHeight;
- float fCameraAngle = dot(v3Ray, v3SamplePoint) / fHeight;
- float fScatter = (fStartOffset + fDepth*(scale(fLightAngle) - scale(fCameraAngle)));
- float3 v3Attenuate = exp(-fScatter * (v3InvWavelength * fKr4PI + fKm4PI));
- v3FrontColor += v3Attenuate * (fDepth * fScaledLength);
- v3SamplePoint += v3SampleRay;
- }
-
- v2f OUT;
- OUT.pos = UnityObjectToClipPos(v.vertex);
- OUT.uv = v.texcoord.xy;
-
- // Finally, scale the Mie and Rayleigh colors and set up the varying variables for the pixel shader
- OUT.c0 = v3FrontColor * (v3InvWavelength * fKrESun);
- OUT.c1 = v3FrontColor * fKmESun;
- OUT.t0 = v3CameraPos - v3Pos;
-
- return OUT;
- }
-
- // Calculates the Mie phase function
- float getMiePhase(float fCos, float fCos2, float g, float g2)
- {
- return 1.5 * ((1.0 - g2) / (2.0 + g2)) * (1.0 + fCos2) / pow(1.0 + g2 - 2.0*g*fCos, 1.5);
- }
-
- // Calculates the Rayleigh phase function
- float getRayleighPhase(float fCos2)
- {
- return 0.75 + 0.75*fCos2;
- }
-
- half4 frag(v2f IN) : COLOR
- {
- float fCos = dot(v3LightPos, IN.t0) / length(IN.t0);
- float fCos2 = fCos*fCos;
- float3 col = getRayleighPhase(fCos2) * IN.c0 + getMiePhase(fCos, fCos2, g, g2) * IN.c1;
-
- col = 1.0 - exp(col * -fHdrExposure);
-
- return float4(col,col.b);
- }
-
- ENDCG
-
- }
- }
- }
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