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Generate displacements from height tex #402

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Generate displacements from height tex #402

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525e179
AnimWavesAddFromTex - generate displacements from heights
huwb Jan 19, 2020
3549880
Docs / refactor
huwb Jan 19, 2020
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34 changes: 25 additions & 9 deletions crest/Assets/Crest/Crest/Shaders/OceanInputs/AnimWavesAddFromTex.shader
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Original file line number Diff line number Diff line change
Expand Up @@ -9,15 +9,14 @@ Shader "Crest/Inputs/Animated Waves/Add From Texture"
_MainTex("Texture", 2D) = "white" {}
_Strength( "Strength", float ) = 1
[Toggle] _HeightsOnly("Heights Only", Float) = 1
[Toggle] _GenerateDisplacementsFromHeights("Generate Displacements From Heights", Float) = 0
_GenerateDisplacementStrength("Generate Displacement Strength", Range(0, 10)) = 1
[Toggle] _SSSFromAlpha("Sub Surface Scattering (SSS) from Alpha", Float) = 0
_SSSStrength("SSS Strength", Float) = 0.5
}

SubShader
{
// base simulation runs on the Geometry queue, before this shader.
// this shader adds interaction forces on top of the simulation result.
Tags { "Queue" = "Transparent" }
Blend One One

Pass
Expand All @@ -28,15 +27,16 @@ Shader "Crest/Inputs/Animated Waves/Add From Texture"

#pragma shader_feature _HEIGHTSONLY_ON
#pragma shader_feature _SSSFROMALPHA_ON
#pragma shader_feature _GENERATEDISPLACEMENTSFROMHEIGHTS_ON

#include "UnityCG.cginc"

sampler2D _MainTex;
float4 _MainTex_ST;

float4 _MainTex_TexelSize;
float _Strength;
float _SSSStrength;

float _GenerateDisplacementStrength;
float _Weight;

struct Attributes
Expand All @@ -48,13 +48,15 @@ Shader "Crest/Inputs/Animated Waves/Add From Texture"
struct Varyings
{
float4 positionCS : SV_POSITION;
float2 uv : TEXCOORD0;
float3 positionWS : TEXCOORD0;
float2 uv : TEXCOORD1;
};

Varyings Vert(Attributes input)
{
Varyings o;
o.positionCS = UnityObjectToClipPos(input.positionOS);
o.positionWS = mul(unity_ObjectToWorld, float4(input.positionOS, 1.0)).xyz;
o.uv = TRANSFORM_TEX(input.uv, _MainTex);
return o;
}
Expand All @@ -67,16 +69,30 @@ Shader "Crest/Inputs/Animated Waves/Add From Texture"
half4 texSample = tex2D(_MainTex, input.uv);

#if _HEIGHTSONLY_ON
displacement.y = texSample.x * _Strength;
// Texture represents heights, not 3D displacements
displacement.y = texSample.x;

#if _GENERATEDISPLACEMENTSFROMHEIGHTS_ON
// Generate horizontal displacement from derivatives of height

// These derivatives aren't strictly correct - they assume there is a roughly 1:1 correspondance between
// texture sampling density (via _MainTex_TexelSize.x) and output sampling density (via ddx(input.positionWS.x)).
// I couldn't find a nice/cheap way to compute texel density (i.e. maintex texel size in world), so i'll leave
// it to a scale factor.
float height_x = tex2D(_MainTex, input.uv + float2(_MainTex_TexelSize.x, 0.0));
float height_z = tex2D(_MainTex, input.uv + float2(0.0, _MainTex_TexelSize.y));
displacement.x = _GenerateDisplacementStrength * (height_x - displacement.y) / ddx(input.positionWS.x);
displacement.z = _GenerateDisplacementStrength * (height_z - displacement.y) / ddy(input.positionWS.z);
#endif
#else
displacement.xyz = texSample.xyz * _Strength;
displacement.xyz = texSample.xyz;
#endif

#if _SSSFROMALPHA_ON
sss = texSample.x * _SSSStrength;
#endif

return _Weight * half4(displacement, sss);
return _Weight * half4(_Strength * displacement, sss);
}

ENDCG
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