107 lines
2.8 KiB
HLSL
107 lines
2.8 KiB
HLSL
// Copyright Epic Games, Inc. All Rights Reserved.
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#pragma once
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struct FCapsuleLight
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{
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float3 LightPos[2];
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float Length;
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float Radius;
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float SoftRadius;
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float DistBiasSqr;
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};
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void ClipToHorizon( inout float3 Line0, inout float3 Line1, float3 N )
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{
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float NoP0 = dot( N, Line0 );
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float NoP1 = dot( N, Line1 );
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if( NoP0 < 0 ) Line0 = ( Line0 * NoP1 - Line1 * NoP0 ) / ( NoP1 - NoP0 );
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if( NoP1 < 0 ) Line1 = ( -Line0 * NoP1 + Line1 * NoP0 ) / ( -NoP1 + NoP0 );
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}
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// Closest point on line segment to point
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float3 ClosestPointLineToPoint( float3 Line0, float3 Line1, float Length )
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{
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float3 Line01 = Line1 - Line0;
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return Line0 + Line01 * saturate( -dot( Line01, Line0 ) / Pow2( Length ) );
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}
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// Closest point on line segment to ray
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float3 ClosestPointLineToRay( float3 Line0, float3 Line1, float Length, float3 R )
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{
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float3 L0 = Line0;
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float3 L1 = Line1;
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float3 Line01 = Line1 - Line0;
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// Shortest distance
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float A = Square( Length );
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float B = dot( R, Line01 );
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float t = saturate( dot( Line0, B*R - Line01 ) / (A - B*B) );
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return Line0 + t * Line01;
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}
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float3 SmallestAnglePointOnLineToRay( float3 Line0, float3 Line1, float Length, float3 R )
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{
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float3 L0 = Line0;
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float3 L1 = Line1;
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float3 Line01 = Line1 - Line0;
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float A = Square( Length );
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float B = 2 * dot( Line0, Line01 );
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float C = dot( Line0, Line0 );
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float D = dot( R, Line0 );
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float E = dot( R, Line01 );
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float t = saturate( (B*D - 2*C*E) / (B*E - 2*A*D) );
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return Line0 + t * Line01;
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}
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void LineIrradiance( float3 Line0, float3 Line1, float DistanceBiasSqr, out float CosSubtended, out float Falloff, out half3 L )
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{
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float LengthSqr0 = dot( Line0, Line0 );
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float LengthSqr1 = dot( Line1, Line1 );
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float InvLength0 = rsqrt( LengthSqr0 );
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float InvLength1 = rsqrt( LengthSqr1 );
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float InvLength01 = InvLength0 * InvLength1;
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CosSubtended = dot( Line0, Line1 ) * InvLength01;
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Falloff = InvLength01 / ( CosSubtended * 0.5 + 0.5 + DistanceBiasSqr * InvLength01 );
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L = 0.5 * ( Line0 * InvLength0 + Line1 * InvLength1 );
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}
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// Alpha is half of angle of spherical cap
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float SphereHorizonCosWrap( float NoL, float SinAlphaSqr )
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{
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#if 1
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float SinAlpha = sqrt( SinAlphaSqr );
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if( NoL < SinAlpha )
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{
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NoL = max( NoL, -SinAlpha );
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#if 0
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// Accurate sphere irradiance
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float CosBeta = NoL;
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float SinBeta = sqrt( 1 - CosBeta * CosBeta );
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float TanBeta = SinBeta / CosBeta;
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float x = sqrt( 1 / SinAlphaSqr - 1 );
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float y = -x / TanBeta;
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float z = SinBeta * sqrt(1 - y*y);
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NoL = NoL * acos(y) - x * z + atan( z / x ) / SinAlphaSqr;
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NoL /= PI;
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#else
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// Hermite spline approximation
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// Fairly accurate with SinAlpha < 0.8
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// y=0 and dy/dx=0 at -SinAlpha
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// y=SinAlpha and dy/dx=1 at SinAlpha
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NoL = Pow2( SinAlpha + NoL ) / ( 4 * SinAlpha );
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#endif
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}
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#else
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NoL = saturate( ( NoL + SinAlphaSqr ) / ( 1 + SinAlphaSqr ) );
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#endif
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return NoL;
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} |