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Refactor shadowcaster to use explicit plane basis

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Replaces the use of world-to-local matrices for shadowcaster planes with explicit plane origin, basis, and normal vectors in both C# and shader code. Updates property setting in ShadowcasterUpdater and its editor preview, and rewrites the shadow sampling function in the shader include to use the new basis. Adjusts all affected shaders to use the new properties and sampling function for improved clarity and flexibility.
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DeMuenu
2025-10-01 13:26:33 +02:00
parent 841d99ad0e
commit 0e633983cf
5 changed files with 225 additions and 191 deletions
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62
Shader/Includes/Shadowcaster.cginc
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@@ -3,54 +3,30 @@
#include "UnityCG.cginc" // for tex2Dlod, etc.
static const float EPS = 1e-5;
static const float WS_EPS = 1e-5;
// Returns whether segment hits the unit plane quad in plane-local z=0.
// Outputs uv in [0,1] and t in [0,1] along A->B.
inline bool RaySegmentHitsPlaneQuad(float4x4 worldToLocal, float3 rayOrigin, float3 rayEnd, out float2 uv, out float t)
inline float4 SampleShadowcasterPlaneWS_Basis(
float3 A, float3 B,
float3 P0, float3 Uinv, float3 Vinv, float3 N,
sampler2D tex, float4 OutsideColor, float4 ShadowColor)
{
float3 aP = mul(worldToLocal, float4(rayOrigin, 1)).xyz;
float3 bP = mul(worldToLocal, float4(rayEnd, 1)).xyz;
float3 d = B - A;
float dn = dot(N, d);
if (abs(dn) < WS_EPS) return OutsideColor;
float3 d = bP - aP;
float dz = d.z;
float t = dot(N, P0 - A) / dn;
if (t < 0.0 || t > 1.0) return OutsideColor;
float3 hit = A + d * t;
float3 r = hit - P0;
// Parallel-ish to plane?
if (abs(dz) < EPS) return false;
// u,v in [-0.5, 0.5] if inside quad
float u = dot(r, Uinv);
float v = dot(r, Vinv);
if (abs(u) > 0.5 || abs(v) > 0.5) return OutsideColor;
// Intersect z=0
t = -aP.z / dz;
// Segment only
if (t < 0.0 || t > 1.0) return false;
float3 hit = aP + d * t;
// Inside 1x1 centered quad?
if (abs(hit.x) > 0.5 || abs(hit.y) > 0.5) return false;
uv = hit.xy + 0.5; // [-0.5,0.5] -> [0,1]
return true;
}
// Fragment-shader version: uses proper filtering/mips via tex2D
inline float4 SampleShadowcasterPlane(float4x4 worldToLocal, sampler2D tex, float3 rayOrigin, float3 rayEnd, float4 OutsideColor)
{
float2 uv; float t;
if (RaySegmentHitsPlaneQuad(worldToLocal, rayOrigin, rayEnd, uv, t))
return tex2D(tex, uv); // full color
return OutsideColor;
}
// Anywhere (vertex/geom/compute/custom code) version: forces LOD 0
inline float4 SampleShadowcasterPlaneLOD0(float4x4 worldToLocal, sampler2D tex, float3 rayOrigin, float3 rayEnd, float4 OutsideColor)
{
float2 uv; float t;
if (RaySegmentHitsPlaneQuad(worldToLocal, rayOrigin, rayEnd, uv, t))
return tex2Dlod(tex, float4(uv, 0, 0)); // full color at mip 0
return OutsideColor;
float4 returnColor = tex2D(tex, float2(u + 0.5, v + 0.5)) * ShadowColor;
returnColor = float4(returnColor.rgb * (1 - returnColor.a), 1);
return returnColor;
}
#endif