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Add SampleGlobalSDFGradient to get normal vector of Global SDF

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This commit is contained in:
Wojciech Figat
2022-03-25 12:53:30 +01:00
parent 1271a337c5
commit 6c4e61a924
3 changed files with 34 additions and 2 deletions
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BIN
Content/Shaders/GlobalSignDistanceField.flax (Stored with Git LFS)
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31
Source/Shaders/GlobalSignDistanceField.hlsl
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@@ -76,6 +76,37 @@ float SampleGlobalSDF(const GlobalSDFData data, Texture3D<float> tex[4], float3
return distance;
}
// Samples the Global SDF and returns the gradient vector (derivative) at the given world location. Normalize it to get normal vector.
float3 SampleGlobalSDFGradient(const GlobalSDFData data, Texture3D<float> tex[4], float3 worldPosition, uint minCascade = 0)
{
float3 gradient = float3(0, 0.00001f, 0);
float distance = data.CascadePosDistance[3].w * 2.0f;
if (distance <= 0.0f)
return gradient;
UNROLL
for (uint cascade = minCascade; cascade < 4; cascade++)
{
float4 cascadePosDistance = data.CascadePosDistance[cascade];
float cascadeMaxDistance = cascadePosDistance.w * 2;
float3 posInCascade = worldPosition - cascadePosDistance.xyz;
float3 cascadeUV = posInCascade / cascadeMaxDistance + 0.5f;
float cascadeDistance = tex[cascade].SampleLevel(SamplerLinearClamp, cascadeUV, 0);
if (cascadeDistance < 0.9f && !any(cascadeUV < 0) && !any(cascadeUV > 1))
{
float texelOffset = 0.5f / data.Resolution;
float xp = tex[cascade].SampleLevel(SamplerLinearClamp, float3(cascadeUV.x + texelOffset, cascadeUV.y, cascadeUV.z), 0).x;
float xn = tex[cascade].SampleLevel(SamplerLinearClamp, float3(cascadeUV.x - texelOffset, cascadeUV.y, cascadeUV.z), 0).x;
float yp = tex[cascade].SampleLevel(SamplerLinearClamp, float3(cascadeUV.x, cascadeUV.y + texelOffset, cascadeUV.z), 0).x;
float yn = tex[cascade].SampleLevel(SamplerLinearClamp, float3(cascadeUV.x, cascadeUV.y - texelOffset, cascadeUV.z), 0).x;
float zp = tex[cascade].SampleLevel(SamplerLinearClamp, float3(cascadeUV.x, cascadeUV.y, cascadeUV.z + texelOffset), 0).x;
float zn = tex[cascade].SampleLevel(SamplerLinearClamp, float3(cascadeUV.x, cascadeUV.y, cascadeUV.z - texelOffset), 0).x;
gradient = float3(xp - xn, yp - yn, zp - zn) * cascadeMaxDistance;
break;
}
}
return gradient;
}
// Ray traces the Global SDF.
GlobalSDFHit RayTraceGlobalSDF(const GlobalSDFData data, Texture3D<float> tex[4], Texture3D<float> mips[4], const GlobalSDFTrace trace, uint minCascade = 0)
{

1
Source/Shaders/GlobalSignDistanceField.shader
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@@ -210,6 +210,7 @@ float4 PS_Debug(Quad_VS2PS input) : SV_Target
float3 color = saturate(hit.StepsCount / 80.0f).xxx;
if (!hit.IsHit())
color.rg *= 0.4f;
//else color.rgb = normalize(SampleGlobalSDFGradient(GlobalSDF, GlobalSDFTex, hit.GetHitPosition(trace)));
return float4(color, 1);
}