Fix divide-by-zero in BSDF computation

alipbcs · alipbcs · commit 8ecf6ef32974 · 2025-01-29T13:33:42.000-08:00
diff --git a/Source/ZetaRenderPass/Common/BSDF.hlsli b/Source/ZetaRenderPass/Common/BSDF.hlsli
@@ -421,7 +421,7 @@ namespace BSDF
     {
         float denom = mad(whdotwo, 1 / eta, whdotwi);
         denom *= denom;
-        float dwh_dwi = whdotwi / denom;
+        float dwh_dwi = denom > 0 ? whdotwi / denom : 0;
 
         return dwh_dwi;
     }
diff --git a/Source/ZetaRenderPass/Common/BSDFSampling.hlsli b/Source/ZetaRenderPass/Common/BSDFSampling.hlsli
@@ -142,7 +142,8 @@ namespace BSDF
             // to 0 and the path-tracing loop is terminated.
 
             ret.f = BSDF::DielectricBaseSpecularTr(surface, eval.Fr_g.x) * func_t;
-            ret.bsdfOverPdf = ret.f / ret.pdf;
+            // if code reached here, pdf should > 0 unless dwh_dwi = 0
+            ret.bsdfOverPdf = ret.pdf > 0 ? ret.f / ret.pdf : 0;
             ret.wi = wi_t;
             ret.lobe = BSDF::LOBE::GLOSSY_T;
         }

Original file line number	Diff line number	Diff line change
`@@ -421,7 +421,7 @@ namespace BSDF`
`421`	`421`	`{`
`422`	`422`	`float denom = mad(whdotwo, 1 / eta, whdotwi);`
`423`	`423`	`denom *= denom;`
`424`		`- float dwh_dwi = whdotwi / denom;`
	`424`	`+ float dwh_dwi = denom > 0 ? whdotwi / denom : 0;`
`425`	`425`
`426`	`426`	`return dwh_dwi;`
`427`	`427`	`}`
Original file line number	Diff line number	Diff line change
`@@ -142,7 +142,8 @@ namespace BSDF`
`142`	`142`	`// to 0 and the path-tracing loop is terminated.`
`143`	`143`
`144`	`144`	`ret.f = BSDF::DielectricBaseSpecularTr(surface, eval.Fr_g.x) * func_t;`
`145`		`- ret.bsdfOverPdf = ret.f / ret.pdf;`
	`145`	`+ // if code reached here, pdf should > 0 unless dwh_dwi = 0`
	`146`	`+ ret.bsdfOverPdf = ret.pdf > 0 ? ret.f / ret.pdf : 0;`
`146`	`147`	`ret.wi = wi_t;`
`147`	`148`	`ret.lobe = BSDF::LOBE::GLOSSY_T;`
`148`	`149`	`}`