explicitly handle square root of negative value scenario. Make sure the plane pair is identified as invalid.

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/Resources/scrbound.compute

 	return mul(plane, InvProjection);
 }
 
-float4 EvalPlanePair(float2 posXY_in, float r)
+float4 EvalPlanePair(out bool validPlanes, float2 posXY_in, float r)
 {
 	// rotate by 90 degrees to avoid potential division by zero
 	bool bMustFlip = abs(posXY_in.y)<abs(posXY_in.x);
-	float D = posXY.y * sqrt(fLenSQ - r*r);
+	float diffSq = fLenSQ - r*r;
+	float D = posXY.y * sqrt(max(0.0, diffSq));
 
 	float4 res;
 	res.x = (-r*posXY.x - D) / fLenSQ;
 	// rotate back by 90 degrees
 	res = bMustFlip ? float4(res.y, -res.x, res.w, -res.z) : res;
 
+	validPlanes = diffSq>0.0;
+
-	float4 planeX = EvalPlanePair(float2(pos_view_space.x, pos_view_space.z), r);
-	float4 planeY = EvalPlanePair(float2(pos_view_space.y, pos_view_space.z), r);
+	bool validX, validY;
+	float4 planeX = EvalPlanePair(validX, float2(pos_view_space.x, pos_view_space.z), r);
+	float4 planeY = EvalPlanePair(validY, float2(pos_view_space.y, pos_view_space.z), r);
 
 
 #if USE_LEFTHAND_CAMERASPACE
 
-	bIsMinValid = bool2(planeX.z<0, planeY.z<0);
-	bIsMaxValid = bool2((-planeX.x)<0, (-planeY.x)<0);
+	bIsMinValid = bool2(planeX.z<0, planeY.z<0) && bool2(validX,validY);
+	bIsMaxValid = bool2((-planeX.x)<0, (-planeY.x)<0) && bool2(validX,validY);
 
 	// hopefully the compiler takes zeros into account
 	// should be the case since the transformation in TransformPlaneToPostSpace()

Assets/ScriptableRenderPipeline/fptl/scrbound.compute

 	return mul(plane, InvProjection);
 }
 
-float4 EvalPlanePair(float2 posXY_in, float r)
+float4 EvalPlanePair(out bool validPlanes, float2 posXY_in, float r)
 {
 	// rotate by 90 degrees to avoid potential division by zero
 	bool bMustFlip = abs(posXY_in.y)<abs(posXY_in.x);
-	float D = posXY.y * sqrt(fLenSQ - r*r);
+	float diffSq = fLenSQ - r*r;
+	float D = posXY.y * sqrt(max(0.0, diffSq));
 
 	float4 res;
 	res.x = (-r*posXY.x - D) / fLenSQ;
 	// rotate back by 90 degrees
 	res = bMustFlip ? float4(res.y, -res.x, res.w, -res.z) : res;
 
+	validPlanes = diffSq>0.0;
+
-	float4 planeX = EvalPlanePair(float2(pos_view_space.x, pos_view_space.z), r);
-	float4 planeY = EvalPlanePair(float2(pos_view_space.y, pos_view_space.z), r);
+	bool validX, validY;
+	float4 planeX = EvalPlanePair(validX, float2(pos_view_space.x, pos_view_space.z), r);
+	float4 planeY = EvalPlanePair(validY, float2(pos_view_space.y, pos_view_space.z), r);
 
 
 #if USE_LEFTHAND_CAMERASPACE
 
-	bIsMinValid = bool2(planeX.z<0, planeY.z<0);
-	bIsMaxValid = bool2((-planeX.x)<0, (-planeY.x)<0);
+	bIsMinValid = bool2(planeX.z<0, planeY.z<0) && bool2(validX,validY);
+	bIsMaxValid = bool2((-planeX.x)<0, (-planeY.x)<0) && bool2(validX,validY);
 
 	// hopefully the compiler takes zeros into account
 	// should be the case since the transformation in TransformPlaneToPostSpace()