From 6fe4684102e3b2a58a730ee92d2692f7d0c0191f Mon Sep 17 00:00:00 2001
From: Matt Larsen <larsen30@llnl.gov>
Date: Thu, 23 Apr 2020 12:56:46 -0700
Subject: [PATCH] add normalization bypass for nodal scalars

---
 .../raytracing/TriangleIntersector.cxx        | 28 ++++++++++++++-----
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/vtkm/rendering/raytracing/TriangleIntersector.cxx b/vtkm/rendering/raytracing/TriangleIntersector.cxx
index 56cc42a5e..e85cef0a7 100644
--- a/vtkm/rendering/raytracing/TriangleIntersector.cxx
+++ b/vtkm/rendering/raytracing/TriangleIntersector.cxx
@@ -307,18 +307,30 @@ public:
   private:
     Precision MinScalar;
     Precision invDeltaScalar;
+    bool Normalize;
 
   public:
     VTKM_CONT
     NodalScalar(const vtkm::Float32& minScalar, const vtkm::Float32& maxScalar)
       : MinScalar(minScalar)
     {
-      //Make sure the we don't divide by zero on
-      //something like an iso-surface
-      if (maxScalar - MinScalar != 0.f)
-        invDeltaScalar = 1.f / (maxScalar - MinScalar);
+      Normalize = true;
+      if (minScalar > maxScalar)
+      {
+        // support the scalar renderer
+        Normalize = false;
+        MinScalar = 0;
+        invDeltaScalar = 1;
+      }
       else
-        invDeltaScalar = 1.f / minScalar;
+      {
+        //Make sure the we don't divide by zero on
+        //something like an iso-surface
+        if (maxScalar - MinScalar != 0.f)
+          invDeltaScalar = 1.f / (maxScalar - MinScalar);
+        else
+          invDeltaScalar = 1.f / minScalar;
+      }
     }
 
     typedef void ControlSignature(FieldIn, FieldOut, WholeArrayIn, WholeArrayIn);
@@ -338,8 +350,10 @@ public:
       //Todo: one normalization
       scalar = Precision(scalars.Get(indices[0]));
 
-      //normalize
-      scalar = (scalar - MinScalar) * invDeltaScalar;
+      if (Normalize)
+      {
+        scalar = (scalar - MinScalar) * invDeltaScalar;
+      }
     }
   }; //class LerpScalar