MDL_renderer: Fix nullptr access when using unsupported MDL volume.sc…

…attering expressions.

The renderer handles only direct anisotropic_vdf() at this time, not mixers or modifiers or the new fog_vdf() added in MDL 1.8.
Initialize PRD flags for primary rays to use epsilon == 0.0f.
Changed readData() to use file tellg() and read() instead of the slow std::istreambuf_iterator method.
Moved assimp includes from Application.h to Assimp.cpp.
Cast vertex attributes to const pointers inside hit.cu.
Added fabsf() overloads for float2/3/4 to vector_math.h.
Put OptiX validation mode behind USE_DEBUG_EXCEPTIONS define.
Removed duplicate "the" from comments.

apps/MDL_renderer/dp/math/Matmnt.h

@@ -353,7 +353,7 @@ namespace dp
      *  \param m1 A constant reference to the second matrix to compare.
      *  \return \c true, if \a m0 and \a m1 are equal, otherwise \c false.
      *  \remarks Two matrices are considered to be equal, if each element of \a m0 differs less than
-     *  the type dependent epsilon from the the corresponding element of \a m1. */
+     *  the type dependent epsilon from the corresponding element of \a m1. */
     template<unsigned int m, unsigned int n, typename T>
       bool operator==( const Matmnt<m,n,T> & m0, const Matmnt<m,n,T> & m1 );
 

apps/MDL_renderer/inc/Application.h

@@ -63,13 +63,6 @@
 // This include gl.h and needs to be done after glew.h
 #include <GLFW/glfw3.h>
 
-// assimp include files.
-#include <assimp/Importer.hpp>
-#include <assimp/postprocess.h>
-#include <assimp/scene.h>
-#include <assimp/DefaultLogger.hpp>
-#include <assimp/LogStream.hpp>
-
 #include <map>
 #include <memory>
 #include <string>

apps/MDL_renderer/shaders/hit.cu

@@ -72,7 +72,7 @@ typedef mi::neuraylib::Shading_state_material Mdl_state;
 
 extern "C" __constant__ SystemData sysData;
 
-// This shader handles every supported feature of the the renderer.
+// This shader handles every supported feature of the renderer.
 extern "C" __global__ void __closesthit__radiance()
 {
   // Get the current rtPayload pointer from the unsigned int payload registers p0 and p1.
@@ -106,7 +106,7 @@ extern "C" __global__ void __closesthit__radiance()
   const uint3* indices = reinterpret_cast<uint3*>(theData.indices);
   const uint3  tri     = indices[thePrimitiveIndex];
 
-  const TriangleAttributes* attributes = reinterpret_cast<TriangleAttributes*>(theData.attributes);
+  const TriangleAttributes* attributes = reinterpret_cast<const TriangleAttributes*>(theData.attributes);
 
   const TriangleAttributes& attr0 = attributes[tri.x];
   const TriangleAttributes& attr1 = attributes[tri.y];
@@ -553,7 +553,7 @@ extern "C" __global__ void __closesthit__radiance_no_emission()
   const uint3* indices = reinterpret_cast<uint3*>(theData.indices);
   const uint3  tri     = indices[thePrimitiveIndex];
 
-  const TriangleAttributes* attributes = reinterpret_cast<TriangleAttributes*>(theData.attributes);
+  const TriangleAttributes* attributes = reinterpret_cast<const TriangleAttributes*>(theData.attributes);
 
   const TriangleAttributes& attr0 = attributes[tri.x];
   const TriangleAttributes& attr1 = attributes[tri.y];
@@ -843,7 +843,7 @@ extern "C" __global__ void __anyhit__radiance_cutout()
   const uint3* indices = reinterpret_cast<uint3*>(theData.indices);
   const uint3  tri     = indices[thePrimitiveIndex];
 
-  const TriangleAttributes* attributes = reinterpret_cast<TriangleAttributes*>(theData.attributes);
+  const TriangleAttributes* attributes = reinterpret_cast<const TriangleAttributes*>(theData.attributes);
 
   const TriangleAttributes& attr0 = attributes[tri.x];
   const TriangleAttributes& attr1 = attributes[tri.y];
@@ -864,7 +864,7 @@ extern "C" __global__ void __anyhit__radiance_cutout()
   float3 tg = attr0.tangent * alpha + attr1.tangent * theBarycentrics.x + attr2.tangent * theBarycentrics.y;
 
   // Transform attributes into internal space == world space.
-  po = transformPoint(objectToWorld,  po);
+  po = transformPoint(objectToWorld, po);
   ns = normalize(transformNormal(worldToObject, ns));
   ng = normalize(transformNormal(worldToObject, ng));
   // This is actually the geometry tangent which for the runtime generated geometry objects
@@ -966,7 +966,7 @@ extern "C" __global__ void __anyhit__shadow_cutout() // For the radiance ray typ
   const uint3  tri     = indices[thePrimitiveIndex];
 
   // Cast the CUdeviceptr to the actual format for Triangles geometry.
-  const TriangleAttributes* attributes = reinterpret_cast<TriangleAttributes*>(theData.attributes);
+  const TriangleAttributes* attributes = reinterpret_cast<const TriangleAttributes*>(theData.attributes);
 
   const TriangleAttributes& attr0 = attributes[tri.x];
   const TriangleAttributes& attr1 = attributes[tri.y];
@@ -1311,7 +1311,7 @@ extern "C" __global__ void __closesthit__curves()
   const unsigned int* indices = reinterpret_cast<unsigned int*>(theData.indices);
   const unsigned int  index   = indices[thePrimitiveIndex];
 
-  const CurveAttributes* attributes = reinterpret_cast<CurveAttributes*>(theData.attributes);
+  const CurveAttributes* attributes = reinterpret_cast<const CurveAttributes*>(theData.attributes);
 
   float4 spline[4];
 

apps/MDL_renderer/shaders/raygeneration.cu

@@ -108,6 +108,7 @@ __forceinline__ __device__ float3 integrator(PerRayData& prd)
   prd.radiance   = make_float3(0.0f);
   prd.pdf        = 0.0f;
   prd.throughput = make_float3(1.0f);
+  prd.flags      = 0;
   prd.sigma_t    = make_float3(0.0f); // Extinction coefficient: sigma_a + sigma_s.
   prd.walk       = 0;                 // Number of random walk steps taken through volume scattering. 
   prd.eventType  = mi::neuraylib::BSDF_EVENT_ABSORB; // Initialize for exit. (Otherwise miss programs do not work.)