Fix AMR block sampling at the exact upper bound, closes #26

Author: johguenther

CHANGELOG.md

@@ -4,6 +4,7 @@ Version History
 ### Open VKL 2.0.2
 
 -   Fix used element size in copyDeviceBufferToHost
+-   Fix corner case when sampling AMR blocks at exactly the upper bound
 -   Minimum CMake version is now v3.10
 -   Minimum ISPC version is now v1.30.0
 -   Superbuild updates to latest versions of dependencies

openvkl/devices/cpu/volume/amr/AMRData.cpp

@@ -25,13 +25,15 @@ namespace openvkl {
         this->cellWidth = info.cellWidth;
         this->value     = *ispc(data);
         this->dims      = this->box.size() + vec3i(1);
-        this->f_dims    = vec3f(this->dims);
+        // make it an ULP smaller such that floor(relBrickPos*f_dims) yields
+        // correct index even for relBrickPos=1.0f
+        this->f_dims    = nextafter(this->dims, -1);
 
         this->worldBounds =
             box3f(vec3f(this->box.lower) * this->cellWidth,
                   vec3f(this->box.upper + vec3i(1)) * this->cellWidth);
         this->gridToWorldScale = 1.f / this->cellWidth;
-        this->worldToGridScale = rcp(this->worldBounds.size());
+        this->worldToGridScale = 1.f / this->worldBounds.size();
       }
 
       /*! this structure defines only the format of the INPUT of amr

openvkl/devices/cpu/volume/amr/AMRVolume.ih

@@ -11,5 +11,5 @@ inline void AMRVolume_transformObjectToLocal(
     varying vec3f &localCoordinates)
 {
   localCoordinates =
-      rcp(volume->gridSpacing) * (objectCoordinates - volume->gridOrigin);
+      (1.0f/volume->gridSpacing) * (objectCoordinates - volume->gridOrigin);
 }

testing/apps/tests/amr_volume_sampling.cpp

@@ -38,6 +38,9 @@ void amr_sampling_at_shell_boundaries(vec3i dimensions, vec3i step = vec3i(1))
   offsets.emplace_back(114.0f);
   offsets.emplace_back(128.0f);
 
+  // sample at the exact brick bound, resulting in relBrickPos=1.0
+  offsets.emplace_back(256.0f);
+
   for (const vec3f &offset : offsets) {
     const auto offsetWithStep = offset * step;
 

testing/apps/tests/vdb_volume_dense.cpp

@@ -356,7 +356,7 @@ TEST_CASE("VDB volume dense consistency", "[volume_sampling]")
             .value_or(std::string(""));
 
     if (vdbFilename.empty()) {
-      WARN("OPENVDB_TEST_VDB_FILENAME not set; not running .vdb tests");
+      WARN("OPENVKL_TEST_VDB_FILENAME not set; not running .vdb tests");
       return;
     }