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fix VolumeGrid isosurface indexing bug with non-uniform dimensions #378

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Merged
nmwsharp merged 2 commits into from
Dec 23, 2025
+73 −25
Merged

fix VolumeGrid isosurface indexing bug with non-uniform dimensions #378

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a19cac8
add failing test for bug
nmwsharp Dec 23, 2025
c610e52
fix volume grid isosurface indexing bug
nmwsharp Dec 23, 2025
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8 changes: 4 additions & 4 deletions src/volume_grid_scalar_quantity.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -165,8 +165,8 @@ void VolumeGridNodeScalarQuantity::createIsosurfaceProgram() {

// Extract the isosurface from the level set of the scalar field
MC::mcMesh isosurfaceMesh;
MC::marching_cube(&values.data.front(), isosurfaceLevel.get(), parent.getGridNodeDim().x, parent.getGridNodeDim().y,
parent.getGridNodeDim().z, isosurfaceMesh);
MC::marching_cube(&values.data.front(), isosurfaceLevel.get(), parent.getGridNodeDim().z, parent.getGridNodeDim().y,
parent.getGridNodeDim().x, isosurfaceMesh);

// Transform the result to be aligned with our volume's spatial layout
glm::vec3 scale = parent.gridSpacing();
Expand Down Expand Up @@ -215,8 +215,8 @@ SurfaceMesh* VolumeGridNodeScalarQuantity::registerIsosurfaceAsMesh(std::string

// extract the mesh
MC::mcMesh isosurfaceMesh;
MC::marching_cube(&values.data.front(), isosurfaceLevel.get(), parent.getGridNodeDim().x, parent.getGridNodeDim().y,
parent.getGridNodeDim().z, isosurfaceMesh);
MC::marching_cube(&values.data.front(), isosurfaceLevel.get(), parent.getGridNodeDim().z, parent.getGridNodeDim().y,
parent.getGridNodeDim().x, isosurfaceMesh);
glm::vec3 scale = parent.gridSpacing();
for (auto& p : isosurfaceMesh.vertices) {
// swizzle to account for change of coordinate/buffer ordering in the MC lib
Expand Down
90 changes: 69 additions & 21 deletions test/src/volume_grid_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@
// ============================================================

TEST_F(PolyscopeTest, ShowVolumeGrid) {
// clang-format off
uint32_t dimX = 8;
uint32_t dimY = 10;
uint32_t dimZ = 12;
Expand All @@ -19,7 +18,7 @@ TEST_F(PolyscopeTest, ShowVolumeGrid) {
polyscope::VolumeGrid* psGrid = polyscope::registerVolumeGrid("test grid", {dimX, dimY, dimZ}, bound_low, bound_high);

polyscope::show(3);

EXPECT_TRUE(polyscope::hasVolumeGrid("test grid"));
EXPECT_FALSE(polyscope::hasVolumeGrid("other grid"));
polyscope::removeAllStructures();
Expand All @@ -28,7 +27,7 @@ TEST_F(PolyscopeTest, ShowVolumeGrid) {


TEST_F(PolyscopeTest, VolumeGridBasicOptions) {

// these are node dim
uint32_t dimX = 8;
uint32_t dimY = 10;
Expand All @@ -38,8 +37,8 @@ TEST_F(PolyscopeTest, VolumeGridBasicOptions) {

polyscope::VolumeGrid* psGrid = polyscope::registerVolumeGrid("test grid", {dimX, dimY, dimZ}, bound_low, bound_high);

EXPECT_EQ(psGrid->nNodes(), dimX*dimY*dimZ);
EXPECT_EQ(psGrid->nCells(), (dimX-1)*(dimY-1)*(dimZ-1));
EXPECT_EQ(psGrid->nNodes(), dimX * dimY * dimZ);
EXPECT_EQ(psGrid->nCells(), (dimX - 1) * (dimY - 1) * (dimZ - 1));

// Material
psGrid->setMaterial("flat");
Expand All @@ -49,7 +48,7 @@ TEST_F(PolyscopeTest, VolumeGridBasicOptions) {
// Edge width
psGrid->setEdgeWidth(0.5);
polyscope::show(3);

// Grid size factor
psGrid->setCubeSizeFactor(0.5);
polyscope::show(3);
Expand All @@ -58,15 +57,14 @@ TEST_F(PolyscopeTest, VolumeGridBasicOptions) {
}

TEST_F(PolyscopeTest, VolumeGridOrthographicRendering) {
// clang-format off
uint32_t dimX = 8;
uint32_t dimY = 10;
uint32_t dimZ = 12;
glm::vec3 bound_low{-3., -3., -3.};
glm::vec3 bound_high{3., 3., 3.};

polyscope::VolumeGrid* psGrid = polyscope::registerVolumeGrid("test grid", {dimX, dimY, dimZ}, bound_low, bound_high);

// try orthographic rendering
polyscope::view::setProjectionMode(polyscope::ProjectionMode::Orthographic);
polyscope::show(3);
Expand All @@ -75,7 +73,7 @@ TEST_F(PolyscopeTest, VolumeGridOrthographicRendering) {
}

TEST_F(PolyscopeTest, VolumeGridSlicePlane) {

// these are node dim
uint32_t dimX = 8;
uint32_t dimY = 10;
Expand All @@ -87,20 +85,21 @@ TEST_F(PolyscopeTest, VolumeGridSlicePlane) {

// plain old inspecting
polyscope::SlicePlane* p = polyscope::addSceneSlicePlane();
psGrid->setCullWholeElements(true);
psGrid->setCullWholeElements(true);
polyscope::show(3);

// cull whole elements
// we don't actually support rendering like this yet, so right now this is 'handled' by automatically unsetting it internally
psGrid->setCullWholeElements(false);
// we don't actually support rendering like this yet, so right now this is 'handled' by automatically unsetting it
// internally
psGrid->setCullWholeElements(false);
polyscope::show(3);

polyscope::removeLastSceneSlicePlane();
polyscope::removeAllStructures();
}

TEST_F(PolyscopeTest, VolumeGridScalar) {

// these are node dim
uint32_t dimX = 8;
uint32_t dimY = 10;
Expand All @@ -126,19 +125,19 @@ TEST_F(PolyscopeTest, VolumeGridScalar) {
psGrid->addNodeScalarQuantity("node scalar1", nodeScalar)->setEnabled(true);
polyscope::show(3);
}

{ // node scalar from callable
// internally this bootstraps off the batch version, so we're kinda testing it too
psGrid->addNodeScalarQuantityFromCallable("node scalar2", torusSDF)->setEnabled(true);
polyscope::show(3);
}

{ // cell scalar from array
std::vector<double> cellScalar(psGrid->nCells(), 3.0f);
psGrid->addCellScalarQuantity("cell scalar1", cellScalar)->setEnabled(true);
polyscope::show(3);
}

{ // cell scalar from callable
// internally this bootstraps off the batch version, so we're kinda testing it too
psGrid->addCellScalarQuantityFromCallable("cell scalar2", torusSDF)->setEnabled(true);
Expand All @@ -149,7 +148,7 @@ TEST_F(PolyscopeTest, VolumeGridScalar) {
}

TEST_F(PolyscopeTest, VolumeGridScalarIsosurfaceAndOpts) {

// these are node dim
uint32_t dimX = 8;
uint32_t dimY = 10;
Expand Down Expand Up @@ -177,14 +176,14 @@ TEST_F(PolyscopeTest, VolumeGridScalarIsosurfaceAndOpts) {

q->setGridcubeVizEnabled(false);
polyscope::show(3);

q->setIsosurfaceVizEnabled(true); // extracts the isosurface
polyscope::show(3);

polyscope::SlicePlane* p = polyscope::addSceneSlicePlane();
polyscope::show(3);

q->setSlicePlanesAffectIsosurface(true);
q->setSlicePlanesAffectIsosurface(true);
polyscope::show(3);

q->registerIsosurfaceAsMesh();
Expand All @@ -198,3 +197,52 @@ TEST_F(PolyscopeTest, VolumeGridScalarIsosurfaceAndOpts) {
polyscope::removeLastSceneSlicePlane();
polyscope::removeAllStructures();
}

TEST_F(PolyscopeTest, VolumeGridScalarIsosurfaceIndexing) {

std::vector<std::array<int32_t, 3>> perms{{0, 1, 2}, {0, 2, 1}, {1, 0, 2}, {1, 2, 0}, {2, 0, 1}, {2, 1, 0}};

std::array<uint32_t, 3> dims = {5, 8, 20};

// these are node dim
glm::vec3 bound_low{-10., -2., -5.};
glm::vec3 bound_high{20., 3., 6.};

for (auto& perm : perms) {
uint32_t dimX = dims[perm[0]];
uint32_t dimY = dims[perm[1]];
uint32_t dimZ = dims[perm[2]];

polyscope::VolumeGrid* psGrid =
polyscope::registerVolumeGrid("test grid", {dimX, dimY, dimZ}, bound_low, bound_high);

std::vector<float> vals(dimX * dimY * dimZ, 0.f);
for (uint32_t iX = 0; iX < dimX; iX++) {
for (uint32_t iY = 0; iY < dimY; iY++) {
for (uint32_t iZ = 0; iZ < dimZ; iZ++) {
vals[iX * (dimY * dimZ) + iY * dimZ + iZ] = ((iX + iY + iZ) % 2) - 0.5; // checkerboard function
}
}
}

polyscope::VolumeGridNodeScalarQuantity* q = psGrid->addNodeScalarQuantity("node scalar", vals);
q->setIsosurfaceVizEnabled(true); // extracts the isosurface
q->registerIsosurfaceAsMesh("iso test");

// get the vertices from the is surface
polyscope::SurfaceMesh* isoTest = polyscope::getSurfaceMesh("iso test");
isoTest->vertexPositions.ensureHostBufferPopulated();
std::vector<glm::vec3> isoverts = isoTest->vertexPositions.data;

// test that all vertices are within the bounds
float EPS = 0.0001;
for (glm::vec3 p : isoverts) {
for (int i = 0; i < 3; i++) {
EXPECT_GE(p[i], bound_low[i] - EPS);
EXPECT_LT(p[i], bound_high[i] + EPS);
}
}

polyscope::removeAllStructures();
}
}