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Fix artifacts when sampling AMR volume #35

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Merged
johguenther merged 2 commits into from
Mar 25, 2026
Merged

Fix artifacts when sampling AMR volume #35

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1195b28
Code cleanup
johguenther Mar 24, 2026
621b774
Fix artifacts when sampling AMR volume, closes #34
johguenther Mar 25, 2026
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,10 @@
Version History
---------------

### Open VKL 2.0.3

- Fix artifacts when sampling AMR volume

### Open VKL 2.0.2

- Fix used element size in copyDeviceBufferToHost
Expand Down
4 changes: 1 addition & 3 deletions openvkl/devices/cpu/volume/amr/AMRData.cpp
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Expand Up @@ -25,9 +25,7 @@ namespace openvkl {
this->cellWidth = info.cellWidth;
this->value = *ispc(data);
this->dims = this->box.size() + vec3i(1);
// 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->f_dims = vec3f(this->dims);

this->worldBounds =
box3f(vec3f(this->box.lower) * this->cellWidth,
Expand Down
8 changes: 6 additions & 2 deletions openvkl/devices/cpu/volume/amr/CellRef.ispc
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Expand Up @@ -28,8 +28,10 @@ extern CellRef findCell(const AMR *uniform self,
for (uniform int i=0;any(true);i++) {
const AMRBrick *uniform brick = leaf->brickList[i];
if (brick->cellWidth >= minWidth) {
const vec3f relBrickPos
vec3f relBrickPosUnclamped
= (worldSpacePos - brick->bounds.lower) * brick->bounds_scale;
// clamp to 1ULP-less-1 for f_bc stay in valid index range
const vec3f relBrickPos = min(relBrickPosUnclamped, make_vec3f(0x1.fffffep-1f));
// brick coords: integer cell coordinates inside brick
// OPT: the same calculations as below, just in
// floats. this works as long as all values we calculate
Expand Down Expand Up @@ -75,8 +77,10 @@ extern CellRef findLeafCell(const AMR *uniform self,
if (isLeaf(node)) {
const AMRLeaf *uniform leaf = &self->leaf[getOfs(node)];
const AMRBrick *uniform brick = leaf->brickList[0];
const vec3f relBrickPos
const vec3f relBrickPosUnclamped
= (worldSpacePos - brick->bounds.lower) * brick->bounds_scale;
// clamp to 1ULP-less-1 for f_bc stay in valid index range
const vec3f relBrickPos = min(relBrickPosUnclamped, make_vec3f(0x1.fffffep-1f));
// brick coords: integer cell coordinates inside brick
// OPT: the same calculations as below, just in
// floats. this works as long as all values we calculate
Expand Down
48 changes: 11 additions & 37 deletions openvkl/devices/cpu/volume/amr/DualCell.ih
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Expand Up @@ -40,20 +40,6 @@ inline vec3f dualCellLerpWeightsForLevel(const vec3f &P, const float cellWidth)
return (xfmed - f_idx);
}

inline void initDualCell(DualCell &D,
const vec3f &P,
const uniform AMRLevel &level)
{
const float cellWidth = level.cellWidth;
const float halfCellWidth = 0.5f*cellWidth;
const float rcpCellWidth = rcp(cellWidth);
const vec3f xfmed = (P-halfCellWidth)*rcpCellWidth;
const vec3f f_idx = floor(xfmed);
D.cellID.pos = f_idx * cellWidth + halfCellWidth;
D.cellID.width = cellWidth;
D.weights = xfmed - f_idx;
}

inline void initDualCell(DualCell &D, const vec3f &P, const float cellWidth)
{
const float halfCellWidth = cellWidth * 0.5f;
Expand All @@ -65,6 +51,13 @@ inline void initDualCell(DualCell &D, const vec3f &P, const float cellWidth)
D.weights = xfmed - f_idx;
}

inline void initDualCell(DualCell &D,
const vec3f &P,
const uniform AMRLevel &level)
{
initDualCell(D, P, level.cellWidth);
}

inline bool allCornersAreLeaves(const DualCell &D)
{
return
Expand All @@ -91,9 +84,8 @@ inline bool allCornersArePresent(const DualCell &D)
(D.actualWidth[7] == D.cellID.width);
}

inline float lerp(const DualCell &D)
inline float lerpWithExplicitWeights(const DualCell &D, const vec3f &w)
{
const vec3f &w = D.weights;
const float f000 = D.value[C000];
const float f001 = D.value[C001];
const float f010 = D.value[C010];
Expand All @@ -115,27 +107,9 @@ inline float lerp(const DualCell &D)
return f;
}

inline float lerpWithExplicitWeights(const DualCell &D, const vec3f &w)
inline float lerp(const DualCell &D)
{
const float f000 = D.value[C000];
const float f001 = D.value[C001];
const float f010 = D.value[C010];
const float f011 = D.value[C011];
const float f100 = D.value[C100];
const float f101 = D.value[C101];
const float f110 = D.value[C110];
const float f111 = D.value[C111];

const float f00 = (1.f-w.x)*f000 + w.x*f001;
const float f01 = (1.f-w.x)*f010 + w.x*f011;
const float f10 = (1.f-w.x)*f100 + w.x*f101;
const float f11 = (1.f-w.x)*f110 + w.x*f111;

const float f0 = (1.f-w.y)*f00+w.y*f01;
const float f1 = (1.f-w.y)*f10+w.y*f11;

const float f = (1.f-w.z)*f0+w.z*f1;
return f;
return lerpWithExplicitWeights(D, D.weights);
}

inline float lerpAlpha(const DualCell &D)
Expand Down Expand Up @@ -174,4 +148,4 @@ extern void findDualCell(const AMR *uniform self,
corner */
extern void findMirroredDualCell(const AMR *uniform self,
const vec3i &loID,
DualCell &dual);
DualCell &dual);
5 changes: 4 additions & 1 deletion openvkl/devices/gpu/compute/amr/CellRef.h
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Expand Up @@ -55,8 +55,11 @@ namespace ispc {
if (isLeaf(node)) {
const AMRLeaf *leaf = &self->leaf[getOfs(node)];
const AMRBrick *brick = leaf->brickList[0];
const vec3f relBrickPos =
const vec3f relBrickPosUnclamped =
(worldSpacePos - brick->bounds.lower) * brick->bounds_scale;
// clamp to 1ULP-less-1 for f_bc stay in valid index range
const vec3f relBrickPos =
min(relBrickPosUnclamped, vec3f(0x1.fffffep-1f));
Comment on lines +61 to +62
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Copilot AI Mar 25, 2026

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The clamp uses a hard-to-read hex float literal (0x1.fffffep-1f) to represent the largest float < 1.0. Consider defining this as a named constant (or computing it via nextafter(1.f, 0.f)) to make the intent clearer and avoid duplicating the literal elsewhere.

Copilot uses AI. Check for mistakes.
// brick coords: integer cell coordinates inside brick
// OPT: the same calculations as below, just in
// floats. this works as long as all values we calculate
Expand Down
42 changes: 8 additions & 34 deletions openvkl/devices/gpu/compute/amr/DualCell.h
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Expand Up @@ -7,7 +7,7 @@ namespace ispc {

struct DualCellID
{
// position of LOWER-LEFT COORDINATE (ie, CENTER of lower-left cell
// position of LOWER-LEFT COORDINATE (ie, CENTER of lower-left cell)
vec3f pos;
// width of dual cell, also doubles as level indicator
float width;
Expand Down Expand Up @@ -38,10 +38,9 @@ namespace ispc {
return (xfmed - f_idx);
}

inline void initDualCell(DualCell &D, const vec3f &P, const AMRLevel &level)
inline void initDualCell(DualCell &D, const vec3f &P, const float cellWidth)
{
const float cellWidth = level.cellWidth;
const float halfCellWidth = 0.5f * cellWidth;
const float halfCellWidth = cellWidth * 0.5f;
const float rcpCellWidth = rcp(cellWidth);
const vec3f xfmed = (P - halfCellWidth) * rcpCellWidth;
const vec3f f_idx = floor(xfmed);
Expand All @@ -50,15 +49,9 @@ namespace ispc {
D.weights = xfmed - f_idx;
}

inline void initDualCell(DualCell &D, const vec3f &P, const float cellWidth)
inline void initDualCell(DualCell &D, const vec3f &P, const AMRLevel &level)
{
const float halfCellWidth = cellWidth * 0.5f;
const float rcpCellWidth = rcp(cellWidth);
const vec3f xfmed = (P - halfCellWidth) * rcpCellWidth;
const vec3f f_idx = floor(xfmed);
D.cellID.pos = f_idx * cellWidth + halfCellWidth;
D.cellID.width = cellWidth;
D.weights = xfmed - f_idx;
initDualCell(D, P, level.cellWidth);
}

inline bool allCornersAreLeaves(const DualCell &D)
Expand All @@ -79,9 +72,8 @@ namespace ispc {
(D.actualWidth[7] == D.cellID.width);
}

inline float lerp(const DualCell &D)
inline float lerpWithExplicitWeights(const DualCell &D, const vec3f &w)
{
const vec3f &w = D.weights;
const float f000 = D.value[C000];
const float f001 = D.value[C001];
const float f010 = D.value[C010];
Expand All @@ -103,27 +95,9 @@ namespace ispc {
return f;
}

inline float lerpWithExplicitWeights(const DualCell &D, const vec3f &w)
inline float lerp(const DualCell &D)
{
const float f000 = D.value[C000];
const float f001 = D.value[C001];
const float f010 = D.value[C010];
const float f011 = D.value[C011];
const float f100 = D.value[C100];
const float f101 = D.value[C101];
const float f110 = D.value[C110];
const float f111 = D.value[C111];

const float f00 = (1.f - w.x) * f000 + w.x * f001;
const float f01 = (1.f - w.x) * f010 + w.x * f011;
const float f10 = (1.f - w.x) * f100 + w.x * f101;
const float f11 = (1.f - w.x) * f110 + w.x * f111;

const float f0 = (1.f - w.y) * f00 + w.y * f01;
const float f1 = (1.f - w.y) * f10 + w.y * f11;

const float f = (1.f - w.z) * f0 + w.z * f1;
return f;
return lerpWithExplicitWeights(D, D.weights);
}

inline float lerpAlpha(const DualCell &D)
Expand Down
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