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Fix glTF CUBICSPLINE animation sampling #2818

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Fix glTF CUBICSPLINE animation sampling #2818

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db19e7d
Fix glTF cubic spline animation sampling
ittaigolde May 26, 2026
66aca87
Validate cubic spline animation outputs
ittaigolde May 27, 2026
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43 changes: 43 additions & 0 deletions jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/GltfLoader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@
import java.nio.ByteBuffer;
import java.nio.FloatBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Base64;
import java.util.HashMap;
import java.util.LinkedList;
Expand Down Expand Up @@ -1135,6 +1136,7 @@ public void readAnimation(int animationIndex) throws IOException {
assertNotNull(dataIndex, "No output accessor Provided for animation sampler");

String interpolation = getAsString(sampler, "interpolation");
boolean cubicSpline = "CUBICSPLINE".equals(interpolation);
if (interpolation == null || !interpolation.equals("LINEAR")) {
// JME anim system only supports Linear interpolation (will be possible with monkanim though)
// TODO rework this once monkanim is core,
Expand All @@ -1153,18 +1155,30 @@ public void readAnimation(int animationIndex) throws IOException {
if (targetPath.equals("translation")) {
trackData.timeArrays.add(new TrackData.TimeData(times, TrackData.Type.Translation));
Vector3f[] translations = readAccessorData(dataIndex, vector3fArrayPopulator);
if (cubicSpline) {
translations = getCubicSplineValues(translations);
}
trackData.translations = translations;
} else if (targetPath.equals("scale")) {
trackData.timeArrays.add(new TrackData.TimeData(times, TrackData.Type.Scale));
Vector3f[] scales = readAccessorData(dataIndex, vector3fArrayPopulator);
if (cubicSpline) {
scales = getCubicSplineValues(scales);
}
trackData.scales = scales;
} else if (targetPath.equals("rotation")) {
trackData.timeArrays.add(new TrackData.TimeData(times, TrackData.Type.Rotation));
Quaternion[] rotations = readAccessorData(dataIndex, quaternionArrayPopulator);
if (cubicSpline) {
rotations = getCubicSplineValues(rotations);
}
trackData.rotations = rotations;
} else {
trackData.timeArrays.add(new TrackData.TimeData(times, TrackData.Type.Morph));
float[] weights = readAccessorData(dataIndex, floatArrayPopulator);
if (cubicSpline) {
weights = getCubicSplineValues(weights, times.length);
}
trackData.weights = weights;
hasMorphTrack = true;
}
Expand Down Expand Up @@ -1495,6 +1509,35 @@ private MorphTrack toMorphTrack(TrackData data, Spatial spatial) {
return new MorphTrack(g, data.times, data.weights, nbMorph);
}

private <T> T[] getCubicSplineValues(T[] data) {
if (data == null) {
throw new AssetLoadException("No output data defined for cubic spline animation sampler");
}
if (data.length % 3 != 0) {
throw new AssetLoadException("Cubic spline animation sampler output does not contain tangent/value triplets");
}
T[] values = Arrays.copyOf(data, data.length / 3);
for (int i = 0; i < values.length; i++) {
values[i] = data[i * 3 + 1];
}
return values;
}
Comment on lines +1512 to +1524
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@gemini-code-assist gemini-code-assist Bot May 26, 2026

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medium

To prevent potential NullPointerExceptions, we should add a defensive null check for the data array before accessing its length or copying it.

    private <T> T[] getCubicSplineValues(T[] data) {
        if (data == null) {
            return null;
        }
        T[] values = Arrays.copyOf(data, data.length / 3);
        for (int i = 0; i < values.length; i++) {
            values[i] = data[i * 3 + 1];
        }
        return values;
    }


private float[] getCubicSplineValues(float[] data, int timesLength) {
if (data == null) {
throw new AssetLoadException("No output data defined for cubic spline animation sampler");
}
if (timesLength <= 0 || data.length % timesLength != 0 || (data.length / timesLength) % 3 != 0) {
throw new AssetLoadException("Cubic spline animation sampler output does not match input times");
}
int valuesPerTime = data.length / timesLength / 3;
float[] values = new float[timesLength * valuesPerTime];
for (int i = 0; i < timesLength; i++) {
System.arraycopy(data, (i * 3 + 1) * valuesPerTime, values, i * valuesPerTime, valuesPerTime);
}
return values;
}
Comment on lines +1526 to +1539
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@gemini-code-assist gemini-code-assist Bot May 26, 2026

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medium

To prevent potential NullPointerExceptions and ArithmeticException (division by zero if timesLength is 0), we should add defensive checks for data and timesLength.

    private float[] getCubicSplineValues(float[] data, int timesLength) {
        if (data == null) {
            return null;
        }
        if (timesLength <= 0) {
            return new float[0];
        }
        int valuesPerTime = data.length / timesLength / 3;
        float[] values = new float[timesLength * valuesPerTime];
        for (int i = 0; i < timesLength; i++) {
            System.arraycopy(data, (i * 3 + 1) * valuesPerTime, values, i * valuesPerTime, valuesPerTime);
        }
        return values;
    }


public <T> T fetchFromCache(String name, int index, Class<T> type) {
Object[] data = dataCache.get(name);
if (data == null) {
Expand Down
11 changes: 11 additions & 0 deletions jme3-plugins/src/test/java/com/jme3/scene/plugins/gltf/GltfLoaderTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,17 @@ public void testLoadEmptyScene() {
}
}

@Test
public void testLoadCubicSplineScaleAnimation() {
try {
Spatial scene = assetManager.loadModel("gltf/cubicSplineScale.gltf");
dumpScene(scene, 0);
} catch (AssetLoadException ex) {
ex.printStackTrace();
Assertions.fail("Failed to import gltf model with cubic spline scale animation");
}
}

@Test
public void testLightsPunctualExtension() {
try {
Expand Down
77 changes: 77 additions & 0 deletions jme3-plugins/src/test/resources/gltf/cubicSplineScale.gltf
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Original file line number Diff line number Diff line change
@@ -0,0 +1,77 @@
{
"asset": {
"version": "2.0"
},
"scene": 0,
"scenes": [
{
"nodes": [
0
]
}
],
"nodes": [
{
"name": "AnimatedNode"
}
],
"animations": [
{
"name": "CubicSplineScale",
"channels": [
{
"sampler": 0,
"target": {
"node": 0,
"path": "scale"
}
}
],
"samplers": [
{
"input": 0,
"interpolation": "CUBICSPLINE",
"output": 1
}
]
}
],
"buffers": [
{
"uri": "data:application/octet-stream;base64,AAAAAAAAgD8AAABAAABAQAAAgEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAPwAAgD8AAAAAAACAPwAAgD8AAAAAAACAPwAAgD8AAAAAAAAAQAAAAEAAAAAAAAAAQAAAAEAAAAAAAAAAQAAAAEAAAAAAAABAQAAAQEAAAAAAAABAQAAAQEAAAAAAAABAQAAAQEAAAAAAAACAQAAAgEAAAAAAAACAQAAAgEAAAAAAAACAQAAAgEA=",
"byteLength": 200
}
],
"bufferViews": [
{
"buffer": 0,
"byteOffset": 0,
"byteLength": 20
},
{
"buffer": 0,
"byteOffset": 20,
"byteLength": 180
}
],
"accessors": [
{
"bufferView": 0,
"componentType": 5126,
"count": 5,
"type": "SCALAR",
"min": [
0
],
"max": [
4
]
},
{
"bufferView": 1,
"componentType": 5126,
"count": 15,
"type": "VEC3"
}
]
}
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