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[rmodels] Fix glTF skinning when joints have non-joint parent nodes #5876

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Merged
raysan5 merged 2 commits into from
May 29, 2026
Merged

[rmodels] Fix glTF skinning when joints have non-joint parent nodes #5876

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ca4dcd7
[rmodels] Fix glTF skinning when joints have non-joint parent nodes
cseelhoff May 20, 2026
b0f6ecb
Resolve review: NULL-check joint offset allocation, fail fast
cseelhoff May 29, 2026
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78 changes: 49 additions & 29 deletions src/rmodels.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5375,16 +5375,18 @@ static BoneInfo *LoadBoneInfoGLTF(cgltf_skin skin, int *boneCount)
cgltf_node node = *skin.joints[i];
if (node.name != NULL) strncpy(bones[i].name, node.name, sizeof(bones[i].name) - 1);

// Find parent bone index
// Find parent bone index by walking up the node tree past any
// non-joint ancestors (intermediate transform nodes used by some
// DCC exporters), until we hit a node that is also in skin.joints.
int parentIndex = -1;

for (unsigned int j = 0; j < skin.joints_count; j++)
cgltf_node *ancestor = node.parent;
while (ancestor != NULL && parentIndex == -1)
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{
if (skin.joints[j] == node.parent)
for (unsigned int j = 0; j < skin.joints_count; j++)
{
parentIndex = (int)j;
break;
if (skin.joints[j] == ancestor) { parentIndex = (int)j; break; }
}
if (parentIndex == -1) ancestor = ancestor->parent;
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}

bones[i].parent = parentIndex;
Expand Down Expand Up @@ -6518,17 +6520,33 @@ static ModelAnimation *LoadModelAnimationsGLTF(const char *fileName, int *animCo
*animCount = (int)data->animations_count;
animations = (ModelAnimation *)RL_CALLOC(data->animations_count, sizeof(ModelAnimation));

Transform worldTransform = { 0 };
cgltf_float cgltf_worldTransform[16] = { 0 };
cgltf_node *node = skin.joints[0];
cgltf_node_transform_world(node->parent, cgltf_worldTransform);
Matrix worldMatrix = {
cgltf_worldTransform[0], cgltf_worldTransform[4], cgltf_worldTransform[8], cgltf_worldTransform[12],
cgltf_worldTransform[1], cgltf_worldTransform[5], cgltf_worldTransform[9], cgltf_worldTransform[13],
cgltf_worldTransform[2], cgltf_worldTransform[6], cgltf_worldTransform[10], cgltf_worldTransform[14],
cgltf_worldTransform[3], cgltf_worldTransform[7], cgltf_worldTransform[11], cgltf_worldTransform[15]
};
MatrixDecompose(worldMatrix, &worldTransform.translation, &worldTransform.rotation, &worldTransform.scale);
// Precompute, per joint, the static transform contributed by any
// intermediate non-joint nodes between the joint and its nearest
// joint ancestor. This handles exporters (e.g. wow.export) that
// store bone offsets on dummy parent nodes rather than on the
// joints themselves. Depends only on the skin, not the animation.
int jointCount = (int)skin.joints_count;
Matrix *extOffset = (Matrix *)RL_MALLOC(jointCount*sizeof(Matrix));
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for (int k = 0; k < jointCount; k++)
{
extOffset[k] = MatrixIdentity();
cgltf_node *n = skin.joints[k]->parent;
while (n != NULL)
{
bool isJoint = false;
for (int jj = 0; jj < jointCount; jj++)
{
if (skin.joints[jj] == n) { isJoint = true; break; }

@kimkulling kimkulling May 22, 2026

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Formatting

}
if (isJoint) break;
Matrix nm = MatrixMultiply(MatrixMultiply(

@kimkulling kimkulling May 22, 2026

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Formatting or try to write this more readable.

MatrixScale(n->scale[0], n->scale[1], n->scale[2]),
QuaternionToMatrix((Quaternion){ n->rotation[0], n->rotation[1], n->rotation[2], n->rotation[3] })),
MatrixTranslate(n->translation[0], n->translation[1], n->translation[2]));
extOffset[k] = MatrixMultiply(extOffset[k], nm);
n = n->parent;
}
}

for (unsigned int a = 0; a < data->animations_count; a++)
{
Expand Down Expand Up @@ -6637,27 +6655,29 @@ static ModelAnimation *LoadModelAnimationsGLTF(const char *fileName, int *animCo
}
}

animations[a].keyframePoses[j][k] = (Transform){
.translation = translation,
.rotation = rotation,
.scale = scale
};
// Compose joint local TRS, then prepend the static
// intermediate non-joint offsets so the final TRS is
// expressed relative to the joint's skeleton parent.
Matrix S = MatrixScale(scale.x, scale.y, scale.z);
Matrix R = QuaternionToMatrix(rotation);
Matrix T = MatrixTranslate(translation.x, translation.y, translation.z);
Matrix jointLocal = MatrixMultiply(MatrixMultiply(S, R), T);
Matrix combined = MatrixMultiply(jointLocal, extOffset[k]);

Transform tr;
MatrixDecompose(combined, &tr.translation, &tr.rotation, &tr.scale);
animations[a].keyframePoses[j][k] = tr;
}

Transform *root = &animations[a].keyframePoses[j][0];
root->rotation = QuaternionMultiply(worldTransform.rotation, root->rotation);
root->scale = Vector3Multiply(root->scale, worldTransform.scale);
root->translation = Vector3Multiply(root->translation, worldTransform.scale);
root->translation = Vector3RotateByQuaternion(root->translation, worldTransform.rotation);
root->translation = Vector3Add(root->translation, worldTransform.translation);

BuildPoseFromParentJoints(bones, animations[a].boneCount, animations[a].keyframePoses[j]);
}

TRACELOG(LOG_INFO, "MODEL: [%s] Loaded animation: %s | Frames: %d | Duration: %fs", fileName, (animData.name != NULL)? animData.name : "NULL", animations[a].keyframeCount, animDuration);
RL_FREE(boneChannels);
RL_FREE(bones);
}

RL_FREE(extOffset);
}

if (data->skins_count > 1)
Expand Down
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