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

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

Some glTF exporters (notably wow.export, but also various other DCC pipelines) place skin joints under intermediate non-joint transform nodes that carry part of the bind-pose offset. raylib's existing LoadBoneInfoGLTF and LoadModelAnimationsGLTF only inspected a joint's immediate parent and only sampled joint-local TRS, so any transform stored on an intermediate non-joint ancestor was silently dropped, producing exploded or stretched meshes at runtime.

Two surgical changes:

LoadBoneInfoGLTF: walk the parent chain past any non-joint ancestors when looking up parentIndex, instead of comparing only against node.parent. Joints whose direct parent is a non-joint were previously treated as skeleton roots.

LoadModelAnimationsGLTF: precompute a per-joint extOffset matrix that bakes in the static TRS contribution of any intermediate non-joint nodes between the joint and its nearest joint ancestor. Apply it to each frame's joint TRS before BuildPoseFromParentJoints so the per-frame world transforms match the bind-pose world transforms (LoadGLTF already used cgltf_node_transform_world for bindPose, so this aligns the two code paths).

The replaced root-only worldTransform adjustment is a strict subset of the new per-joint extOffset machinery, so it has been removed.

Spec-compliant files (the six skeletal-skinning .glb examples shipped with raylib) render bit-identically before and after; previously broken files (e.g. wow.export's babyoctopus.gltf) now match the reference rendering from f3d, the Khronos sample viewer, and three.js.

* Resolve review: NULL-check joint offset allocation, fail fast

[rmodels] Address review feedback on glTF joint offset handling

Resolve the open review points raised on PR #5876 for the per-joint
extOffset precompute in LoadModelAnimationsGLTF.

* NULL check: validate the extOffset RL_MALLOC result before use, which
  was previously missing.

* Fail-fast handling: detect the allocation failure at its source and
  abort animation loading (log a warning, free resources, return NULL)
  instead of propagating a NULL pointer into the per-frame loop.

* Brace formatting: expand the collapsed one-line joint-match check
  (if (...) { isJoint = true; break; }) into raylib's standard Allman
  brace style.

* Readability: break the deeply nested MatrixMultiply(MatrixMultiply(...))
  into named nodeScale/nodeRotation/nodeTranslation/nodeTransform locals,
  mirroring the existing S/R/T composition later in the function.

* Spacing/line breaks: add blank lines within the precompute block to
  match the surrounding code style.
This commit is contained in:
Caleb Seelhoff
2026-05-29 12:17:04 -04:00
committed by GitHub
parent 186d3ce9fb
commit 81c7cb6527
1 changed files with 71 additions and 29 deletions
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100
src/rmodels.c
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@@ -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)
{
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;
}
bones[i].parent = parentIndex;
@@ -6515,20 +6517,58 @@ static ModelAnimation *LoadModelAnimationsGLTF(const char *fileName, int *animCo
if (data->skins_count > 0)
{
cgltf_skin skin = data->skins[0];
// 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));
if (extOffset == NULL)
{
// Allocation failed: abort animation loading at the source rather than
// propagating a NULL pointer into the per-frame transform loop below
TRACELOG(LOG_WARNING, "MODEL: [%s] Failed to allocate joint offset buffer", fileName);
cgltf_free(data);
UnloadFileData(fileData);
*animCount = 0;
return NULL;
}
*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);
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;
}
}
if (isJoint) break;
// Compose the intermediate node's local TRS (scale, then rotation, then translation)
Matrix nodeScale = MatrixScale(n->scale[0], n->scale[1], n->scale[2]);
Matrix nodeRotation = QuaternionToMatrix((Quaternion){ n->rotation[0], n->rotation[1], n->rotation[2], n->rotation[3] });
Matrix nodeTranslation = MatrixTranslate(n->translation[0], n->translation[1], n->translation[2]);
Matrix nodeTransform = MatrixMultiply(MatrixMultiply(nodeScale, nodeRotation), nodeTranslation);
extOffset[k] = MatrixMultiply(extOffset[k], nodeTransform);
n = n->parent;
}
}
for (unsigned int a = 0; a < data->animations_count; a++)
{
@@ -6637,19 +6677,19 @@ 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 *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);
Transform tr;
MatrixDecompose(combined, &tr.translation, &tr.rotation, &tr.scale);
animations[a].keyframePoses[j][k] = tr;
}
BuildPoseFromParentJoints(bones, animations[a].boneCount, animations[a].keyframePoses[j]);
}
@@ -6658,6 +6698,8 @@ static ModelAnimation *LoadModelAnimationsGLTF(const char *fileName, int *animCo
RL_FREE(boneChannels);
RL_FREE(bones);
}
RL_FREE(extOffset);
}
if (data->skins_count > 1)