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#4080 Rigged mesh support #4 #4166

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May 26, 2025
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#4080 Rigged mesh support #4 #4166

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40 changes: 23 additions & 17 deletions indra/newview/gltf/llgltfloader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,14 @@ static const std::string lod_suffix[LLModel::NUM_LODS] =
"_PHYS",
};

// Premade rotation matrix, GLTF is Y-up while SL is Z-up
static const glm::mat4 coord_system_rotation(
1.f, 0.f, 0.f, 0.f,
0.f, 0.f, 1.f, 0.f,
0.f, -1.f, 0.f, 0.f,
0.f, 0.f, 0.f, 1.f
);


LLGLTFLoader::LLGLTFLoader(std::string filename,
S32 lod,
Expand Down Expand Up @@ -203,9 +211,21 @@ bool LLGLTFLoader::parseMeshes()
mesh_scale *= transformation;
transformation = mesh_scale;

// "Bind Shape Matrix" is supposed to transform the geometry of the skinned mesh
// into the coordinate space of the joints.
// In GLTF, this matrix is omitted, and it is assumed that this transform is either
// premultiplied with the mesh data, or postmultiplied to the inverse bind matrices.
//
// TODO: This appers to be missing rotation when joints rotate the model
// or inverted bind matrices are missing inherited rotation
// (based of values the 'bento shoes' mesh might be missing 90 degrees horizontaly
// prior to skinning)
pModel->mSkinInfo.mBindShapeMatrix.loadu(mesh_scale);
LL_INFOS("GLTF_DEBUG") << "Model: " << pModel->mLabel << " mBindShapeMatrix: " << pModel->mSkinInfo.mBindShapeMatrix << LL_ENDL;

if (transformation.determinant() < 0)
{ // negative scales are not supported
LL_INFOS("GLTF") << "Negative scale detected, unsupported post-normalization transform. domInstance_geometry: "
LL_INFOS("GLTF_IMPORT") << "Negative scale detected, unsupported post-normalization transform. domInstance_geometry: "
<< pModel->mLabel << LL_ENDL;
LLSD args;
args["Message"] = "NegativeScaleNormTrans";
Expand Down Expand Up @@ -280,9 +300,6 @@ bool LLGLTFLoader::populateModelFromMesh(LLModel* pModel, const LL::GLTF::Mesh&

S32 skinIdx = nodeno.mSkin;

// Pre-compute coordinate system rotation matrix (GLTF Y-up to SL Z-up)
static const glm::mat4 coord_system_rotation = glm::rotate(glm::mat4(1.0f), glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));

// Compute final combined transform matrix (hierarchy + coordinate rotation)
S32 node_index = static_cast<S32>(&nodeno - &mGLTFAsset.mNodes[0]);
glm::mat4 hierarchy_transform;
Expand Down Expand Up @@ -619,7 +636,7 @@ bool LLGLTFLoader::populateModelFromMesh(LLModel* pModel, const LL::GLTF::Mesh&
mats[materialName] = impMat;
}
else {
LL_INFOS() << "Unable to process mesh due to 16-bit index limits" << LL_ENDL;
LL_INFOS("GLTF_IMPORT") << "Unable to process mesh due to 16-bit index limits" << LL_ENDL;
LLSD args;
args["Message"] = "ParsingErrorBadElement";
mWarningsArray.append(args);
Expand All @@ -639,7 +656,7 @@ bool LLGLTFLoader::populateModelFromMesh(LLModel* pModel, const LL::GLTF::Mesh&
size_t jointCnt = gltf_skin.mJoints.size();
if (gltf_skin.mInverseBindMatrices >= 0 && jointCnt != gltf_skin.mInverseBindMatricesData.size())
{
LL_INFOS("GLTF") << "Bind matrices count mismatch joints count" << LL_ENDL;
LL_INFOS("GLTF_IMPORT") << "Bind matrices count mismatch joints count" << LL_ENDL;
LLSD args;
args["Message"] = "InvBindCountMismatch";
mWarningsArray.append(args);
Expand Down Expand Up @@ -709,14 +726,6 @@ bool LLGLTFLoader::populateModelFromMesh(LLModel* pModel, const LL::GLTF::Mesh&
}
}

// "Bind Shape Matrix" is supposed to transform the geometry of the skinned mesh
// into the coordinate space of the joints.
// In GLTF, this matrix is omitted, and it is assumed that this transform is either
// premultiplied with the mesh data, or postmultiplied to the inverse bind matrices.
LLMatrix4 bind_shape;
bind_shape.setIdentity();
skin_info.mBindShapeMatrix.loadu(bind_shape);

// Remap indices for pModel->mSkinWeights
for (auto& weights : pModel->mSkinWeights)
{
Expand All @@ -732,9 +741,6 @@ bool LLGLTFLoader::populateModelFromMesh(LLModel* pModel, const LL::GLTF::Mesh&

void LLGLTFLoader::populateJointFromSkin(const LL::GLTF::Skin& skin)
{
// Create coordinate system rotation matrix - GLTF is Y-up, SL is Z-up
glm::mat4 coord_system_rotation = glm::rotate(glm::mat4(1.0f), glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));

LL_INFOS("GLTF_DEBUG") << "populateJointFromSkin: Processing " << skin.mJoints.size() << " joints" << LL_ENDL;

for (auto joint : skin.mJoints)
Expand Down