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fix: bad gltf math on inverse bind matrix in export

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This commit is contained in:
Jan Laupetin
2025-08-09 13:36:41 +01:00
parent 0cc47ce12c
commit 98fe3ed6f7
1 changed files with 81 additions and 12 deletions
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93
src/ObjWriting/XModel/Gltf/GltfWriter.cpp
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@@ -25,6 +25,66 @@ namespace
float uv[2];
};
void LhcToRhcCoordinates(float (&coords)[3])
{
const float two[3]{coords[0], coords[1], coords[2]};
coords[0] = two[0];
coords[1] = two[2];
coords[2] = -two[1];
}
void LhcToRhcCoordinates(std::array<float, 3>& coords)
{
float two[3]{coords[0], coords[1], coords[2]};
LhcToRhcCoordinates(two);
coords[0] = two[0];
coords[1] = two[1];
coords[2] = two[2];
}
void LhcToRhcQuaternion(float (&quat)[4])
{
const float two[4]{quat[0], quat[1], quat[2], quat[3]};
quat[0] = two[0];
quat[1] = two[2];
quat[2] = -two[1];
quat[3] = two[3];
}
void LhcToRhcQuaternion(std::array<float, 4>& quat)
{
float two[4]{quat[0], quat[1], quat[2], quat[3]};
LhcToRhcQuaternion(two);
quat[0] = two[0];
quat[1] = two[1];
quat[2] = two[2];
quat[3] = two[3];
}
void LhcToRhcIndices(unsigned short* indices)
{
const unsigned short two[3]{indices[0], indices[1], indices[2]};
indices[0] = two[2];
indices[1] = two[1];
indices[2] = two[0];
}
void LhcToRhcMatrix(Eigen::Matrix4f& matrix)
{
const Eigen::Matrix4f convertMatrix({
{1.0, 0.0, 0.0, 0.0},
{0.0, 0.0, 1.0, 0.0},
{0.0, -1.0, 0.0, 0.0},
{0.0, 0.0, 0.0, 1.0}
});
const auto result = convertMatrix * matrix;
matrix = result;
}
class GltfWriterImpl final : public gltf::Writer
{
public:
@@ -256,8 +316,12 @@ namespace
rotation.normalize();
boneNode.name = bone.name;
boneNode.translation = std::to_array({translation.x(), translation.z(), -translation.y()});
boneNode.rotation = std::to_array({rotation.x(), rotation.z(), -rotation.y(), rotation.w()});
boneNode.translation = std::to_array({translation.x(), translation.y(), translation.z()});
LhcToRhcCoordinates(*boneNode.translation);
boneNode.rotation = std::to_array({rotation.x(), rotation.y(), rotation.z(), rotation.w()});
LhcToRhcQuaternion(*boneNode.rotation);
std::vector<unsigned> children;
for (auto maybeChildIndex = 0u; maybeChildIndex < boneCount; maybeChildIndex++)
@@ -471,8 +535,9 @@ namespace
auto* vertex = reinterpret_cast<GltfVertex*>(&bufferData[currentBufferOffset]);
vertex->coordinates[0] = commonVertex.coordinates[0];
vertex->coordinates[1] = commonVertex.coordinates[2];
vertex->coordinates[2] = -commonVertex.coordinates[1];
vertex->coordinates[1] = commonVertex.coordinates[1];
vertex->coordinates[2] = commonVertex.coordinates[2];
LhcToRhcCoordinates(vertex->coordinates);
minPosition[0] = std::min(minPosition[0], vertex->coordinates[0]);
minPosition[1] = std::min(minPosition[1], vertex->coordinates[1]);
@@ -482,8 +547,9 @@ namespace
maxPosition[2] = std::max(maxPosition[2], vertex->coordinates[2]);
vertex->normal[0] = commonVertex.normal[0];
vertex->normal[1] = commonVertex.normal[2];
vertex->normal[2] = -commonVertex.normal[1];
vertex->normal[1] = commonVertex.normal[1];
vertex->normal[2] = commonVertex.normal[2];
LhcToRhcCoordinates(vertex->normal);
vertex->uv[0] = commonVertex.uv[0];
vertex->uv[1] = commonVertex.uv[1];
@@ -531,11 +597,13 @@ namespace
auto* inverseBindMatrixData = reinterpret_cast<float*>(&bufferData[currentBufferOffset]);
for (const auto& bone : xmodel.m_bones)
{
const auto translation = Eigen::Translation3f(bone.globalOffset[0], bone.globalOffset[2], -bone.globalOffset[1]);
const auto rotation = Eigen::Quaternionf(bone.globalRotation.w, bone.globalRotation.x, bone.globalRotation.z, -bone.globalRotation.y);
const auto translation = Eigen::Translation3f(bone.globalOffset[0], bone.globalOffset[1], bone.globalOffset[2]);
const auto rotation = Eigen::Quaternionf(bone.globalRotation.w, bone.globalRotation.x, bone.globalRotation.y, bone.globalRotation.z);
const auto bindMatrixTransform = translation * rotation;
auto bindMatrix = bindMatrixTransform.matrix();
const auto bindMatrix = (translation * rotation);
const auto inverseBindMatrix = bindMatrix.matrix().inverse();
LhcToRhcMatrix(bindMatrix);
const auto inverseBindMatrix = bindMatrix.inverse();
// GLTF matrix is column major
inverseBindMatrixData[0] = inverseBindMatrix(0, 0);
@@ -565,9 +633,10 @@ namespace
for (const auto& face : object.m_faces)
{
auto* faceIndices = reinterpret_cast<unsigned short*>(&bufferData[currentBufferOffset]);
faceIndices[0] = static_cast<unsigned short>(face.vertexIndex[2]);
faceIndices[0] = static_cast<unsigned short>(face.vertexIndex[0]);
faceIndices[1] = static_cast<unsigned short>(face.vertexIndex[1]);
faceIndices[2] = static_cast<unsigned short>(face.vertexIndex[0]);
faceIndices[2] = static_cast<unsigned short>(face.vertexIndex[2]);
LhcToRhcIndices(faceIndices);
currentBufferOffset += sizeof(unsigned short) * 3u;
}