- Qt 6.7
- Qt Quick 3D
- Qt Quick 3D Examples and Tutorials
- Qt Quick 3D - Simple Skinning Example
- Qt Quick 3D | Commercial or GPLv3

# Qt Quick 3D - Simple Skinning Example

     // Copyright (C) 2020 The Qt Company Ltd.
     // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

     #include "skingeometry.h"

     #include <qmath.h>

     struct Vertex {
         QVector3D position;
         qint32 joints[4];
         float weights[4];

         float pad;
     };

     static const int s_vertexSize = sizeof(Vertex);
     Q_STATIC_ASSERT(s_vertexSize == 48);

     SkinGeometry::SkinGeometry(QQuick3DObject *parent)
         : QQuick3DGeometry(parent)
     {
         addAttribute(QQuick3DGeometry::Attribute::PositionSemantic, 0,
                      QQuick3DGeometry::Attribute::ComponentType::F32Type);
         addAttribute(QQuick3DGeometry::Attribute::IndexSemantic, 0,
                      QQuick3DGeometry::Attribute::ComponentType::U32Type);
         addAttribute(QQuick3DGeometry::Attribute::JointSemantic, offsetof(Vertex, joints[0]),
                      QQuick3DGeometry::Attribute::ComponentType::I32Type);
         addAttribute(QQuick3DGeometry::Attribute::WeightSemantic, offsetof(Vertex, weights[0]),
                      QQuick3DGeometry::Attribute::ComponentType::F32Type);
     }

     QList<QVector3D> SkinGeometry::positions() const
     {
         return m_positions;
     }

     QList<qint32> SkinGeometry::joints() const
     {
         return m_joints;
     }

     QList<float> SkinGeometry::weights() const
     {
         return m_weights;
     }

     QList<quint32> SkinGeometry::indexes() const
     {
         return m_indexes;
     }

     void SkinGeometry::setPositions(const QList<QVector3D> &positions)
     {
         if (positions == m_positions)
             return;
         m_positions = positions;
         emit positionsChanged();
         m_vertexDirty = true;
     }

     void SkinGeometry::setJoints(const QList<qint32> &joints)
     {
         if (joints == m_joints)
             return;
         m_joints = joints;
         emit jointsChanged();
         m_vertexDirty = true;
     }

     void SkinGeometry::setWeights(const QList<float> &weights)
     {
         if (weights == m_weights)
             return;
         m_weights = weights;
         emit weightsChanged();
         m_vertexDirty = true;
     }

     void SkinGeometry::setIndexes(const QList<quint32> &indexes)
     {
         if (indexes == m_indexes)
             return;
         m_indexes = indexes;
         emit indexesChanged();
         m_indexDirty = true;
     }

     QSSGRenderGraphObject *SkinGeometry::updateSpatialNode(QSSGRenderGraphObject *node)
     {
         if (m_vertexDirty) {
             m_vertexDirty = false;

             constexpr float maxFloat = std::numeric_limits<float>::max();
             auto boundsMin = QVector3D(maxFloat, maxFloat, maxFloat);
             auto boundsMax = QVector3D(-maxFloat, -maxFloat, -maxFloat);

             const int numVertexes = m_positions.size();
             m_vertexBuffer.resize(numVertexes * s_vertexSize);
             Vertex *vert = reinterpret_cast<Vertex *>(m_vertexBuffer.data());

             for (int i = 0; i < numVertexes; ++i) {
                 Vertex &v = vert[i];
                 v.position = m_positions[i];
                 if (m_joints.size() >= 4 * (i + 1))
                     memcpy(v.joints, m_joints.constData() + 4 * i, 4 * sizeof(qint32));
                 else
                     v.joints[0] = v.joints[1] = v.joints[2] = v.joints[3] = 0;
                 if (m_weights.size() >= 4 * (i + 1))
                     memcpy(v.weights, m_weights.constData() + 4 * i, 4 * sizeof(float));
                 else
                     v.weights[0] = v.weights[1] = v.weights[2] = v.weights[3] = 0.0f;

                 boundsMin.setX(std::min(boundsMin.x(), v.position.x()));
                 boundsMin.setY(std::min(boundsMin.y(), v.position.y()));
                 boundsMin.setZ(std::min(boundsMin.z(), v.position.z()));

                 boundsMax.setX(std::max(boundsMax.x(), v.position.x()));
                 boundsMax.setY(std::max(boundsMax.y(), v.position.y()));
                 boundsMax.setZ(std::max(boundsMax.z(), v.position.z()));
             }

             setStride(s_vertexSize);
             setVertexData(m_vertexBuffer);
             setPrimitiveType(QQuick3DGeometry::PrimitiveType::Triangles);
             setBounds(boundsMin, boundsMax);
         }

         if (m_indexDirty) {
             m_indexDirty = false;
             m_indexBuffer = QByteArray(reinterpret_cast<char *>(m_indexes.data()), m_indexes.size() * sizeof(quint32));
             setIndexData(m_indexBuffer);
         }

         node = QQuick3DGeometry::updateSpatialNode(node);
         return node;
     }