Qt Quick 3D - Simple Skinning Example

 /****************************************************************************
 **
 ** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** Commercial License Usage
 ** Licensees holding valid commercial Qt licenses may use this file in
 ** accordance with the commercial license agreement provided with the
 ** Software or, alternatively, in accordance with the terms contained in
 ** a written agreement between you and The Qt Company. For licensing terms
 ** and conditions see https://www.qt.io/terms-conditions. For further
 ** information use the contact form at https://www.qt.io/contact-us.
 **
 ** BSD License Usage
 ** Alternatively, you may use this file under the terms of the BSD license
 ** as follows:
 **
 ** "Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of The Qt Company Ltd nor the names of its
 **     contributors may be used to endorse or promote products derived
 **     from this software without specific prior written permission.
 **
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #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;
 }