Qt Quick 3D - Custom Morphing Animation | Qt Quick 3D 6.5.1
Description: Demonstrates writing C++ custom geometry with a morph target.

- Qt 6.5
- Qt Quick 3D
- Qt Quick 3D Examples and Tutorials
- Qt Quick 3D - Custom Morphing Animation
- Qt Quick 3D | Commercial or GPLv3

# Qt Quick 3D - Custom Morphing Animation

     // Copyright (C) 2021 The Qt Company Ltd.
     // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

     #include "morphgeometry.h"

     #include <qmath.h>
     struct Vertex {
         QVector3D position;
         QVector3D normal;

         QVector3D targetPosition;
         QVector3D targetNormal;
     };
     Q_STATIC_ASSERT((sizeof(Vertex)/16)*16 == sizeof(Vertex)); // must be  4-float aligned

     MorphGeometry::MorphGeometry(QQuick3DObject *parent)
         : QQuick3DGeometry(parent)
     {
         updateData();
     }

     void MorphGeometry::setGridSize(int gridSize)
     {
         if (m_gridSize == gridSize)
             return;

         m_gridSize = gridSize;
         emit gridSizeChanged();
         updateData();
         update();
     }

     void MorphGeometry::updateData()
     {
         clear();
         calculateGeometry();

         addAttribute(QQuick3DGeometry::Attribute::PositionSemantic, 0,
                      QQuick3DGeometry::Attribute::ComponentType::F32Type);
         addAttribute(QQuick3DGeometry::Attribute::NormalSemantic, 3 * sizeof(float),
                      QQuick3DGeometry::Attribute::ComponentType::F32Type);

         addAttribute(QQuick3DGeometry::Attribute::TargetPositionSemantic, 6 * sizeof(float),
                      QQuick3DGeometry::Attribute::ComponentType::F32Type);
         addAttribute(QQuick3DGeometry::Attribute::TargetNormalSemantic, 9 * sizeof(float),
                      QQuick3DGeometry::Attribute::ComponentType::F32Type);

         addAttribute(QQuick3DGeometry::Attribute::IndexSemantic, 0,
                      QQuick3DGeometry::Attribute::ComponentType::U32Type);

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

         for (int i = 0; i < numVertexes; ++i) {
             Vertex &v = vert[i];
             v.position = m_positions[i];
             v.normal = m_normals[i];
             v.targetPosition = m_targetPositions[i];
             v.targetNormal = m_targetNormals[i];
         }

         setStride(sizeof(Vertex));
         setVertexData(m_vertexBuffer);
         setPrimitiveType(QQuick3DGeometry::PrimitiveType::Triangles);
         setBounds(boundsMin, boundsMax);

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

     void MorphGeometry::calculateGeometry()
     {
         float dw = 10.0; // width/2
         float dh = 10.0;
         int iw = m_gridSize;
         int ih = m_gridSize;
         float wf = dw * 2 / iw; //factor grid coord => position
         float hf = dh * 2 / ih;

         m_positions.clear();
         m_indexes.clear();
         m_targetPositions.clear();
         m_targetNormals.clear();

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

         // We construct a rectangular grid of iw times ih vertices;
         // ix and iy are indices into the grid. x, y, and z are the spatial
         // coordinates we calculate for each vertex. tx, ty, and tz are the
         // coordinates for the morph target.

         for (int iy = 0; iy < ih; ++iy) {
             for (int ix = 0; ix < iw; ++ix) {
                 float x = ix * wf - dw;
                 float z = iy * hf - dh;

                 // The base shape is a cosine wave, and the corresponding normal
                 // vectors are calculated from the partial derivatives.
                 float y = 2 * qCos(x) + 3.0;
                 QVector3D normal{2 * qSin(x), 2, 0};

                 float tx = x * 1.2;
                 float tz = z * 1.2;

                 constexpr float R = 16;
                 QVector3D targetPosition;
                 QVector3D targetNormal;

                 // The morph target shape is a hemisphere. Therefore we don't have
                 // to do complex math to calculate the normal vector, since all vectors
                 // from the center are normal to the surface of a sphere.
                 if (tx*tx + tz*tz < R*R) {
                     float ty = 0.4f * qSqrt(R*R - tx*tx - tz*tz);
                     targetPosition = {tx, ty, tz};
                     targetNormal = targetPosition;
                 } else {
                     targetPosition = {tx, -3, tz};
                     targetNormal = {0, 1, 0};
                 }

                 // Finally, we make the outside edges of the shapes vertical, so they look nicer.
                 if (ix == 0 || iy == 0 || ix == iw-1 || iy == ih-1) {
                     int iix = qMin(iw-2, qMax(1, ix));
                     int iiy = qMin(ih-2, qMax(1, iy));
                     x = iix * wf - dw;
                     z = iiy * hf - dh;
                     y = -3.0;
                     targetPosition.setY(-3);
                 }

                 if (iy >= ih-2)
                     normal = {0, 0, 1};
                 else if (iy <= 1)
                     normal = {0, 0, -1};

                 m_positions.append({x, y, z});
                 m_normals.append(normal.normalized());

                 m_targetPositions.append(targetPosition);
                 m_targetNormals.append(targetNormal.normalized());

                 // Note: We only use the bounds of the target positions since they are strictly
                 // bigger than the original
                 boundsMin.setX(std::min(boundsMin.x(), targetPosition.x()));
                 boundsMin.setY(std::min(boundsMin.y(), targetPosition.y()));
                 boundsMin.setZ(std::min(boundsMin.z(), targetPosition.z()));

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

         for (int ix = 0; ix < iw - 1; ++ix) {
             for (int iy = 0; iy < ih - 1; ++iy) {
                 int idx = ix + iy * ih;
                 m_indexes << idx << idx + iw << idx + iw + 1
                           << idx << idx + iw + 1 << idx + 1;
             }
         }
     }