Qt Quick 3D - Custom Geometry Example | Qt Quick 3D 6.5.3
Description: Demonstrates providing custom vertex data from C++.

- Qt 6.5
- Qt Quick 3D
- Qt Quick 3D Examples and Tutorials
- Qt Quick 3D - Custom Geometry Example
- Qt Quick 3D | Commercial or GPLv3

# Qt Quick 3D - Custom Geometry Example

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

     #include "examplegeometry.h"
     #include <QRandomGenerator>
     #include <QVector3D>

     ExampleTriangleGeometry::ExampleTriangleGeometry()
     {
         updateData();
     }

     void ExampleTriangleGeometry::setNormals(bool enable)
     {
         if (m_hasNormals == enable)
             return;

         m_hasNormals = enable;
         emit normalsChanged();
         updateData();
         update();
     }

     void ExampleTriangleGeometry::setNormalXY(float xy)
     {
         if (m_normalXY == xy)
             return;

         m_normalXY = xy;
         emit normalXYChanged();
         updateData();
         update();
     }

     void ExampleTriangleGeometry::setUV(bool enable)
     {
         if (m_hasUV == enable)
             return;

         m_hasUV = enable;
         emit uvChanged();
         updateData();
         update();
     }

     void ExampleTriangleGeometry::setUVAdjust(float f)
     {
         if (m_uvAdjust == f)
             return;

         m_uvAdjust = f;
         emit uvAdjustChanged();
         updateData();
         update();
     }

     void ExampleTriangleGeometry::updateData()
     {
         clear();

         int stride = 3 * sizeof(float);
         if (m_hasNormals)
             stride += 3 * sizeof(float);
         if (m_hasUV)
             stride += 2 * sizeof(float);

         QByteArray vertexData(3 * stride, Qt::Initialization::Uninitialized);
         float *p = reinterpret_cast<float *>(vertexData.data());

         // a triangle, front face = counter-clockwise
         *p++ = -1.0f; *p++ = -1.0f; *p++ = 0.0f;
         if (m_hasNormals) {
             *p++ = m_normalXY; *p++ = m_normalXY; *p++ = 1.0f;
         }
         if (m_hasUV) {
             *p++ = 0.0f + m_uvAdjust; *p++ = 0.0f + m_uvAdjust;
         }
         *p++ = 1.0f; *p++ = -1.0f; *p++ = 0.0f;
         if (m_hasNormals) {
             *p++ = m_normalXY; *p++ = m_normalXY; *p++ = 1.0f;
         }
         if (m_hasUV) {
             *p++ = 1.0f - m_uvAdjust; *p++ = 0.0f + m_uvAdjust;
         }
         *p++ = 0.0f; *p++ = 1.0f; *p++ = 0.0f;
         if (m_hasNormals) {
             *p++ = m_normalXY; *p++ = m_normalXY; *p++ = 1.0f;
         }
         if (m_hasUV) {
             *p++ = 1.0f - m_uvAdjust; *p++ = 1.0f - m_uvAdjust;
         }

         setVertexData(vertexData);
         setStride(stride);
         setBounds(QVector3D(-1.0f, -1.0f, 0.0f), QVector3D(+1.0f, +1.0f, 0.0f));

         setPrimitiveType(QQuick3DGeometry::PrimitiveType::Triangles);

         addAttribute(QQuick3DGeometry::Attribute::PositionSemantic,
                      0,
                      QQuick3DGeometry::Attribute::F32Type);

         if (m_hasNormals) {
             addAttribute(QQuick3DGeometry::Attribute::NormalSemantic,
                          3 * sizeof(float),
                          QQuick3DGeometry::Attribute::F32Type);
         }

         if (m_hasUV) {
             addAttribute(QQuick3DGeometry::Attribute::TexCoordSemantic,
                          m_hasNormals ? 6 * sizeof(float) : 3 * sizeof(float),
                          QQuick3DGeometry::Attribute::F32Type);
         }
     }

     ExamplePointGeometry::ExamplePointGeometry()
     {
         updateData();
     }

     void ExamplePointGeometry::updateData()
     {
         clear();

         constexpr auto randomFloat = [](const float lowest, const float highest) -> float {
             return lowest + QRandomGenerator::global()->generateDouble() * (highest - lowest);
         };
         constexpr int NUM_POINTS = 2000;
         constexpr int stride = 3 * sizeof(float);

         QByteArray vertexData;
         vertexData.resize(NUM_POINTS * stride);
         float *p = reinterpret_cast<float *>(vertexData.data());

         for (int i = 0; i < NUM_POINTS; ++i) {
             *p++ = randomFloat(-5.0f, +5.0f);
             *p++ = randomFloat(-5.0f, +5.0f);
             *p++ = 0.0f;
         }

         setVertexData(vertexData);
         setStride(stride);
         setBounds(QVector3D(-5.0f, -5.0f, 0.0f), QVector3D(+5.0f, +5.0f, 0.0f));

         setPrimitiveType(QQuick3DGeometry::PrimitiveType::Points);

         addAttribute(QQuick3DGeometry::Attribute::PositionSemantic,
                      0,
                      QQuick3DGeometry::Attribute::F32Type);
     }