polylineobject.cpp

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//=============================================================================================================
 
//=============================================================================================================
// INCLUDES
//=============================================================================================================
 
#include "polylineobject.h"
 
//=============================================================================================================
// QT INCLUDES
//=============================================================================================================
 
#include <QMatrix4x4>
#include <QQuaternion>
#include <QVector3D>
#include <QtMath>
 
namespace DISP3DLIB
{
 
//=============================================================================================================
// DEFINE MEMBER METHODS
//=============================================================================================================
 
//=============================================================================================================
 
PolylineObject::PolylineObject()
: m_iIndexCount(0)
, m_iInstanceCount(0)
, m_fRadius(0.0015f)
, m_startColor(QColor(60, 120, 255))
, m_endColor(QColor(255, 80, 40))
, m_bVisible(true)
{
    createSegmentGeometry();
}
 
//=============================================================================================================
 
PolylineObject::~PolylineObject() = default;
 
//=============================================================================================================
 
void PolylineObject::setPoints(const QVector<Eigen::Vector3f>& vecPoints)
{
    // A single point has no segment, so it is treated the same as no data at
    // all rather than drawn as a degenerate line.
    if (vecPoints.size() < 2) {
        clear();
        return;
    }
 
    m_vecPoints = vecPoints;
    buildInstances();
}
 
//=============================================================================================================
 
void PolylineObject::clear()
{
    m_vecPoints.clear();
    m_instanceData.clear();
    m_iInstanceCount = 0;
    ++m_instanceGeneration;
}
 
//=============================================================================================================
 
void PolylineObject::setRadius(float fRadius)
{
    m_fRadius = fRadius;
    buildInstances();
}
 
//=============================================================================================================
 
void PolylineObject::setGradient(const QColor& startColor,
                                 const QColor& endColor)
{
    m_startColor = startColor;
    m_endColor = endColor;
    buildInstances();
}
 
//=============================================================================================================
 
void PolylineObject::createSegmentGeometry()
{
    if (!m_vertexData.isEmpty()) {
        return;
    }
 
    // Unit cylinder along Y, height 1 and radius 1, scaled and rotated per
    // instance. Eight segments is enough for a thin line and keeps the vertex
    // count low, since a long path can have thousands of instances.
    const int iSegments = 8;
    const float fHalfHeight = 0.5f;
 
    std::vector<VertexData> vertices;
    std::vector<quint32> indices;
 
    for (int i = 0; i < iSegments; ++i) {
        const float fAngle = 2.0f * static_cast<float>(M_PI) * static_cast<float>(i) / static_cast<float>(iSegments);
        const float x = std::cos(fAngle);
        const float z = std::sin(fAngle);
 
        QVector3D normal(x, 0.0f, z);
        normal.normalize();
 
        vertices.push_back({x, fHalfHeight, z, normal.x(), normal.y(), normal.z()});
        vertices.push_back({x, -fHalfHeight, z, normal.x(), normal.y(), normal.z()});
    }
 
    for (int i = 0; i < iSegments; ++i) {
        const quint32 uTop = static_cast<quint32>(i * 2);
        const quint32 uBottom = uTop + 1;
        const quint32 uNextTop = static_cast<quint32>(((i + 1) % iSegments) * 2);
        const quint32 uNextBottom = uNextTop + 1;
 
        indices.push_back(uTop);
        indices.push_back(uBottom);
        indices.push_back(uNextTop);
 
        indices.push_back(uNextTop);
        indices.push_back(uBottom);
        indices.push_back(uNextBottom);
    }
 
    m_vertexData = QByteArray(reinterpret_cast<const char*>(vertices.data()),
                              static_cast<qsizetype>(vertices.size() * sizeof(VertexData)));
    m_indexData = QByteArray(reinterpret_cast<const char*>(indices.data()),
                             static_cast<qsizetype>(indices.size() * sizeof(quint32)));
    m_iIndexCount = static_cast<int>(indices.size());
    ++m_geometryGeneration;
}
 
//=============================================================================================================
 
void PolylineObject::buildInstances()
{
    if (m_vecPoints.size() < 2) {
        m_instanceData.clear();
        m_iInstanceCount = 0;
        return;
    }
 
    const int iSegmentCount = m_vecPoints.size() - 1;
    std::vector<InstanceData> instances;
    instances.reserve(static_cast<size_t>(iSegmentCount));
 
    const float fLastStep = static_cast<float>(iSegmentCount - 1);
 
    for (int i = 0; i < iSegmentCount; ++i) {
        const Eigen::Vector3f& vecStart = m_vecPoints.at(i);
        const Eigen::Vector3f& vecEnd = m_vecPoints.at(i + 1);
 
        const QVector3D start(vecStart.x(), vecStart.y(), vecStart.z());
        const QVector3D end(vecEnd.x(), vecEnd.y(), vecEnd.z());
 
        const QVector3D direction = end - start;
        const float fLength = direction.length();
 
        // Two consecutive fits can land on the same position when the subject
        // does not move. Such a segment has no direction to orient a cylinder
        // by, so it is skipped instead of producing a NaN rotation.
        //
        // The threshold has to be far below anything physical rather than
        // qFuzzyIsNull, whose tolerance for float is 1e-5. Positions are in
        // metres, so that would discard every step under ten micrometres and
        // punch gaps into the path of a slowly drifting subject. A picometre
        // is small enough that only genuinely coincident points are dropped,
        // and large enough to keep the division below well conditioned.
        constexpr float fMinSegmentLength = 1.0e-12f;
        if (fLength < fMinSegmentLength) {
            continue;
        }
 
        QMatrix4x4 model;
        model.translate((start + end) * 0.5f);
        model.rotate(QQuaternion::rotationTo(QVector3D(0.0f, 1.0f, 0.0f),
                                             direction / fLength));
        model.scale(m_fRadius, fLength, m_fRadius);
 
        InstanceData instance{};
        memcpy(instance.model, model.constData(), 16 * sizeof(float));
 
        // Grade from the start colour to the end colour so the direction the
        // path was travelled in is visible without extra decoration.
        const float fRatio = (fLastStep > 0.0f) ? (static_cast<float>(i) / fLastStep) : 0.0f;
        instance.color[0] = static_cast<float>(m_startColor.redF() + (m_endColor.redF() - m_startColor.redF()) * fRatio);
        instance.color[1] = static_cast<float>(m_startColor.greenF() + (m_endColor.greenF() - m_startColor.greenF()) * fRatio);
        instance.color[2] = static_cast<float>(m_startColor.blueF() + (m_endColor.blueF() - m_startColor.blueF()) * fRatio);
        instance.color[3] = 1.0f;
        instance.isSelected = 0.0f;
 
        instances.push_back(instance);
    }
 
    m_instanceData = QByteArray(reinterpret_cast<const char*>(instances.data()),
                                static_cast<qsizetype>(instances.size() * sizeof(InstanceData)));
    m_iInstanceCount = static_cast<int>(instances.size());
    ++m_instanceGeneration;
}
 
//=============================================================================================================
 
InstancedStreams PolylineObject::streams() const
{
    return {{m_vertexData.constData(), quint32(m_vertexData.size()), m_geometryGeneration},
            {m_indexData.constData(), quint32(m_indexData.size()), m_geometryGeneration},
            {m_instanceData.constData(), quint32(m_iInstanceCount * sizeof(InstanceData)), m_instanceGeneration},
            m_iIndexCount,
            m_iInstanceCount};
}
 
} // namespace DISP3DLIB