SphericalScanlineTextureMapper.cpp

// SPDX-License-Identifier: LGPL-2.1-or-later
//
// SPDX-FileCopyrightText: 2007 Torsten Rahn <tackat@kde.org>
// SPDX-FileCopyrightText: 2011 Bernhard Beschow <bbeschow@cs.tu-berlin.de>
//
 
#include "SphericalScanlineTextureMapper.h"
 
#include <cmath>
 
#include <QRunnable>
#include <qmath.h>
 
#include "GeoDataPolygon.h"
#include "GeoPainter.h"
#include "MarbleDebug.h"
#include "MathHelper.h"
#include "Quaternion.h"
#include "ScanlineTextureMapperContext.h"
#include "StackedTile.h"
#include "StackedTileLoader.h"
#include "TextureColorizer.h"
#include "ViewportParams.h"
 
using namespace Marble;
 
class SphericalScanlineTextureMapper::RenderJob : public QRunnable
{
public:
    RenderJob(StackedTileLoader *tileLoader, int tileLevel, QImage *canvasImage, const ViewportParams *viewport, MapQuality mapQuality, int yTop, int yBottom);
 
    void run() override;
 
private:
    StackedTileLoader *const m_tileLoader;
    const int m_tileLevel;
    QImage *const m_canvasImage;
    const ViewportParams *const m_viewport;
    const MapQuality m_mapQuality;
    int const m_yTop;
    int const m_yBottom;
};
 
SphericalScanlineTextureMapper::RenderJob::RenderJob(StackedTileLoader *tileLoader,
                                                     int tileLevel,
                                                     QImage *canvasImage,
                                                     const ViewportParams *viewport,
                                                     MapQuality mapQuality,
                                                     int yTop,
                                                     int yBottom)
    : m_tileLoader(tileLoader)
    , m_tileLevel(tileLevel)
    , m_canvasImage(canvasImage)
    , m_viewport(viewport)
    , m_mapQuality(mapQuality)
    , m_yTop(yTop)
    , m_yBottom(yBottom)
{
}
 
SphericalScanlineTextureMapper::SphericalScanlineTextureMapper(StackedTileLoader *tileLoader)
    : TextureMapperInterface()
    , m_tileLoader(tileLoader)
    , m_radius(0)
    , m_threadPool()
{
}
 
void SphericalScanlineTextureMapper::mapTexture(GeoPainter *painter,
                                                const ViewportParams *viewport,
                                                int tileZoomLevel,
                                                const QRect &dirtyRect,
                                                TextureColorizer *texColorizer)
{
    if (m_canvasImage.size() != viewport->size() || m_radius != viewport->radius()) {
        const QImage::Format optimalFormat = ScanlineTextureMapperContext::optimalCanvasImageFormat(viewport);
 
        if (m_canvasImage.size() != viewport->size() || m_canvasImage.format() != optimalFormat) {
            m_canvasImage = QImage(viewport->size(), optimalFormat);
        }
 
        if (!viewport->mapCoversViewport()) {
            m_canvasImage.fill(0);
        }
 
        m_radius = viewport->radius();
        m_repaintNeeded = true;
    }
 
    if (m_repaintNeeded) {
        mapTexture(viewport, tileZoomLevel, painter->mapQuality());
 
        if (texColorizer) {
            texColorizer->colorize(&m_canvasImage, viewport, painter->mapQuality());
        }
 
        m_repaintNeeded = false;
    }
 
    const int radius = viewport->radius();
 
    QRect rect(viewport->width() / 2 - radius, viewport->height() / 2 - radius, 2 * radius, 2 * radius);
    rect = rect.intersected(dirtyRect);
    painter->drawImage(rect, m_canvasImage, rect);
}
 
void SphericalScanlineTextureMapper::mapTexture(const ViewportParams *viewport, int tileZoomLevel, MapQuality mapQuality)
{
    // Reset backend
    m_tileLoader->resetTilehash();
 
    // Initialize needed constants:
 
    const int imageHeight = m_canvasImage.height();
    const qint64 radius = viewport->radius();
 
    // Calculate the actual y-range of the map on the screen
    const int skip = (mapQuality == LowQuality) ? 1 : 0;
    const int yTop = (imageHeight / 2 - radius >= 0) ? imageHeight / 2 - radius : 0;
    const int yBottom = (yTop == 0) ? imageHeight - skip : yTop + radius + radius - skip;
 
    const int numThreads = m_threadPool.maxThreadCount();
    const int yStep = qCeil(qreal(yBottom - yTop) / qreal(numThreads));
    for (int i = 0; i < numThreads; ++i) {
        const int yStart = yTop + i * yStep;
        const int yEnd = qMin(yBottom, yTop + (i + 1) * yStep);
        QRunnable *const job = new RenderJob(m_tileLoader, tileZoomLevel, &m_canvasImage, viewport, mapQuality, yStart, yEnd);
        m_threadPool.start(job);
    }
 
    m_threadPool.waitForDone();
 
    m_tileLoader->cleanupTilehash();
}
 
void SphericalScanlineTextureMapper::RenderJob::run()
{
    const int imageHeight = m_canvasImage->height();
    const int imageWidth = m_canvasImage->width();
    const qint64 radius = m_viewport->radius();
    const qreal inverseRadius = 1.0 / (qreal)(radius);
 
    const bool interlaced = (m_mapQuality == LowQuality);
    const bool highQuality = (m_mapQuality == HighQuality || m_mapQuality == PrintQuality);
    const bool printQuality = (m_mapQuality == PrintQuality);
 
    // Evaluate the degree of interpolation
    const int n = ScanlineTextureMapperContext::interpolationStep(m_viewport, m_mapQuality);
 
    // Calculate north pole position to decrease pole distortion later on
    Quaternion northPole = Quaternion::fromSpherical(0.0, M_PI * 0.5);
    northPole.rotateAroundAxis(m_viewport->planetAxis().inverse());
    const int northPoleX = imageWidth / 2 + (int)(radius * northPole.v[Q_X]);
    const int northPoleY = imageHeight / 2 - (int)(radius * northPole.v[Q_Y]);
 
    // Calculate axis matrix to represent the planet's rotation.
    matrix planetAxisMatrix;
    m_viewport->planetAxis().toMatrix(planetAxisMatrix);
 
    // initialize needed variables that are modified during texture mapping:
 
    ScanlineTextureMapperContext context(m_tileLoader, m_tileLevel);
    qreal lon = 0.0;
    qreal lat = 0.0;
 
    // Scanline based algorithm to texture map a sphere
    for (int y = m_yTop; y < m_yBottom; ++y) {
        // Evaluate coordinates for the 3D position vector of the current pixel
        const qreal qy = inverseRadius * (qreal)(imageHeight / 2 - y);
        const qreal qr = 1.0 - qy * qy;
 
        // rx is the radius component in x direction
        const int rx = (int)sqrt((qreal)(radius * radius - ((y - imageHeight / 2) * (y - imageHeight / 2))));
 
        // Calculate the actual x-range of the map within the current scanline.
        //
        // If the circular border of the earth disk is still visible then xLeft
        // equals the scanline position of the most left pixel that gets covered
        // by the earth disk. In terms of math this equals the half image width minus
        // the radius component on the current scanline in x direction ("rx").
        //
        // If the zoom factor is high enough then the whole screen gets covered
        // by the earth and the border of the earth disk isn't visible anymore.
        // In that situation xLeft equals zero.
        // For xRight the situation is similar.
 
        const int xLeft = (imageWidth / 2 - rx > 0) ? imageWidth / 2 - rx : 0;
        const int xRight = (imageWidth / 2 - rx > 0) ? xLeft + rx + rx : imageWidth;
 
        QRgb *scanLine = (QRgb *)(m_canvasImage->scanLine(y)) + xLeft;
 
        const int xIpLeft = (imageWidth / 2 - rx > 0) ? n * (int)(xLeft / n + 1) : 1;
        const int xIpRight = (imageWidth / 2 - rx > 0) ? n * (int)(xRight / n - 1) : n * (int)(xRight / n - 1) + 1;
 
        // Decrease pole distortion due to linear approximation ( y-axis )
        bool crossingPoleArea = false;
        if (northPole.v[Q_Z] > 0 && northPoleY - (n * 0.75) <= y && northPoleY + (n * 0.75) >= y) {
            crossingPoleArea = true;
        }
 
        int ncount = 0;
 
        for (int x = xLeft; x < xRight; ++x) {
            // Prepare for interpolation
 
            const int leftInterval = xIpLeft + ncount * n;
 
            bool interpolate = false;
            if (x >= xIpLeft && x <= xIpRight) {
                // Decrease pole distortion due to linear approximation ( x-axis )
                //                mDebug() << QStringLiteral("NorthPole X: %1, LeftInterval: %2").arg( northPoleX ).arg( leftInterval );
                if (crossingPoleArea && northPoleX >= leftInterval + n && northPoleX < leftInterval + 2 * n && x < leftInterval + 3 * n) {
                    interpolate = false;
                } else {
                    x += n - 1;
                    interpolate = !printQuality;
                    ++ncount;
                }
            } else
                interpolate = false;
 
            // Evaluate more coordinates for the 3D position vector of
            // the current pixel.
            const qreal qx = (qreal)(x - imageWidth / 2) * inverseRadius;
            const qreal qr2z = qr - qx * qx;
            const qreal qz = (qr2z > 0.0) ? sqrt(qr2z) : 0.0;
 
            // Create Quaternion from vector coordinates and rotate it
            // around globe axis
            Quaternion qpos(0.0, qx, qy, qz);
            qpos.rotateAroundAxis(planetAxisMatrix);
 
            qpos.getSpherical(lon, lat);
            //            mDebug() << QStringLiteral("lon: %1 lat: %2").arg(lon).arg(lat);
            // Approx for n-1 out of n pixels within the boundary of
            // xIpLeft to xIpRight
 
            if (interpolate) {
                if (highQuality)
                    context.pixelValueApproxF(lon, lat, scanLine, n);
                else
                    context.pixelValueApprox(lon, lat, scanLine, n);
 
                scanLine += (n - 1);
            }
 
            //          Comment out the pixelValue line and run Marble if you want
            //          to understand the interpolation:
 
            //          Uncomment the crossingPoleArea line to check precise
            //          rendering around north pole:
 
            //            if ( !crossingPoleArea )
            if (x < imageWidth) {
                if (highQuality)
                    context.pixelValueF(lon, lat, scanLine);
                else
                    context.pixelValue(lon, lat, scanLine);
            }
 
            ++scanLine;
        }
 
        // copy scanline to improve performance
        if (interlaced && y + 1 < m_yBottom) {
            const int pixelByteSize = m_canvasImage->bytesPerLine() / imageWidth;
 
            memcpy(m_canvasImage->scanLine(y + 1) + xLeft * pixelByteSize,
                   m_canvasImage->scanLine(y) + xLeft * pixelByteSize,
                   (xRight - xLeft) * pixelByteSize);
            ++y;
        }
    }
}