Implement volume rendering support

New subclass of QCustom3DItem, QCustom3DVolume is provided.
The documentation for the example will be done in a separate commit.

Change-Id: Idb3fdb0654c6bec7606ca012b75852a5a8412397
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

1 files changed, 179 insertions, 0 deletions

diff --git a/examples/datavisualization/volumetric/volumetric.cpp b/examples/datavisualization/volumetric/volumetric.cpp
new file mode 100644
index 00000000..a9233cab
--- /dev/null
+++ b/examples/datavisualization/volumetric/volumetric.cpp
@@ -0,0 +1,179 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc
+** All rights reserved.
+** For any questions to Digia, please use contact form at http://qt.digia.com
+**
+** This file is part of the QtDataVisualization module.
+**
+** Licensees holding valid Qt Enterprise licenses may use this file in
+** accordance with the Qt Enterprise License Agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.
+**
+** If you have questions regarding the use of this file, please use
+** contact form at http://qt.digia.com
+**
+****************************************************************************/
+
+#include "volumetric.h"
+#include <QtDataVisualization/qvalue3daxis.h>
+#include <QtDataVisualization/q3dscene.h>
+#include <QtDataVisualization/q3dcamera.h>
+#include <QtDataVisualization/q3dtheme.h>
+#include <QtCore/qmath.h>
+#include <QtGui/QRgb>
+#include <QtWidgets/QLabel>
+#include <QtCore/QDebug>
+
+using namespace QtDataVisualization;
+
+const int textureSize = 256;
+
+VolumetricModifier::VolumetricModifier(Q3DScatter *scatter)
+    : m_graph(scatter),
+      m_volumeItem(0),
+      m_sliceIndexX(textureSize / 2),
+      m_sliceIndexY(textureSize / 4),
+      m_sliceIndexZ(textureSize / 2)
+{
+    m_graph->activeTheme()->setType(Q3DTheme::ThemeQt);
+    m_graph->setShadowQuality(QAbstract3DGraph::ShadowQualityNone);
+    m_graph->scene()->activeCamera()->setCameraPreset(Q3DCamera::CameraPresetFront);
+    m_graph->setOrthoProjection(true);
+
+    createVolume();
+
+    m_graph->addCustomItem(m_volumeItem);
+    m_graph->setMeasureFps(true);
+
+    QObject::connect(m_graph->scene()->activeCamera(), &Q3DCamera::zoomLevelChanged, this,
+                     &VolumetricModifier::handleZoomLevelChange);
+    QObject::connect(m_graph, &QAbstract3DGraph::currentFpsChanged, this,
+                     &VolumetricModifier::handleFpsChange);
+}
+
+VolumetricModifier::~VolumetricModifier()
+{
+    delete m_graph;
+}
+
+void VolumetricModifier::setFpsLabel(QLabel *fpsLabel)
+{
+    m_fpsLabel = fpsLabel;
+}
+
+void VolumetricModifier::sliceX(int enabled)
+{
+    m_volumeItem->setSliceIndexX(enabled ? m_sliceIndexX : -1);
+}
+
+void VolumetricModifier::sliceY(int enabled)
+{
+    m_volumeItem->setSliceIndexY(enabled ? m_sliceIndexY : -1);
+}
+
+void VolumetricModifier::sliceZ(int enabled)
+{
+    m_volumeItem->setSliceIndexZ(enabled ? m_sliceIndexZ : -1);
+}
+
+void VolumetricModifier::adjustSliceX(int value)
+{
+    m_sliceIndexX = value / (1024 / textureSize);
+    if (m_volumeItem->sliceIndexX() != -1)
+        m_volumeItem->setSliceIndexX(m_sliceIndexX);
+}
+
+void VolumetricModifier::adjustSliceY(int value)
+{
+    m_sliceIndexY = value / (1024 / textureSize * 2);
+    if (m_volumeItem->sliceIndexY() != -1)
+        m_volumeItem->setSliceIndexY(m_sliceIndexY);
+}
+
+void VolumetricModifier::adjustSliceZ(int value)
+{
+    m_sliceIndexZ = value / (1024 / textureSize);
+    if (m_volumeItem->sliceIndexZ() != -1)
+        m_volumeItem->setSliceIndexZ(m_sliceIndexZ);
+}
+
+void VolumetricModifier::handleZoomLevelChange()
+{
+    // Zooming inside volumetric object causes ugly clipping issues, so restrict zoom level a bit
+    if (m_graph->scene()->activeCamera()->zoomLevel() > 220)
+        m_graph->scene()->activeCamera()->setZoomLevel(220);
+}
+
+void VolumetricModifier::handleFpsChange(qreal fps)
+{
+    const QString fpsFormat = QStringLiteral("Fps: %1");
+    int fps10 = int(fps * 10.0);
+    m_fpsLabel->setText(fpsFormat.arg(QString::number(qreal(fps10) / 10.0)));
+}
+
+void VolumetricModifier::createVolume()
+{
+    m_volumeItem = new QCustom3DVolume;
+    m_volumeItem->setScaling(QVector3D(2.0f, 1.0f, 2.0f));
+    m_volumeItem->setTextureWidth(textureSize);
+    m_volumeItem->setTextureHeight(textureSize / 2);
+    m_volumeItem->setTextureDepth(textureSize);
+    m_volumeItem->setTextureFormat(QImage::Format_Indexed8);
+
+    // Generate color table. First color is fully transparent used to fill outer
+    // portions of the volume. The second, red layer, is somewhat transparent.
+    // Rest of to colors are opaque.
+    QVector<QRgb> colors;
+    colors.resize(256);
+
+    colors[0] = qRgba(0, 0, 0, 0);
+    for (int i = 1; i < 256; i++) {
+        if (i < 60) {
+            colors[i] = qRgba((i * 2) + 120, 0, 0, 100);
+        } else if (i < 120) {
+            colors[i] = qRgba(0, ((i - 60) * 2) + 120, 0, 255);
+        } else if (i < 180) {
+            colors[i] = qRgba(0, 0, ((i - 120) * 2) + 120, 255);
+        } else {
+            colors[i] = qRgba(i, i, i, 255);
+        }
+    }
+    m_volumeItem->setColorTable(colors);
+
+    // Generate texture data for an half-ellipsoid.
+    // This can take a while if the dimensions are large.
+    // Note that in real world cases, the texture data is usually be supplied
+    // as a stack of slice images.
+
+    QVector<uchar> *textureData = new QVector<uchar>(textureSize * textureSize * textureSize / 2);
+
+    QVector3D midPoint(float(textureSize) / 2.0f,
+                       float(textureSize) / 2.0f,
+                       float(textureSize) / 2.0f);
+
+    int index = 0;
+    for (int i = 0; i < textureSize; i++) {
+        for (int j = 0; j < textureSize / 2; j++) {
+            for (int k = 0; k < textureSize; k++) {
+                int colorIndex = 0;
+                // Take a slice out of the ellipsoid
+                if (i >= textureSize / 2 || j >= textureSize / 4 || k >= textureSize / 2) {
+                    QVector3D distVec = QVector3D(float(k), float(j * 2), float(i)) - midPoint;
+                    float adjLen = qMin(255.0f, (distVec.length() * float(textureSize / 128)));
+                    if (adjLen < 230)
+                        colorIndex = 255 - int(adjLen);
+                    else
+                        colorIndex = 0;
+                }
+
+                (*textureData)[index] = colorIndex;
+                index++;
+            }
+        }
+    }
+
+    m_volumeItem->setTextureData(textureData);
+}
+