qssgrendercamera.cpp

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// Copyright (C) 2008-2012 NVIDIA Corporation.
// Copyright (C) 2019 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
 
 
#include "qssgrendercamera_p.h"
 
#include <QtQuick3DRuntimeRender/private/qssgrendererutil_p.h>
 
#include <QtQuick3DUtils/private/qssgutils_p.h>
 
#include <QtGui/QVector2D>
 
#include <qmath.h>
 
QT_BEGIN_NAMESPACE
 
namespace {
 
float getAspectRatio(const QRectF &inViewport)
{
    return inViewport.height() != 0 ? inViewport.width() / inViewport.height() : 0.0f;
}
 
}
 
QSSGRenderCamera::QSSGRenderCamera(QSSGRenderGraphObject::Type type)
    : QSSGRenderNode(type)
    , clipNear(10)
    , clipFar(10000)
    , fov(qDegreesToRadians(60.0f))
    , fovHorizontal(false)
    , enableFrustumClipping(true)
{
    Q_ASSERT(QSSGRenderCamera::isCamera(type));
    markDirty(DirtyFlag::CameraDirty);
}
 
// Code for testing
QSSGCameraGlobalCalculationResult QSSGRenderCamera::calculateGlobalVariables(const QRectF &inViewport)
{
    bool wasDirty = QSSGRenderNode::calculateGlobalVariables();
    return QSSGCameraGlobalCalculationResult{ wasDirty, calculateProjection(inViewport) };
}
 
bool QSSGRenderCamera::calculateProjection(const QRectF &inViewport)
{
    bool retval = false;
 
    const bool argumentsChanged = inViewport != previousInViewport;
    if (!argumentsChanged && !isDirty(DirtyFlag::CameraDirty))
        return true;
    previousInViewport = inViewport;
    clearDirty(DirtyFlag::CameraDirty);
 
    switch (type) {
    case QSSGRenderGraphObject::Type::OrthographicCamera:
        retval = computeFrustumOrtho(inViewport);
        break;
    case QSSGRenderGraphObject::Type::PerspectiveCamera:
        retval = computeFrustumPerspective(inViewport);
        break;
    case QSSGRenderGraphObject::Type::CustomCamera:
        retval = true; // Do nothing
        break;
    case QSSGRenderGraphObject::Type::CustomFrustumCamera:
        retval = computeCustomFrustum(inViewport);
        break;
    default:
        Q_UNREACHABLE();
    }
 
    if (retval) {
        float *writePtr(projection.data());
        frustumScale.setX(writePtr[0]);
        frustumScale.setY(writePtr[5]);
    }
    return retval;
}
 
//==============================================================================
bool QSSGRenderCamera::computeFrustumPerspective(const QRectF &inViewport)
{
    projection = QMatrix4x4();
    projection.perspective(qRadiansToDegrees(verticalFov(inViewport)), getAspectRatio(inViewport), clipNear, clipFar);
    return true;
}
 
bool QSSGRenderCamera::computeCustomFrustum(const QRectF &inViewport)
{
    Q_UNUSED(inViewport);
    projection.setToIdentity();
    projection.frustum(left, right, bottom, top, clipNear, clipFar);
    return true;
}
 
//==============================================================================
bool QSSGRenderCamera::computeFrustumOrtho(const QRectF &inViewport)
{
    projection = QMatrix4x4();
    float halfWidth = inViewport.width() / 2.0f / horizontalMagnification / dpr;
    float halfHeight = inViewport.height() / 2.0f / verticalMagnification / dpr;
    projection.ortho(-halfWidth, halfWidth, -halfHeight, halfHeight, clipNear, clipFar);
    return true;
}
 
float QSSGRenderCamera::getOrthographicScaleFactor(const QRectF &inViewport) const
{
    Q_UNUSED(inViewport);
    return qMax(horizontalMagnification, verticalMagnification);
}
 
static QQuaternion rotationQuaternionForLookAt(const QVector3D &sourcePosition,
                                               const QVector3D &sourceDirection,
                                               const QVector3D &targetPosition,
                                               const QVector3D &upDirection)
{
    QVector3D targetDirection = sourcePosition - targetPosition;
    targetDirection.normalize();
 
    QVector3D rotationAxis = QVector3D::crossProduct(sourceDirection, targetDirection);
 
    const QVector3D normalizedAxis = rotationAxis.normalized();
    if (qFuzzyIsNull(normalizedAxis.lengthSquared()))
        rotationAxis = upDirection;
 
    float dot = QVector3D::dotProduct(sourceDirection, targetDirection);
    float rotationAngle = float(qRadiansToDegrees(qAcos(qreal(dot))));
 
    return QQuaternion::fromAxisAndAngle(rotationAxis, rotationAngle);
}
 
void QSSGRenderCamera::lookAt(const QVector3D &inCameraPos, const QVector3D &inUpDir, const QVector3D &inTargetPos, const QVector3D &pivot)
{
    QQuaternion rotation = rotationQuaternionForLookAt(inCameraPos, getScalingCorrectDirection(), inTargetPos, inUpDir.normalized());
    globalTransform = localTransform = QSSGRenderNode::calculateTransformMatrix(inCameraPos, QSSGRenderNode::initScale, pivot, rotation);
    QSSGRenderNode::markDirty(QSSGRenderNode::DirtyFlag::TransformDirty);
}
 
void QSSGRenderCamera::calculateViewProjectionMatrix(QMatrix4x4 &outMatrix) const
{
    QMatrix4x4 nonScaledGlobal(Qt::Uninitialized);
    nonScaledGlobal.setColumn(0, globalTransform.column(0).normalized());
    nonScaledGlobal.setColumn(1, globalTransform.column(1).normalized());
    nonScaledGlobal.setColumn(2, globalTransform.column(2).normalized());
    nonScaledGlobal.setColumn(3, globalTransform.column(3));
    outMatrix = projection * nonScaledGlobal.inverted();
}
 
void QSSGRenderCamera::calculateViewProjectionWithoutTranslation(float clipNear, float clipFar, QMatrix4x4 &outMatrix) const
{
    if (qFuzzyIsNull(clipFar - clipNear)) {
        qWarning() << "QSSGRenderCamera::calculateViewProjection: far == near";
        return;
    }
 
    QMatrix4x4 proj = projection;
    proj(2, 2) = -(clipFar + clipNear) / (clipFar - clipNear);
    proj(2, 3) = -2 * clipFar * clipNear / (clipFar - clipNear);
    QMatrix4x4 nonScaledGlobal(Qt::Uninitialized);
    nonScaledGlobal.setColumn(0, globalTransform.column(0).normalized());
    nonScaledGlobal.setColumn(1, globalTransform.column(1).normalized());
    nonScaledGlobal.setColumn(2, globalTransform.column(2).normalized());
    nonScaledGlobal.setColumn(3, QVector4D(0, 0, 0, 1));
    outMatrix = proj * nonScaledGlobal.inverted();
}
 
QSSGRenderRay QSSGRenderCamera::unproject(const QVector2D &inViewportRelativeCoords,
                                              const QRectF &inViewport) const
{
    QSSGRenderRay theRay;
    QVector2D normalizedCoords = relativeToNormalizedCoordinates(inViewport, inViewportRelativeCoords);
    QVector3D &outOrigin(theRay.origin);
    QVector3D &outDir(theRay.direction);
    QVector2D inverseFrustumScale(1.0f / frustumScale.x(), 1.0f / frustumScale.y());
    QVector2D scaledCoords(inverseFrustumScale.x() * normalizedCoords.x(), inverseFrustumScale.y() * normalizedCoords.y());
 
    if (type == QSSGRenderCamera::Type::OrthographicCamera) {
        outOrigin.setX(scaledCoords.x());
        outOrigin.setY(scaledCoords.y());
        outOrigin.setZ(0.0f);
 
        outDir.setX(0.0f);
        outDir.setY(0.0f);
        outDir.setZ(-1.0f);
    } else {
        outOrigin.setX(0.0f);
        outOrigin.setY(0.0f);
        outOrigin.setZ(0.0f);
 
        outDir.setX(scaledCoords.x());
        outDir.setY(scaledCoords.y());
        outDir.setZ(-1.0f);
    }
 
    outOrigin = mat44::transform(globalTransform, outOrigin);
    QMatrix3x3 theNormalMatrix = calculateNormalMatrix();
 
    outDir = mat33::transform(theNormalMatrix, outDir);
    outDir.normalize();
 
    return theRay;
}
 
QVector3D QSSGRenderCamera::unprojectToPosition(const QVector3D &inGlobalPos, const QSSGRenderRay &inRay) const
{
    QVector3D theCameraDir = getDirection();
    QVector3D theObjGlobalPos = inGlobalPos;
    float theDistance = -1.0f * QVector3D::dotProduct(theObjGlobalPos, theCameraDir);
    QSSGPlane theCameraPlane(theCameraDir, theDistance);
    return QSSGRenderRay::intersect(theCameraPlane, inRay).value_or(QVector3D{});
}
 
float QSSGRenderCamera::verticalFov(float aspectRatio) const
{
    return fovHorizontal ? float(2.0 * qAtan(qTan(qreal(fov) / 2.0) / qreal(aspectRatio))) : fov;
}
 
float QSSGRenderCamera::verticalFov(const QRectF &inViewport) const
{
    return verticalFov(getAspectRatio(inViewport));
}
 
void QSSGRenderCamera::markDirty(DirtyFlag dirtyFlag)
{
    cameraDirtyFlags |= FlagT(dirtyFlag);
    QSSGRenderNode::markDirty(QSSGRenderNode::DirtyFlag::SubNodeDirty);
}
 
void QSSGRenderCamera::clearDirty(DirtyFlag dirtyFlag)
{
    cameraDirtyFlags &= ~FlagT(dirtyFlag);
    QSSGRenderNode::clearDirty(QSSGRenderNode::DirtyFlag::SubNodeDirty);
}
 
static float getZNear(const QMatrix4x4 &projection)
{
    const float *data = projection.constData();
    QSSGPlane plane(QVector3D(data[3] + data[2], data[7] + data[6], data[11] + data[10]), -data[15] - data[14]);
    plane.normalize();
    return plane.d;
}
 
static QVector2D getViewportHalfExtents(const QMatrix4x4 &projection) {
    const float *data = projection.constData();
 
    QSSGPlane nearPlane(QVector3D(data[3] + data[2], data[7] + data[6], data[11] + data[10]), -data[15] - data[14]);
    nearPlane.normalize();
    QSSGPlane rightPlane(QVector3D(data[3] - data[0], data[7] - data[4], data[11] - data[8]), -data[15] + data[12]);
    rightPlane.normalize();
    QSSGPlane topPlane(QVector3D(data[3] - data[1], data[7] - data[5], data[11] - data[9]), -data[15] + data[13]);
    topPlane.normalize();
 
    // Get intersection the 3 planes
    float denom = QVector3D::dotProduct(QVector3D::crossProduct(nearPlane.n, rightPlane.n), topPlane.n);
    if (qFuzzyIsNull(denom))
        return QVector2D();
 
    QVector3D intersection = (QVector3D::crossProduct(rightPlane.n, topPlane.n) * nearPlane.d +
                             (QVector3D::crossProduct(topPlane.n, nearPlane.n) * rightPlane.d) +
                             (QVector3D::crossProduct(nearPlane.n, rightPlane.n) * topPlane.d)) / denom;
 
    return QVector2D(intersection.x(), intersection.y());
}
 
float QSSGRenderCamera::getLevelOfDetailMultiplier() const
{
    if (type == QSSGRenderGraphObject::Type::OrthographicCamera)
        return getViewportHalfExtents(projection).x();
 
    float zn = getZNear(projection);
    float width = getViewportHalfExtents(projection).x() * 2.0;
    return 1.0 / (zn / width);
 
}
 
QT_END_NAMESPACE