qt-everywhere-src-5.14.1/qtquick3d/src/runtimerender/qssgrenderray.cpp

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#include "qssgrenderray_p.h"

#include <QtQuick3DUtils/private/qssgplane_p.h>
#include <QtQuick3DUtils/private/qssgutils_p.h>

QT_BEGIN_NAMESPACE

// http://www.siggraph.org/education/materials/HyperGraph/raytrace/rayplane_intersection.htm

QSSGOption<QVector3D> QSSGRenderRay::intersect(const QSSGPlane &inPlane) const
{
    float Vd = QVector3D::dotProduct(inPlane.n, direction);
    if (std::abs(Vd) < .0001f)
        return QSSGEmpty();
    float V0 = -1.0f * (QVector3D::dotProduct(inPlane.n, origin) + inPlane.d);
    float t = V0 / Vd;
    return origin + (direction * t);
}

QSSGRenderRay::IntersectionResult QSSGRenderRay::intersectWithAABB(const QMatrix4x4 &inGlobalTransform, const QSSGBounds3 &inBounds,
                                                                       bool inForceIntersect) const
{
    // Intersect the origin with the AABB described by bounds.

    // Scan each axis separately.  This code basically finds the distance
    // distance from the origin to the near and far bbox planes for a given
    // axis.  It then divides this distance by the direction for that axis to
    // get a range of t [near,far] that the ray intersects assuming the ray is
    // described via origin + t*(direction).  Running through all three axis means
    // that you need to min/max those ranges together to find a global min/max
    // that the pick could possibly be in.

    // Transform pick origin and direction into the subset's space.
    QMatrix4x4 theOriginTransform = inGlobalTransform.inverted();

    QVector3D theTransformedOrigin = mat44::transform(theOriginTransform, origin);
    float *outOriginTransformPtr(theOriginTransform.data());
    outOriginTransformPtr[12] = outOriginTransformPtr[13] = outOriginTransformPtr[14] = 0.0f;

    QVector3D theTransformedDirection = mat44::rotate(theOriginTransform, direction);

    static const float KD_FLT_MAX = 3.40282346638528860e+38;
    static const float kEpsilon = 1e-5f;

    float theMinWinner = -KD_FLT_MAX;
    float theMaxWinner = KD_FLT_MAX;

    for (quint32 theAxis = 0; theAxis < 3; ++theAxis) {
        // Extract the ranges and direction for this axis
        float theMinBox = inBounds.minimum[theAxis];
        float theMaxBox = inBounds.maximum[theAxis];
        float theDirectionAxis = theTransformedDirection[theAxis];
        float theOriginAxis = theTransformedOrigin[theAxis];

        float theMinAxis = -KD_FLT_MAX;
        float theMaxAxis = KD_FLT_MAX;
        if (theDirectionAxis > kEpsilon) {
            theMinAxis = (theMinBox - theOriginAxis) / theDirectionAxis;
            theMaxAxis = (theMaxBox - theOriginAxis) / theDirectionAxis;
        } else if (theDirectionAxis < -kEpsilon) {
            theMinAxis = (theMaxBox - theOriginAxis) / theDirectionAxis;
            theMaxAxis = (theMinBox - theOriginAxis) / theDirectionAxis;
        } else if ((theOriginAxis < theMinBox || theOriginAxis > theMaxBox) && inForceIntersect == false) {
            // Pickray is roughly parallel to the plane of the slab
            // so, if the origin is not in the range, we have no intersection
            return IntersectionResult();
        }

        // Shrink the intersections to find the closest hit
        theMinWinner = qMax(theMinWinner, theMinAxis);
        theMaxWinner = qMin(theMaxWinner, theMaxAxis);

        if ((theMinWinner > theMaxWinner || theMaxWinner < 0) && inForceIntersect == false)
            return IntersectionResult();
    }

    QVector3D scaledDir = theTransformedDirection * theMinWinner;
    QVector3D newPosInLocal = theTransformedOrigin + scaledDir;
    QVector3D newPosInGlobal = mat44::transform(inGlobalTransform, newPosInLocal);
    QVector3D cameraToLocal = origin - newPosInGlobal;

    float rayLengthSquared = vec3::magnitudeSquared(cameraToLocal);

    float xRange = inBounds.maximum.x() - inBounds.minimum.x();
    float yRange = inBounds.maximum.y() - inBounds.minimum.y();

    QVector2D relXY;
    relXY.setX((newPosInLocal[0] - inBounds.minimum.x()) / xRange);
    relXY.setY((newPosInLocal[1] - inBounds.minimum.y()) / yRange);

    return IntersectionResult(rayLengthSquared, relXY, newPosInGlobal);
}

QSSGOption<QVector2D> QSSGRenderRay::relative(const QMatrix4x4 &inGlobalTransform,
                                                     const QSSGBounds3 &inBounds,
                                                     QSSGRenderBasisPlanes inPlane) const
{
    QMatrix4x4 theOriginTransform = inGlobalTransform.inverted();

    QVector3D theTransformedOrigin = mat44::transform(theOriginTransform, origin);
    float *outOriginTransformPtr(theOriginTransform.data());
    outOriginTransformPtr[12] = outOriginTransformPtr[13] = outOriginTransformPtr[14] = 0.0f;
    QVector3D theTransformedDirection = mat44::rotate(theOriginTransform, direction);

    // The XY plane is going to be a plane with either positive or negative Z direction that runs
    // through
    QVector3D theDirection(0, 0, 1);
    QVector3D theRight(1, 0, 0);
    QVector3D theUp(0, 1, 0);
    switch (inPlane) {
    case QSSGRenderBasisPlanes::XY:
        break;
    case QSSGRenderBasisPlanes::XZ:
        theDirection = QVector3D(0, 1, 0);
        theUp = QVector3D(0, 0, 1);
        break;
    case QSSGRenderBasisPlanes::YZ:
        theDirection = QVector3D(1, 0, 0);
        theRight = QVector3D(0, 0, 1);
        break;
    }
    QSSGPlane thePlane(theDirection,
                         QVector3D::dotProduct(theDirection, theTransformedDirection) > 0.0f
                                 ? QVector3D::dotProduct(theDirection, inBounds.maximum)
                                 : QVector3D::dotProduct(theDirection, inBounds.minimum));

    QSSGRenderRay relativeRay(theTransformedOrigin, theTransformedDirection);
    QSSGOption<QVector3D> localIsect = relativeRay.intersect(thePlane);
    if (localIsect.hasValue()) {
        float xRange = QVector3D::dotProduct(theRight, inBounds.maximum) - QVector3D::dotProduct(theRight, inBounds.minimum);
        float yRange = QVector3D::dotProduct(theUp, inBounds.maximum) - QVector3D::dotProduct(theUp, inBounds.minimum);
        float xOrigin = xRange / 2.0f + QVector3D::dotProduct(theRight, inBounds.minimum);
        float yOrigin = yRange / 2.0f + QVector3D::dotProduct(theUp, inBounds.minimum);
        return QVector2D((QVector3D::dotProduct(theRight, *localIsect) - xOrigin) / xRange,
                         (QVector3D::dotProduct(theUp, *localIsect) - yOrigin) / yRange);
    }
    return QSSGEmpty();
}

QT_END_NAMESPACE