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newtechnology

Question about XNACollision

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newtechnology    1955

XNACollision does this for testing a AABB-frustum. It converts AABB to OBB and then does intersection tests.

Isn't this complex/slower compared to AABB-frustum test?

//-----------------------------------------------------------------------------
// Exact axis alinged box vs frustum test.  Constructs an oriented box and uses
// the oriented box vs frustum test.
//
// Return values: 0 = no intersection, 
//                1 = intersection, 
//                2 = box is completely inside frustum
//-----------------------------------------------------------------------------
INT IntersectAxisAlignedBoxFrustum( const AxisAlignedBox* pVolumeA, const Frustum* pVolumeB )
{
    XMASSERT( pVolumeA );
    XMASSERT( pVolumeB );
 
    // Make the axis aligned box oriented and do an OBB vs frustum test.
    OrientedBox BoxA;
 
    BoxA.Center = pVolumeA->Center;
    BoxA.Extents = pVolumeA->Extents;
    BoxA.Orientation.x = 0.0f;
    BoxA.Orientation.y = 0.0f;
    BoxA.Orientation.z = 0.0f;
    BoxA.Orientation.w = 1.0f;
 
    return IntersectOrientedBoxFrustum( &BoxA, pVolumeB );
}

INT IntersectOrientedBoxFrustum( const OrientedBox* pVolumeA, const Frustum* pVolumeB )
{
    XMASSERT( pVolumeA );
    XMASSERT( pVolumeB );
 
    static const XMVECTORI32 SelectY =
    {
        XM_SELECT_0, XM_SELECT_1, XM_SELECT_0, XM_SELECT_0
    };
    static const XMVECTORI32 SelectZ =
    {
        XM_SELECT_0, XM_SELECT_0, XM_SELECT_1, XM_SELECT_0
    };
 
    XMVECTOR Zero = XMVectorZero();
 
    // Build the frustum planes.
    XMVECTOR Planes[6];
    Planes[0] = XMVectorSet( 0.0f, 0.0f, -1.0f, pVolumeB->Near );
    Planes[1] = XMVectorSet( 0.0f, 0.0f, 1.0f, -pVolumeB->Far );
    Planes[2] = XMVectorSet( 1.0f, 0.0f, -pVolumeB->RightSlope, 0.0f );
    Planes[3] = XMVectorSet( -1.0f, 0.0f, pVolumeB->LeftSlope, 0.0f );
    Planes[4] = XMVectorSet( 0.0f, 1.0f, -pVolumeB->TopSlope, 0.0f );
    Planes[5] = XMVectorSet( 0.0f, -1.0f, pVolumeB->BottomSlope, 0.0f );
 
    // Load origin and orientation of the frustum.
    XMVECTOR Origin = XMLoadFloat3( &pVolumeB->Origin );
    XMVECTOR FrustumOrientation = XMLoadFloat4( &pVolumeB->Orientation );
 
    XMASSERT( XMQuaternionIsUnit( FrustumOrientation ) );
 
    // Load the box.
    XMVECTOR Center = XMLoadFloat3( &pVolumeA->Center );
    XMVECTOR Extents = XMLoadFloat3( &pVolumeA->Extents );
    XMVECTOR BoxOrientation = XMLoadFloat4( &pVolumeA->Orientation );
 
    XMASSERT( XMQuaternionIsUnit( BoxOrientation ) );
 
    // Transform the oriented box into the space of the frustum in order to 
    // minimize the number of transforms we have to do.
    Center = XMVector3InverseRotate( Center - Origin, FrustumOrientation );
    BoxOrientation = XMQuaternionMultiply( BoxOrientation, XMQuaternionConjugate( FrustumOrientation ) );
 
    // Set w of the center to one so we can dot4 with the plane.
    Center = XMVectorInsert( Center, XMVectorSplatOne(), 0, 0, 0, 0, 1);
 
    // Build the 3x3 rotation matrix that defines the box axes.
    XMMATRIX R = XMMatrixRotationQuaternion( BoxOrientation );
 
    // Check against each plane of the frustum.
    XMVECTOR Outside = XMVectorFalseInt();
    XMVECTOR InsideAll = XMVectorTrueInt();
    XMVECTOR CenterInsideAll = XMVectorTrueInt();
 
    for( INT i = 0; i < 6; i++ )
    {
        // Compute the distance to the center of the box.
        XMVECTOR Dist = XMVector4Dot( Center, Planes[i] );
 
        // Project the axes of the box onto the normal of the plane.  Half the
        // length of the projection (sometime called the "radius") is equal to
        // h(u) * abs(n dot b(u))) + h(v) * abs(n dot b(v)) + h(w) * abs(n dot b(w))
        // where h(i) are extents of the box, n is the plane normal, and b(i) are the 
        // axes of the box.
        XMVECTOR Radius = XMVector3Dot( Planes[i], R.r[0] );
        Radius = XMVectorSelect( Radius, XMVector3Dot( Planes[i], R.r[1] ), SelectY );
        Radius = XMVectorSelect( Radius, XMVector3Dot( Planes[i], R.r[2] ), SelectZ );
        Radius = XMVector3Dot( Extents, XMVectorAbs( Radius ) );
 
        // Outside the plane?
        Outside = XMVectorOrInt( Outside, XMVectorGreater( Dist, Radius ) );
 
        // Fully inside the plane?
        InsideAll = XMVectorAndInt( InsideAll, XMVectorLessOrEqual( Dist, -Radius ) );
 
        // Check if the center is inside the plane.
        CenterInsideAll = XMVectorAndInt( CenterInsideAll, XMVectorLessOrEqual( Dist, Zero ) );
    }
 
    // If the box is outside any of the planes it is outside. 
    if ( XMVector4EqualInt( Outside, XMVectorTrueInt() ) )
        return 0;
 
    // If the box is inside all planes it is fully inside.
    if ( XMVector4EqualInt( InsideAll, XMVectorTrueInt() ) )
        return 2;
 
    // If the center of the box is inside all planes and the box intersects 
    // one or more planes then it must intersect.
    if ( XMVector4EqualInt( CenterInsideAll, XMVectorTrueInt() ) )
        return 1;
 
    // Build the corners of the frustum.
    XMVECTOR RightTop = XMVectorSet( pVolumeB->RightSlope, pVolumeB->TopSlope, 1.0f, 0.0f );
    XMVECTOR RightBottom = XMVectorSet( pVolumeB->RightSlope, pVolumeB->BottomSlope, 1.0f, 0.0f );
    XMVECTOR LeftTop = XMVectorSet( pVolumeB->LeftSlope, pVolumeB->TopSlope, 1.0f, 0.0f );
    XMVECTOR LeftBottom = XMVectorSet( pVolumeB->LeftSlope, pVolumeB->BottomSlope, 1.0f, 0.0f );
    XMVECTOR Near = XMVectorReplicatePtr( &pVolumeB->Near );
    XMVECTOR Far = XMVectorReplicatePtr( &pVolumeB->Far );
 
    XMVECTOR Corners[8];
    Corners[0] = RightTop * Near;
    Corners[1] = RightBottom * Near;
    Corners[2] = LeftTop * Near;
    Corners[3] = LeftBottom * Near;
    Corners[4] = RightTop * Far;
    Corners[5] = RightBottom * Far;
    Corners[6] = LeftTop * Far;
    Corners[7] = LeftBottom * Far;
 
    // Test against box axes (3)
    {
        // Find the min/max values of the projection of the frustum onto each axis.
        XMVECTOR FrustumMin, FrustumMax;
 
        FrustumMin = XMVector3Dot( Corners[0], R.r[0] );
        FrustumMin = XMVectorSelect( FrustumMin, XMVector3Dot( Corners[0], R.r[1] ), SelectY );
        FrustumMin = XMVectorSelect( FrustumMin, XMVector3Dot( Corners[0], R.r[2] ), SelectZ );
        FrustumMax = FrustumMin;
 
        for( INT i = 1; i < 8; i++ )
        {
            XMVECTOR Temp = XMVector3Dot( Corners[i], R.r[0] );
            Temp = XMVectorSelect( Temp, XMVector3Dot( Corners[i], R.r[1] ), SelectY );
            Temp = XMVectorSelect( Temp, XMVector3Dot( Corners[i], R.r[2] ), SelectZ );
 
            FrustumMin = XMVectorMin( FrustumMin, Temp );
            FrustumMax = XMVectorMax( FrustumMax, Temp );
        }
 
        // Project the center of the box onto the axes.
        XMVECTOR BoxDist = XMVector3Dot( Center, R.r[0] );
        BoxDist = XMVectorSelect( BoxDist, XMVector3Dot( Center, R.r[1] ), SelectY );
        BoxDist = XMVectorSelect( BoxDist, XMVector3Dot( Center, R.r[2] ), SelectZ );
 
        // The projection of the box onto the axis is just its Center and Extents.
        // if (min > box_max || max < box_min) reject;
        XMVECTOR Result = XMVectorOrInt( XMVectorGreater( FrustumMin, BoxDist + Extents ),
                                          XMVectorLess( FrustumMax, BoxDist - Extents ) );
 
        if( XMVector3AnyTrue( Result ) )
            return 0;
    }
 
    // Test against edge/edge axes (3*6).
    XMVECTOR FrustumEdgeAxis[6];
 
    FrustumEdgeAxis[0] = RightTop;
    FrustumEdgeAxis[1] = RightBottom;
    FrustumEdgeAxis[2] = LeftTop;
    FrustumEdgeAxis[3] = LeftBottom;
    FrustumEdgeAxis[4] = RightTop - LeftTop;
    FrustumEdgeAxis[5] = LeftBottom - LeftTop;
 
    for( INT i = 0; i < 3; i++ )
    {
        for( INT j = 0; j < 6; j++ )
        {
            // Compute the axis we are going to test.
            XMVECTOR Axis = XMVector3Cross( R.r[i], FrustumEdgeAxis[j] );
 
            // Find the min/max values of the projection of the frustum onto the axis.
            XMVECTOR FrustumMin, FrustumMax;
 
            FrustumMin = FrustumMax = XMVector3Dot( Axis, Corners[0] );
 
            for( INT k = 1; k < 8; k++ )
            {
                XMVECTOR Temp = XMVector3Dot( Axis, Corners[k] );
                FrustumMin = XMVectorMin( FrustumMin, Temp );
                FrustumMax = XMVectorMax( FrustumMax, Temp );
            }
 
            // Project the center of the box onto the axis.
            XMVECTOR Dist = XMVector3Dot( Center, Axis );
 
            // Project the axes of the box onto the axis to find the "radius" of the box.
            XMVECTOR Radius = XMVector3Dot( Axis, R.r[0] );
            Radius = XMVectorSelect( Radius, XMVector3Dot( Axis, R.r[1] ), SelectY );
            Radius = XMVectorSelect( Radius, XMVector3Dot( Axis, R.r[2] ), SelectZ );
            Radius = XMVector3Dot( Extents, XMVectorAbs( Radius ) );
 
            // if (center > max + radius || center < min - radius) reject;
            Outside = XMVectorOrInt( Outside, XMVectorGreater( Dist, FrustumMax + Radius ) );
            Outside = XMVectorOrInt( Outside, XMVectorLess( Dist, FrustumMin - Radius ) );
        }
    }
 
    if ( XMVector4EqualInt( Outside, XMVectorTrueInt() ) )
        return 0;
 
    // If we did not find a separating plane then the box must intersect the frustum.
    return 1;
}
Edited by newtechnology

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newtechnology    1955

 

XNACollision does this for testing a AABB-frustum. It converts AABB to OBB and then does intersection tests.

Isn't this complex/slower compared to AABB-frustum test?

//-----------------------------------------------------------------------------
// Exact axis alinged box vs frustum test.  Constructs an oriented box and uses
// the oriented box vs frustum test.
//
// Return values: 0 = no intersection, 
//                1 = intersection, 
//                2 = box is completely inside frustum
//-----------------------------------------------------------------------------
INT IntersectAxisAlignedBoxFrustum( const AxisAlignedBox* pVolumeA, const Frustum* pVolumeB )
{
    XMASSERT( pVolumeA );
    XMASSERT( pVolumeB );
 
    // Make the axis aligned box oriented and do an OBB vs frustum test.
    OrientedBox BoxA;
 
    BoxA.Center = pVolumeA->Center;
    BoxA.Extents = pVolumeA->Extents;
    BoxA.Orientation.x = 0.0f;
    BoxA.Orientation.y = 0.0f;
    BoxA.Orientation.z = 0.0f;
    BoxA.Orientation.w = 1.0f;
 
    return IntersectOrientedBoxFrustum( &BoxA, pVolumeB );
}

 

 

Wouldn't this be faster than it?

bool Camera::isVisible(const AABB& box)const
{
// Test assumes frustum planes face inward.
 
D3DXVECTOR3 P;
D3DXVECTOR3 Q;
 
//      N  *Q                    *P
//      | /                     /
//      |/                     /
// -----/----- Plane     -----/----- Plane    
//     /                     / |
//    /                     /  |
//   *P                    *Q  N
//
// PQ forms diagonal most closely aligned with plane normal.
 
// For each frustum plane, find the box diagonal (there are four main
// diagonals that intersect the box center point) that points in the
// same direction as the normal along each axis (i.e., the diagonal 
// that is most aligned with the plane normal).  Then test if the box
// is in front of the plane or not.
for(int i = 0; i < 6; ++i)
{
// For each coordinate axis x, y, z...
for(int j = 0; j < 3; ++j)
{
// Make PQ point in the same direction as the plane normal on this axis.
if( mFrustumPlanes[i][j] >= 0.0f )
{
P[j] = box.minPt[j];
Q[j] = box.maxPt[j];
}
else 
{
P[j] = box.maxPt[j];
Q[j] = box.minPt[j];
}
}
 
// If box is in negative half space, it is behind the plane, and thus, completely
// outside the frustum.  Note that because PQ points roughly in the direction of the 
// plane normal, we can deduce that if Q is outside then P is also outside--thus we
// only need to test Q.
if( D3DXPlaneDotCoord(&mFrustumPlanes[i], &Q) < 0.0f  ) // outside
return false;
}
return true;
}

EDIT: Oops. With a mistake, instead of editing thread, I posted a new post.

Edited by newtechnology

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