bool intersection(Vector4 start1, Vector4 end1, Vector4 start2, Vector4 end2, Vector4 *out_intersection)
{
Vector4 dir1 = Vector4Subtract(end1, start1);
Vector4 dir2 = Vector4Subtract(end2, start2);
//считаем уравнения прямых проходящих через отрезки
float a1 = -dir1.y;
float b1 = +dir1.x;
float d1 = -(a1*start1.x + b1*start1.y);
float a2 = -dir2.y;
float b2 = +dir2.x;
float d2 = -(a2*start2.x + b2*start2.y);
//подставляем концы отрезков, для выяснения в каких полуплоскотях они
float seg1_line2_start = a2*start1.x + b2*start1.y + d2;
float seg1_line2_end = a2*end1.x + b2*end1.y + d2;
float seg2_line1_start = a1*start2.x + b1*start2.y + d1;
float seg2_line1_end = a1*end2.x + b1*end2.y + d1;
//если концы одного отрезка имеют один знак, значит он в одной полуплоскости и пересечения нет.
if (seg1_line2_start * seg1_line2_end >= 0 || seg2_line1_start * seg2_line1_end >= 0)
return false;
float u = seg1_line2_start / (seg1_line2_start - seg1_line2_end);
*out_intersection = Vector4Add(start1, Vector4MultiplyScalar(dir1, u));
return true;
}
void octGridGetVisibleNodes( tOctGrid const* pOctGrid,
CCamera const* pCamera,
std::vector<tOctNode const*>& aVisibleNodes )
{
// determine the extent of the frustum
tVector4 topLeftNear = { 9999.0f, -9999.0f, 9999.0f };
tVector4 bottomRightFar = { -9999.0f, 9999.0f, -9999.0f };
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mFarBottomLeft );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mFarBottomRight );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mFarTopLeft );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mFarTopRight );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mNearBottomLeft );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mNearBottomRight );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mNearTopLeft );
getExtent( &topLeftNear, &bottomRightFar, &pCamera->mNearTopRight );
tVector4 nodeSize =
{
pOctGrid->mDimension.fX / (float)pOctGrid->miNumNodesInDimension,
pOctGrid->mDimension.fY / (float)pOctGrid->miNumNodesInDimension,
pOctGrid->mDimension.fZ / (float)pOctGrid->miNumNodesInDimension,
1.0
};
tVector4 gridNearTopLeft =
{
-nodeSize.fX * (float)pOctGrid->miNumNodesInDimension * 0.5f,
nodeSize.fY * (float)pOctGrid->miNumNodesInDimension * 0.5f,
-nodeSize.fZ * (float)pOctGrid->miNumNodesInDimension * 0.5f,
1.0f
};
tVector4 gridFarBottomRight =
{
nodeSize.fX * (float)pOctGrid->miNumNodesInDimension * 0.5f,
-nodeSize.fY * (float)pOctGrid->miNumNodesInDimension * 0.5f,
nodeSize.fZ * (float)pOctGrid->miNumNodesInDimension * 0.5f,
1.0f
};
// get the octnode indices in the grid
float fLeft = topLeftNear.fX / nodeSize.fX;
float fRight = bottomRightFar.fX / nodeSize.fX;
float fTop = topLeftNear.fY / nodeSize.fY;
float fBottom = bottomRightFar.fY / nodeSize.fY;
float fNear = topLeftNear.fZ / nodeSize.fZ;
float fFar = bottomRightFar.fZ / nodeSize.fZ;
// X
int iLeft = (int)ceilf( fLeft );
int iRight = (int)ceilf( fRight );
// Y
int iTop = (int)ceilf( fTop );
int iBottom = (int)ceilf( fBottom );
// Z
int iNear = (int)ceilf( fNear );
int iFar = (int)ceilf( fFar );
// floor for sign correctness
if( fLeft < 0.0 )
{
iLeft = (int)floorf( fLeft );
}
if( fRight < 0.0 )
{
iRight = (int)floorf( fRight );
}
if( fTop < 0.0 )
{
iTop = (int)floorf( fTop );
}
if( fBottom < 0.0 )
{
iBottom = (int)floorf( fBottom );
}
if( fNear < 0.0 )
{
iNear = (int)floorf( fNear );
}
if( fFar < 0.0 )
{
iFar = (int)floorf( fFar );
}
// grid index extent
int iGridLeft = (int)floorf( gridNearTopLeft.fX / nodeSize.fX );
int iGridRight = (int)ceilf( gridFarBottomRight.fX / nodeSize.fX );
int iGridTop = (int)ceilf( gridNearTopLeft.fY / nodeSize.fY );
int iGridBottom = (int)ceilf( gridFarBottomRight.fY / nodeSize.fY );
int iGridNear = (int)floorf( gridNearTopLeft.fZ / nodeSize.fZ );
int iGridFar = (int)ceilf( gridFarBottomRight.fZ / nodeSize.fZ );
// clamp
if( iLeft < iGridLeft )
{
iLeft = iGridLeft;
}
if( iRight >= iGridRight )
{
iRight = iGridRight - 1;
}
if( iBottom < iGridBottom )
{
iBottom = iGridBottom;
}
if( iTop >= iGridTop )
{
iTop = iGridTop - 1;
}
if( iNear < iGridNear )
{
iNear = iGridNear;
}
if( iFar >= iGridFar )
{
iFar = iGridFar - 1;
}
int iNumNodes = pOctGrid->miNumNodesInDimension;
int iHalfNumNodes = iNumNodes >> 1;
// shift to (0, num nodes)
iLeft += iHalfNumNodes;
iRight += iHalfNumNodes;
iTop += iHalfNumNodes;
iBottom += iHalfNumNodes;
iNear += iHalfNumNodes;
iFar += iHalfNumNodes;
// check for nodes in boundary
tOctNode const* aNodes = pOctGrid->maNodes;
for( int iZ = iNear; iZ <= iFar; iZ++ )
{
for( int iY = iBottom; iY <= iTop; iY++ )
{
for( int iX = iLeft; iX <= iRight; iX++ )
{
int iIndex = iZ * iNumNodes * iNumNodes + iY * iNumNodes + iX;
tOctNode const* pOctNode = &aNodes[iIndex];
bool bInFrustum = pCamera->cubeInFrustum( pOctNode->mpCenter, pOctNode->mfSize );
if( bInFrustum )
{
aVisibleNodes.push_back( pOctNode );
//OUTPUT( "%d OCTNODE IN FRUSTUM ( %f, %f, %f )\n", (int)aVisibleNodes.size(), pOctNode->mpCenter->fX, pOctNode->mpCenter->fY, pOctNode->mpCenter->fZ );
}
} // for x = left to right
} // for y = bottom to top
} // for z = near to far
#if 0
aVisibleNodes.clear();
// camera direction
tVector4 const* pCamPos = pCamera->getPosition();
tVector4 const* pLookAt = pCamera->getLookAt();
tVector4 dir;
Vector4Subtract( &dir, pLookAt, pCamPos );
Vector4Normalize( &dir, &dir );
tVector4 const* aCenters = pOctGrid->maNodeCenters;
float fNodeSize = pOctGrid->maNodes[0].mfSize;
// brute force for now
for( int iZ = 0; iZ < iNumNodes; iZ++ )
{
for( int iY = 0; iY < iNumNodes; iY++ )
{
for( int iX = 0; iX < iNumNodes; iX++ )
{
bool bInFrustum = pCamera->cubeInFrustum( aCenters, fNodeSize );
++aCenters;
if( bInFrustum )
{
int iIndex = iZ * iNumNodes * iNumNodes + iY * iNumNodes + iX;
WTFASSERT2( iIndex < pOctGrid->miNumNodes, "nodes out of bounds while getting visible" );
aVisibleNodes.push_back( &pOctGrid->maNodes[iIndex] );
}
} // for x = 0 to num nodes
} // for y = 0 to num nodes
} // for z = 0 to num nodes
#endif // #if 0
}
