public Q3BSPCollisionData Trace(Vector3 startPosition, Vector3 endPosition)
{
Q3BSPCollisionData cd = new Q3BSPCollisionData();
cd.startOutside = true;
cd.inSolid = false;
cd.ratio = 1.0f;
cd.startPosition = startPosition;
cd.endPosition = endPosition;
cd.collisionPoint = startPosition;
WalkNode(0, 0.0f, 1.0f, startPosition, endPosition, ref cd);
if (1.0f == cd.ratio)
{
cd.collisionPoint = endPosition;
}
else
{
cd.collisionPoint = startPosition + cd.ratio * (endPosition - startPosition);
}
return(cd);
}
private void WalkNode(int nodeIndex, float startRatio, float endRatio, Vector3 startPosition, Vector3 endPosition, ref Q3BSPCollisionData cd)
{
// Is this a leaf?
if (0 > nodeIndex)
{
Q3BSPLeaf leaf = leafs[-(nodeIndex + 1)];
for (int i = 0; i < leaf.LeafBrushCount; i++)
{
Q3BSPBrush brush = brushes[leafBrushes[leaf.StartLeafBrush + i]];
if (0 < brush.BrushSideCount &&
1 == (textureData[brush.TextureIndex].Contents & 1))
{
CheckBrush(ref brush, ref cd);
}
}
return;
}
// This is a node
Q3BSPNode thisNode = nodes[nodeIndex];
Plane thisPlane = planes[thisNode.Plane];
float startDistance = Vector3.Dot(startPosition, thisPlane.Normal) - thisPlane.D;
float endDistance = Vector3.Dot(endPosition, thisPlane.Normal) - thisPlane.D;
if (startDistance >= 0 && endDistance >= 0)
{
// Both points are in front
WalkNode(thisNode.Left, startRatio, endRatio, startPosition, endPosition, ref cd);
}
else if (startDistance < 0 && endDistance < 0)
{
WalkNode(thisNode.Right, startRatio, endRatio, startPosition, endPosition, ref cd);
}
else
{
// The line spans the splitting plane
int side = 0;
float fraction1 = 0.0f;
float fraction2 = 0.0f;
float middleFraction = 0.0f;
Vector3 middlePosition = new Vector3();
if (startDistance < endDistance)
{
side = 1;
float inverseDistance = 1.0f / (startDistance - endDistance);
fraction1 = (startDistance + Q3BSPConstants.epsilon) * inverseDistance;
fraction2 = (startDistance + Q3BSPConstants.epsilon) * inverseDistance;
}
else if (endDistance < startDistance)
{
side = 0;
float inverseDistance = 1.0f / (startDistance - endDistance);
fraction1 = (startDistance + Q3BSPConstants.epsilon) * inverseDistance;
fraction2 = (startDistance - Q3BSPConstants.epsilon) * inverseDistance;
}
else
{
side = 0;
fraction1 = 1.0f;
fraction2 = 0.0f;
}
if (fraction1 < 0.0f)
{
fraction1 = 0.0f;
}
else if (fraction1 > 1.0f)
{
fraction1 = 1.0f;
}
if (fraction2 < 0.0f)
{
fraction2 = 0.0f;
}
else if (fraction2 > 1.0f)
{
fraction2 = 1.0f;
}
middleFraction = startRatio + (endRatio - startRatio) * fraction1;
middlePosition = startPosition + fraction1 * (endPosition - startPosition);
int side1;
int side2;
if (0 == side)
{
side1 = thisNode.Left;
side2 = thisNode.Right;
}
else
{
side1 = thisNode.Right;
side2 = thisNode.Left;
}
WalkNode(side1, startRatio, middleFraction, startPosition, middlePosition, ref cd);
middleFraction = startRatio + (endRatio - startRatio) * fraction2;
middlePosition = startPosition + fraction2 * (endPosition - startPosition);
WalkNode(side2, middleFraction, endRatio, middlePosition, endPosition, ref cd);
}
}
private void CheckBrush(ref Q3BSPBrush brush, ref Q3BSPCollisionData cd)
{
float startFraction = -1.0f;
float endFraction = 1.0f;
bool startsOut = false;
bool endsOut = false;
for (int i = 0; i < brush.BrushSideCount; i++)
{
Q3BSPBrushSide brushSide = brushSides[brush.StartBrushSide + i];
Plane plane = planes[brushSide.PlaneIndex];
float startDistance = Vector3.Dot(cd.startPosition, plane.Normal) - plane.D;
float endDistance = Vector3.Dot(cd.endPosition, plane.Normal) - plane.D;
if (startDistance > 0)
{
startsOut = true;
}
if (endDistance > 0)
{
endsOut = true;
}
if (startDistance > 0 && endDistance > 0)
{
return;
}
if (startDistance <= 0 && endDistance <= 0)
{
continue;
}
if (startDistance > endDistance)
{
float fraction = (startDistance - Q3BSPConstants.epsilon) / (startDistance - endDistance);
if (fraction > startFraction)
{
startFraction = fraction;
}
}
else
{
float fraction = (startDistance + Q3BSPConstants.epsilon) / (startDistance - endDistance);
if (fraction < endFraction)
{
endFraction = fraction;
}
}
}
if (false == startsOut)
{
cd.startOutside = false;
if (false == endsOut)
{
cd.inSolid = true;
}
return;
}
if (startFraction < endFraction)
{
if (startFraction > -1.0f && startFraction < cd.ratio)
{
if (startFraction < 0)
{
startFraction = 0;
}
cd.ratio = startFraction;
}
}
}