[Algorithms] transforming a plane

[Charles B. <cb...@cb...>]

Is there a fast way to transform a plane?

Right now I'm doing it by rotating the normal and tranforming
a point on the plane, then re-generating the 4d-vector form of
the plane.  It seems there should be a way to do it with a
single 4x4 matrix multiply in some funny coordinate space.

On a related note, is there a fast way to transform an
axis-aligned bounding box?  With an AABB defined by a 'min'
and a 'max', I'm doing this :

	// the min transformed :
	VECTOR3D vMinT;

	frXForm.XFormVector(vMinT,min);

	// the three edges transformed :
	VECTOR3D vx,vy,vz;

	vx = (max.x - min.x) * frXForm.Axis(X_AXIS);
	vy = (max.y - min.y) * frXForm.Axis(Y_AXIS);
	vz = (max.z - min.z) * frXForm.Axis(Z_AXIS);

	min.x = vMinT.x + min(vx.x,0) + min(vy.x,0) + min(vz.x,0);
	min.y = vMinT.y + min(vx.y,0) + min(vy.y,0) + min(vz.y,0);
	min.z = vMinT.z + min(vx.z,0) + min(vy.z,0) + min(vz.z,0);
	max.x = vMinT.x + max(vx.x,0) + max(vy.x,0) + max(vz.x,0);
	max.y = vMinT.y + max(vx.y,0) + max(vy.y,0) + max(vz.y,0);
	max.z = vMinT.z + max(vx.z,0) + max(vy.z,0) + max(vz.z,0);

Basically, transform the low corner (the 'min'), and then
transform the edges along x,y, and z.  I can't think of anything
better.




--------------------------------------
Charles Bloom           www.cbloom.com