// 
// Macros to generate "grown" objects.
// Growing an object expands the object by G along its normal.
//
// Available objects are GrowSphere, GrowBox, GrowTorus,
// GrowCylinder, and GrowCone.  Parameters are the same as for
// the standard object, with the addition of the G parameter.
//
// (c)2001 Michael D Johnson (aka Redbeard)
// redbeard@wv.adelphia.net
// 
// Free use for generating images is hearby granted.  Please
// do not sell, distribute, or modify without my permission.
//

#macro GrowSphere(P, R, G)
	sphere { P, R + G }
#end

// Assume P1 < P2
#macro GrowBox(P1, P2, G)
	box { P1 - G, P2 + G }
#end

#macro GrowTorus(R1, R2, G)
	torus { R1, R2 + G }
#end

#macro GrowCylinder(P1, P2, R, G)
	#local V = vnormalize(P2 - P1);
	cylinder { P1 - V * G, P2 + V * G, R + G }
#end

#macro GrowCone(P1, R1, P2, R2, G)
	#local H = VDist(P1, P2);
	#local B = R1 - R2;
	#local V = vnormalize(P2 - P1);
	#local N = G * B / H;
	#local M = vlength(<N, G, 0>);
	#local X1 = M + N;
	#local X2 = M - N;
	cone { P1 - V * G, R1 + X1, P2 + V * G, R2 + X2 }
#end