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Organization: Institute of Computer Science, 
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Date: Fri, 15 Jul 1994 13:55:01 +0200
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Reply-To: tmueller@ira.uka.de
Errors-To: rayshade-users-request@cs.Princeton.EDU
Remailed-Date: Mon Jul 18 03:28:54 EDT 1994
From: Thomas Mueller AKA Howie <tmueller@ira.uka.de>
To: rayshade-users@cs.Princeton.EDU
Subject: csg with more then 2 objects

Hi!

Finally I was so tired of writing those deeply nested csg specifications that
I have fixed the problem.  If you want this too, simply replace the function
CsgConvert in libray/libobj/csg.c with the code at the end of this mail.

The new version of CsgConvert transforms a construct like

union obj1 obj2 obj3 end

into

union union obj1 obj2 end obj3 end

in terms of internal data structures.

Thomas

----8<--------8<--------8<--------8<--------8<--------8<--------8<----
int
CsgConvert(csg, list)
Csg *csg;
Geom *list;
{
	static int OpenAdvised = FALSE;
	int prims = 0;

	if (!list || !list->next) {
		RLerror(RL_WARN, "CSG needs at least two objects.\n");
		return 0;
	}
	/*
	 * Things are put into lists backwards....
	 */
	csg->obj2 = list;
	if (!list->methods->closed && !OpenAdvised) {
	  RLerror(RL_ADVISE, "Performing CSG with non-closed object(s).\n");
	  OpenAdvised = TRUE;
	}
	prims += list->prims;
	list = list->next;
	while (list->next) {
	  csg->obj1 = GeomCsgCreate(csg->operator);
	  csg = (Csg*)csg->obj1->obj;
	  csg->obj2 = list;
	  if (!list->methods->closed && !OpenAdvised) {
	    RLerror(RL_ADVISE, "Performing CSG with non-closed object(s).\n");
	    OpenAdvised = TRUE;
	  }
	  prims += list->prims;
	  list = list->next;
	}
	csg->obj1 = list;
	if (!list->methods->closed && !OpenAdvised) {
	  RLerror(RL_ADVISE, "Performing CSG with non-closed object(s).\n");
	  OpenAdvised = TRUE;
	}
	prims += list->prims;

	return prims;
}

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