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Errors-To: Princeton.EDU!cek
Remailed-Date: Mon Jun 28 07:34:26 EDT 1993
From: "Michael Schroeder (Inf4 - hiwi)" <immd4.informatik.uni-erlangen.de!mlschroe>
To: "Rayshade Distribution List" <cs.Princeton.EDU!rayshade-users>
Subject: sphere...


Uuuuugh, of cause the division by the radius of the sphere is
now obsolete. The patch should read:

*** sphere.c.orig	Sun Jun 27 21:53:08 1993
--- sphere.c	Mon Jun 28 13:32:55 1993
***************
*** 135,143 ****
  Sphere *sphere;
  Vector *pos, *nrm, *gnrm;
  {
! 	nrm->x = (pos->x - sphere->x) / sphere->r;
! 	nrm->y = (pos->y - sphere->y) / sphere->r;
! 	nrm->z = (pos->z - sphere->z) / sphere->r;
  	*gnrm = *nrm;
  	return FALSE;
  }
--- 135,148 ----
  Sphere *sphere;
  Vector *pos, *nrm, *gnrm;
  {
! 	nrm->x = pos->x - sphere->x;
! 	nrm->y = pos->y - sphere->y;
! 	nrm->z = pos->z - sphere->z;
! 	/*
! 	 * We cannot divide by sphere->r to normalize the vector 
! 	 * because of roundoff errors in the intersection calculation.
! 	 */
! 	VecNormalize(nrm);
  	*gnrm = *nrm;
  	return FALSE;
  }

Michael.

---------------------------------------------------------------
Michael Schroeder    mlschroe@faui43.informatik.uni-erlangen.de
main(a){while(a=~getchar())putchar(~a-1/(~(a|32)/13*2-11)*13);}

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