From theseas!fs.Princeton.EDU!cek Tue, 27 Apr 93 01:31:38 EET Received: by kriton.UUCP (V1.16/Amiga) id AA00000; Tue, 27 Apr 93 01:31:38 EET Received: by theseas.ntua.gr with UUCP; Tue, 27 Apr 93 00:37:23 +0300 Received: from mcsun.EU.net by pythia.ics.forth.gr via ITEnet with SMTP; id AA10288 (5.65c/FORTH-ICS-3.0-MHS-7.0); Tue, 27 Apr 1993 00:07:22 +0300 Received: by mcsun.EU.net via EUnet id AA17990 (5.65b/CWI-2.217); Mon, 26 Apr 1993 23:02:41 +0200 Received: from Princeton.EDU by relay2.UU.NET with SMTP (5.61/UUNET-internet-primary) id AA21952; Mon, 26 Apr 93 16:56:17 -0400 Received: from fs.Princeton.EDU by Princeton.EDU (5.65b/2.96/princeton) id AA00648; Mon, 26 Apr 93 16:53:48 -0400 Received: by fs.Princeton.EDU (4.1/1.105) id AA12696; Mon, 26 Apr 93 16:53:46 EDT Received: from faui45.informatik.uni-erlangen.de ([131.188.34.45]) by fs.Princeton.EDU (4.1/1.105) id AA12598; Mon, 26 Apr 93 16:52:59 EDT Received: from faui43.informatik.uni-erlangen.de by uni-erlangen.de with SMTP; id AA04018 (5.65c-5/7.3t-FAU); Mon, 26 Apr 1993 22:52:55 +0200 Received: by immd4.informatik.uni-erlangen.de; id AA28920 (5.65c-5/7.3m-FAU); Mon, 26 Apr 1993 22:52:53 +0200 Message-Id: <199304262052.AA28920@faui43.informatik.uni-erlangen.de> Date: Mon, 26 Apr 93 22:52:53 MDT X-Mailer: ELM [version 2.3 PL11] Errors-To: Princeton.EDU!cek Remailed-Date: Mon Apr 26 16:53:04 EDT 1993 From: "Michael Schroeder (Inf4 - hiwi)" To: "Rayshade Distribution List" Subject: blob and shadow bug Hello, there is a small bug in the blob intersection code that makes rayshade miss blob hits if mindist is not zero. This can happen if a ray to a light source hits a blob. Example: -------------------------------------------------- screen 120 100 light 1 directional -1 0 1 eyep 2 -10 3 lookp 0 0 0 surface glass diffuse 0 0 .5 transp 1 extinct .8 blob glass .2 1 1 0 2 0 box glass -.5 -2.5 -.5 .5 -1.5 .5 plane 0 0 -2 0 0 1 plane transp 1 -500 0 0 1 0 0 -------------------------------------------------- Patch: *** blob.c.orig Mon Apr 26 22:10:52 1993 --- blob.c Mon Apr 26 22:25:01 1993 *************** *** 250,256 **** /* * only interested in stuff in front of ray origin */ ! if (dmin < mindist) dmin = mindist; dmax = b + t; if (dmax > dmin) /* we have a valid Region */ { --- 250,256 ---- /* * only interested in stuff in front of ray origin */ ! if (dmin < mindist + EPSILON) dmin = mindist + EPSILON; dmax = b + t; if (dmax > dmin) /* we have a valid Region */ { Note that the fully transparent plane is necessary because rayshade doesn't handle a light source in a medium with nonzero extinction coefficient. (There is still the problem that the surfaces are not held on a stack, but that's another story...) What do you think? *** shadow.c.orig Mon Apr 26 22:30:52 1993 --- shadow.c Mon Apr 26 22:32:01 1993 *************** *** 233,238 **** --- 233,244 ---- */ hitlist.nodes = 0; } while (TraceRay(ray, &hitlist, totaldist, &s)); + if (prevsurf) { + if (prevsurf->statten != 1.) { + statten = pow(prevsurf->statten, dist - totaldist); + ColorScale(statten, res, &res); + } + } *result = res; 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);} ---------- Administrivia: rayshade-request@cs.princeton.edu Mailing list: rayshade-users@cs.princeton.edu