cpca@iceman.jcu.oz (C Adams) (10/30/90)
Does anybody have C code for the Z buffer hidden surface algorithm. I would prefer code for the Amiga, but anything would be of help. Please send email. Thanks in advance. Colin Adams You need to have a woman, before you can have a Sun :-) Email Address - cpca@marlin.jcu.edu.au
jk87377@assari.tut.fi (Juhana Kouhia) (10/31/90)
In article <1157@iceman.jcu.oz> cpca@iceman.jcu.oz (C Adams) writes: >Does anybody have C code for the Z buffer hidden surface algorithm. >I would prefer code for the Amiga, but anything would be of >help. Hey, why is z-buffer based program hard to make by yourself? How many people out there have made z-buffer based program? Every year I read many wonderful articles from SIGGRAPH conference proceeding, from IEEE CG&A journal, but I have never implemented anything directly from papers. How common this is? Have anybody implemented for example Beam Tracer (1984), Path Tracer (1987), Spacetime Constraints (1988), REYES type hidden surface algorithm; dicing (1987), etc. etc.? How many of you think "Hey, nice algorithm... this I must do", when you see a new algorithm in the journal? Juhana Kouhia jk87377@tut.fi
AER6101@TECHNION.BITNET (11/02/90)
I am presently working with 3-D scene reconstruction from a sequence of images. The method I am using is based on corner matching between a pair of consecutive images. The output is the estimated depth at the corner pixels. The images are rendered by a perspective projection of 3-D blocks whose vertices are supplied by me as input to the program. However, the detected corners are not necessarily close to those vertices. In order to obtain a measurement of the accuracy of the algorithm I am using, the actual depth at that pixel is needed and I tried to recover it from the z-buffer. I thought that (my station is a SilliconGraphics 4D-GT) the z-buffer values (between 0 and 0x7fffff) were linearly mapped to the world z-coordinates between the closest and farthest planes used in the perspective projection procedure available in the Sillicon's graphic library. The results however don't match the above hypothesis. I tested the values of the z-buffer obtained when viewing a plane at a known depth and it was clear that the relation was not linear. Can someone enlighten me about how the z-buffer values are related to actual depth? I know there is a clipping transformation that transforms the perspective pyramid into a -1<x,y,z<1 cube, but perhaps I am missing something else. If anybody has an opinion or reference that could help me I would be very pleased to receive it in my E-mail (aer6101@technion.bitnet). I would summarize the received answers and post a message with the conclusions. Thanking you in advance, jacques-