POV-Ray : Newsgroups : povray.programming : Several blob bugs (job000189) : Re: Several blob bugs (job000189) Server Time
6 Oct 2024 14:37:16 EDT (-0400)
  Re: Several blob bugs (job000189)  
From: Massimo Valentini
Date: 26 Oct 2002 06:15:39
Message: <3dba6b4b@news.povray.org>
"Slime" ha scritto 
: > I think to have found a little error in the file blob.cpp
: 
: 
: Wow, this is a complicated post. While I may be able to understand it if I
: slowly read all the way through it, would you care to give a simplified
: explanation of what was wrong in the code? Was it just a typo? Was something
: assumed to work that didn't? Just out of curiosity.

You may call it a typo. I think someone trying to simplify a computation
(division -> multiplication of the reciprocal or similar) made a double
division instead of a division and a multiplication, so three numbers 
ended up to be a fourth of their correct value.

The lines to modify are around 545 in the file blob.cpp (if you need more 
context, look at my previous post or the bug report). 
Substitute for example:

dk[2] = newcoeffs[4] + 0.50 * (newcoeffs[3] + newcoeffs[2] / 12.0);
dk[3] = newcoeffs[4] + 0.50 * (0.375 * newcoeffs[3] + newcoeffs[2] + 0.125 *
newcoeffs[1]);

with:

dk[2] = newcoeffs[4] + 0.50 * (newcoeffs[3] + newcoeffs[2] / 3.0);
dk[3] = newcoeffs[4] + 0.50 * (1.5 * newcoeffs[3] + newcoeffs[2] + 0.5 *
newcoeffs[1]);


: And was this the only bug in the blob code? That'd be nice if it were =)
: 

It is the only one I found. But it does not affect other scenes 
reported as bugs.

Massimo


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