[Soc-2009-dev] Raytrace api

André Pinto andresusanopinto at gmail.com
Sat May 30 01:04:59 CEST 2009

=== Week 1 report ===

==this week==
*Black dots - bug fix.

The simplest reproducible bug was:
http://andresp.no-ip.org/soc2009/blackdots.png <= you can see black dots on
edges connecting quads faces

The bug fixed: http://andresp.no-ip.org/soc2009/blackdots_fix.png <= this
scene previously gave many black dots.

I still wonder about the bug fix .. as the old code seemed more coeherent
with the comments and old code.

I took quite a while to fix the bug.. as there was no selftintersection
reported by code, but it was detecting intersections on the inner edge of a
quad face.
So i discarded many parts of code... after many/many hours.. i found that
makeraytree already receives triangles faces, so the bug was probably about
edges between faces.

*Link bvhkdop with raytrace
was done, it does the same results as octree on simples cases (image diff ==
But it looks something is wrong on more complex scenes.

==next week==
*See whats wrong with bvh tree
*Do instance support (that means adding a raytrace  object that "transforms"
between world space and local space).

still ahead of time considering the initial boost (before SoC starts)

2009/5/22 Matt Ebb <mattebb at gmail.com>

> On Sat, May 23, 2009 at 3:30 AM, André Pinto <andresusanopinto at gmail.com>
> wrote:
> > Hi,
> >
> > I probably wont be able to be online this sunday meeting.
> > Anyway my SoC plans for this first week are:
> >
> > ===comming week===
> >     *find the bug that makes some black dots.. before I only changed the
> > but it seems some bugs appeared.. I would like to have those sorted out
> > before continuing. I already spend some time trying. but its kinda hard
> to
> > debug it.
> What are the black dots? I don't know if it helps or not, or even if
> it's the same problem, but i've seen black dots/lines when rendering
> volumetrics, and I *think* its an issue in the raytrace code. When
> I've had these artifacts, I tried a whole bunch of things to try and
> debug - changing the octree size changed the appearance of the dots,
> triangulating my mesh helps to clean it up, and poking around in the
> code adding a large-ish offset to the ray start location (0.1 or
> something) helped too. From memory it happens when the ray fails to
> find an intersection, even though it's just being cast along the view
> vector with geometry behind. I wasn't able to figure out anything much
> more than that.
> Anyway, this may well be a problem in my code, or it may not be what
> you're experiencing. If it is the same thing though, it shows its not
> just in your code :)
> I think this is an example of the problem here, too:
> http://blenderartists.org/forum/showpost.php?p=1358587&postcount=651
> cheers
> Matt
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