[Bf-cycles] Severe rendertimes

Brecht Van Lommel brechtvanlommel at pandora.be
Wed Dec 5 13:57:28 CET 2012


My best guess is that there is some specific geometry in the couch
that makes the BVH builder fail to create a good BVH tree (which would
be a bug). This might be something like zero area faces, or vertices
with invalid positions.

If diffuse bounces are enabled it's not really surprising that other
areas would be affected by this too. There is of course a maximum
number of bounces, but even one bounce could be very slow if the BVH
is built badly.


On Wed, Dec 5, 2012 at 1:36 PM, Andrew Price <andrew at blenderguru.com> wrote:
> Hey everyone,
> I noticed some bizarre behaviour with Cycles, and I'm wondering if anyone
> can explain what happened.
> I started with this mostly empty scene: http://i.imgur.com/I0s7F.png which
> rendered in 1min 30secs
> But then I added one high poly couch: http://imgur.com/Fecm2 which increased
> the render to 38mins.
> Now the strange part is that it rendered slow even in areas of the image
> without the couch (like the top left hand corner). The tiles that were
> completely away from the couch were now extremely slow to render, even
> though that area of the image was completely unaffected by the couch.
> I understand that light needs to bounce around the room, but doesn't Cycles
> have a bounce cutoff point or something?
> I'm using a very recent build of r52731.
> Thanks everyone!
> --
> Regards,
> Andrew Price
> http://www.blenderguru.com
> _______________________________________________
> Bf-cycles mailing list
> Bf-cycles at blender.org
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