> Martin <don### [at] onocom> wrote:
>> Hello!
>>
>> I was testing some texturing in meshes (because i'm very bad texturing
>> :P) exported from Wings 3D, when pov crashed while rendering
> 
> 
> 
> Duplicated it on my own!  Interesting, never seen this before.  Ok, tested an
> identical scene under 64-bit Windows XP SP2, 32-bit version of POV 3.6.2, and
> the scene renders just fine.  The crashes occurred in the 64-bit version 3.7 b34
> (also under Windows XP 64 SP2)
> 
> To trigger the crash seems to require a mesh with more than about 5000 vertices,
> I was able to get the crash with a 6000 vertex mesh.  The key seems to be
> something around the normals and the textures applied on a per vertex basis, as
> I exported and rendered the same mesh with:
> * uv_vectors and normal_vectors (crashed)
> * normal_vectors only (crashed)
> * uv_vectors only (completed successfully)
> * neither uv or normal vectors (completed successfully)
> (I ran meshes with only smoothed normals and a combination of smooth and hard
> edges to get the above using a max_trace_level of 1 )
> Then, with some fancy find-and-replacery, I removed the texture index after each
> face, removed the texture_list{}, then re-ran a crashing mesh with the texture
> applied to the entire mesh.  This allowed the render to complete successfully.
> 
> Here is where it gets weird:  While minimizing a scene for this, I found that
> changing the aspect ratio very slightly can sometimes prevent a crash.  That is,
> changing  right <4/3,0,0> to right <4.0001/3,0,0> allow renders that previously
> crashed to complete successfully.  I tried a few others, but could not find any
> sort of pattern - sometimes a given aspect ratio would crash, other times it
> would complete successfully.  Same with changing the output resolution - crashes
> became more random instead of certain.
> 
> A problem I ran into while trying to duplicate this is that... well, I couldn't
> always.  I wanted to (partially) rule out the exporter outputting improperly
> formatted meshes, so I exported some using the subdivision option and others
> smoothed manually.  The manually smoothed ones did not crash, but the mesh
> topography was slightly different (different number of vertexes, slightly
> different shape)  from running the smooth command twice, as opposed to telling
> it to subdivide for 2 steps (this isn't so strange, I suspect it is because the
> subdivide command tessellates into triangles first, but the mesh had
> quadrilaterals when I smoothed).
> 
> I hope this helps someone who has a better understanding of these things than I
> do. ;)
> 
> -Reactor
> 
> 

Ah, deep testing session :). Here is the scene file 
http://news.povray.org/4b1fb5ce%40news.povray.org

I just used the default settings to export the mesh. As you'll see in 
the .pov file i don't use uv_mapping. But there are uv_vectors all of 
them <0,0,0>... (<-candidate #1 :? I guess).

At first it had no subdivisions (and I think also crashed), but as the 
reflections were wavy, i tried to make 1 subdivision to see if the 
problem was solved (answer: no). Finaly I did the mesh again (the simple 
block) and it looks better (with 1 subdivision also).

It will be interesting to know if this error occurs also in linux or mac.

Martin.

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