Severi Salminen wrote:
> Still don't know what was the reason.

Overheating? :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

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On 27-Jan-09 9:03, Severi Salminen wrote:
> andrel wrote:
> 
>> use blender, wings3d or something like that and export a few basic
>> shapes as obj
> 
> Thanks, that was a good idea! I exported and imported the Blender monkey
> model (in .obj) and here is the result:
> 
> http://www.saunalahti.fi/~sevesalm/ssRay/ShowImage.php?img=27
> 
> w00t, it works :D It is slow but looks to render quite properly.
> However, my system crashed at 7am for some reason (blinking keyboard
> leds - kernel panic, maybe?). Still don't know what was the reason.

What happened here?

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Attachments:
Download 'kuva27.jpg' (7 KB)

Preview of image 'kuva27.jpg'

On 27-Jan-09 9:23, scott wrote:
>>> Another advantage of OBJ is that it support quads. I think 3DS only 
>>> supports
>>> triangles?
>>
>>  Rendering a (non-rectangular) textured quad is not an unambiguous 
>> process.
>> How do you do that? Dividing it into two triangles will get you a 
>> texturing
>> artifact.
> 
> To be clearer, there is no expected or obvious way how the inside of a 
> quad should be textured given the four vertex texture coordinates.  
> Converting to two triangles does it one way, but there are other 
> possibilities.  In practise every modeller and renderer will convert it 
> to two triangles, so I guess that can be thought of the "standard" way.

I normally cut them in 4 (using the center of mass as a fifth vertex) 
that at least gives a unique division.

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> What happened here?

Good question. I wondered the same and that is actually caused by
Blender. ssRay only knows about triangles so I let Blender triangulate
all the quads. And it seems it did poor job... The same problems show in
Blender when I import the exported mesh back. But anyway, it should be
rendered correctly - only the model is a bit broken.

SS

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Severi Salminen escreveu:
>> What happened here?
> 
> Good question. I wondered the same and that is actually caused by
> Blender. ssRay only knows about triangles so I let Blender triangulate
> all the quads. And it seems it did poor job... The same problems show in
> Blender when I import the exported mesh back. But anyway, it should be
> rendered correctly - only the model is a bit broken.

The exporter doesn`t seem ok, then.  But that looks weirdly like a 
glitch with the normal calculations.  In Blender, you may try to do, in 
edit mode (tab):

1) convert all to triangles CTRL+T
2) recalculate the normals CTRL+N
3) export

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nemesis wrote:

> The exporter doesn`t seem ok, then.  But that looks weirdly like a
> glitch with the normal calculations.  In Blender, you may try to do, in
> edit mode (tab):
> 
> 1) convert all to triangles CTRL+T

I tried this and the error is already shown here. You can try it
yourself. Just look near eye brow after triangulation and the problem is
there. It seems that blender triangulates the quad incorrectly. It
should split it the other way.

> 2) recalculate the normals CTRL+N

I actually calculate the normals in ssRay. But should be just fine. By
inverting the normals, you' see a totally black monkey.

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nemesis wrote:

> The exporter doesn`t seem ok, then.  But that looks weirdly like a
> glitch with the normal calculations.  In Blender, you may try to do, in
> edit mode (tab):

Oh, and the problem is also that how should a face made from 4 vertices
which DON'T lie on the same plane look like? It is ambiguous.

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Severi Salminen escreveu:
> nemesis wrote:
> 
>> The exporter doesn`t seem ok, then.  But that looks weirdly like a
>> glitch with the normal calculations.  In Blender, you may try to do, in
>> edit mode (tab):
> 
> Oh, and the problem is also that how should a face made from 4 vertices
> which DON'T lie on the same plane look like? It is ambiguous.

I saw what you mean.  Then again, I'm used to the quad-only approach as 
required by box-modelling with subsurface division so this was quite 
never a problem to me.

In my naive view I would expect, though, that Blender would convert the 
triangles to lie in the same plane as the parent quads they come from. 
It isn't so, however, as seen in the ears and eyebrows...

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Warp <war### [at] tagpovrayorg> wrote:
> > In
> > practise every modeller and renderer will convert it to two triangles, so I
> > guess that can be thought of the "standard" way.
>
>   It might be the "standard" way, but it produces an incorrect texturing
> (with non-rectangular quads). The texture would require a non-linear
> transformation to be rendered correctly on such a quad.

So what do you suggest? Use .3ds instead of .obj file format because then you
can't handle quads at all, and the problem is somebody else's?

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nemesis <nam### [at] gmailcom> wrote:
> Nice too see a renderer built from scratch

Yeah - gives me itches in the fingers to go and try as well... again ;)

Last time I tried, I didn't get further than opaque uniformly colored planes,
spheres and a few simple transformations (which happened to use the wrong math
for shading ;)) And I did have plenty of spare time back then...

Very impressive results!

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