I'm going mad!
I want to use blender to model some mesh, and then render it using pov.
Now i've tried to export it using wavefront, using povanim, using a lot of
tools but every time i get awful results, especially with the normals.

For example: consider a cylinder. I've made it in blender, i've smoothed,
and render it. It goes well.
Now, every exports i made, the results is like this:

http://img370.imageshack.us/img370/6343/mainfg4.jpg

Something is a little better, something not, anyway there's always an ugly
black area away from the light source.

Any Idea? How can i use shaded mesh from blender to pov?

Thanks.

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PdG nous apporta ses lumieres en ce 2007/07/15 07:45:
> I'm going mad!
> I want to use blender to model some mesh, and then render it using pov.
> Now i've tried to export it using wavefront, using povanim, using a lot of
> tools but every time i get awful results, especially with the normals.
> 
> For example: consider a cylinder. I've made it in blender, i've smoothed,
> and render it. It goes well.
> Now, every exports i made, the results is like this:
> 
> http://img370.imageshack.us/img370/6343/mainfg4.jpg
> 
> Something is a little better, something not, anyway there's always an ugly
> black area away from the light source.
> 
> Any Idea? How can i use shaded mesh from blender to pov?
> 
> Thanks.
Maybe some normals are pointing "inside" the object instead of outward.
Any luck if you don't use shaded mesh?
Did you try PoseRay?

Anyway, unless your mesh is very fine, there will be some artefacts near the 
terminator, where the incident light comes at a grazing angle.
You can minimize that by carefully placing the light or by using some small 
rotation of the mesh.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you've tried rendering hair with 
each strand as an object.
Quietly Watching

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PdG <pdg### [at] intermerdagmailcom> wrote:
> http://img370.imageshack.us/img370/6343/mainfg4.jpg

  It's difficult to say anything from that image. Could you create a better
image which shows clearly the problem?

-- 
                                                          - Warp

Post a reply to this message

Il 15 Jul 2007 11:32:06 -0400, Warp ha scritto:

> PdG <pdg### [at] intermerdagmailcom> wrote:
>> http://img370.imageshack.us/img370/6343/mainfg4.jpg
> 
>   It's difficult to say anything from that image. Could you create a better
> image which shows clearly the problem?

Look here

http://img68.imageshack.us/img68/7717/diokvu6.jpg

two renders of the same object: the left made with povray, the right made
with blender... left has a ugly and wrong black area.. i've used only a
spot light, there's noting that drop shadows so why that area is so black?

Post a reply to this message

PdG nous apporta ses lumieres en ce 2007/07/15 12:21:
> Il 15 Jul 2007 11:32:06 -0400, Warp ha scritto:
> 
>> PdG <pdg### [at] intermerdagmailcom> wrote:
>>> http://img370.imageshack.us/img370/6343/mainfg4.jpg
>>   It's difficult to say anything from that image. Could you create a better
>> image which shows clearly the problem?
> 
> Look here
> 
> http://img68.imageshack.us/img68/7717/diokvu6.jpg
> 
> two renders of the same object: the left made with povray, the right made
> with blender... left has a ugly and wrong black area.. i've used only a
> spot light, there's noting that drop shadows so why that area is so black?
The end of the cylinder looks as black in one view as in the other.
It looks like the light source is very close to the object, making the far end 
receiving light at a very shalow angle.

-- 
Alain
-------------------------------------------------
Keep your eyes wide open before marriage, half shut afterwards.
Benjamin Franklin

Post a reply to this message

PdG <pdg### [at] intermerdagmailcom> wrote:
> http://img68.imageshack.us/img68/7717/diokvu6.jpg

  I see no relevant difference in the two images.

-- 
                                                          - Warp

Post a reply to this message

Il Sun, 15 Jul 2007 11:15:05 -0400, Alain ha scritto:


> Maybe some normals are pointing "inside" the object instead of outward.
> Any luck if you don't use shaded mesh?

if i use solid mesh it seems to works, but i need shaded mesh..

i've flipped the normals, but...

http://img377.imageshack.us/img377/8940/uglycc7.jpg

Post a reply to this message

Il Sun, 15 Jul 2007 13:19:35 -0400, Alain ha scritto:

>> http://img68.imageshack.us/img68/7717/diokvu6.jpg
>> 
>> two renders of the same object: the left made with povray, the right made
>> with blender... left has a ugly and wrong black area.. i've used only a
>> spot light, there's noting that drop shadows so why that area is so black?
> The end of the cylinder looks as black in one view as in the other.
> It looks like the light source is very close to the object, making the far end 
> receiving light at a very shalow angle.

i've putted the light far.. and the effects looks like a spot light, not a
point light.. the cylinder become black with no smooth.. like if the lights
stops after these pixels.

Anyway, here the source.

// File produced by AccuTrans 3D

#version 3.5;

global_settings { assumed_gamma 2.2 }

camera {
  location <1.0, 1.5, -12.0>
  look_at <0, 0, 0>
}

light_source { <0, 12.0, -30.0> color rgb<1, 1, 1> }

light_source {
  <0, 0, -24.0>
  color rgb<1, 1, 1>
  spotlight
  radius 150
  falloff 20
  tightness 10
  point_at <0, 0, 0>
}

background { color rgb<0.5765, 0.6863, 0.8549> }

// Layer: _null_
//  
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Post a reply to this message

Il 15 Jul 2007 13:26:24 -0400, Warp ha scritto:

> PdG <pdg### [at] intermerdagmailcom> wrote:
>> http://img68.imageshack.us/img68/7717/diokvu6.jpg
> 
>   I see no relevant difference in the two images.

the first has an ireealistic black zone, the second has a smoot gradient
from light to dark, and if i use a cylinder statement instead of the mesh,
pov renders it like blender.

Post a reply to this message

The faces are inverted, normals pointing inward,
they should point outward.

Post a reply to this message

"Tim Attwood" <tim### [at] comcastnet> wrote:
> The faces are inverted, normals pointing inward,
> they should point outward.

hmmm. i've tried to swap the normals, but the black area remains.

Post a reply to this message

IMO you hit the shadow line artifact:
http://www.povray.org/documentation/view/3.6.1/193/

If you subdivide your mesh the shadow line artifact should move further out
and occur in a deeper grey area, but you won't get rid of it.

Post a reply to this message

PdG <pdg### [at] intermerdagmailcom> wrote:
> the first has an ireealistic black zone, the second has a smoot gradient
> from light to dark, and if i use a cylinder statement instead of the mesh,
> pov renders it like blender.

  I still see no difference in the images.

  Anyways, just out of curiosity, what happens if you speficy "no_shadow"
in the mesh when you render it with povray?

-- 
                                                          - Warp

Post a reply to this message

Il 16 Jul 2007 06:07:43 -0400, Warp ha scritto:

> PdG <pdg### [at] intermerdagmailcom> wrote:
>> the first has an ireealistic black zone, the second has a smoot gradient
>> from light to dark, and if i use a cylinder statement instead of the mesh,
>> pov renders it like blender.
> 
>   I still see no difference in the images.

i think you've some problem with the contrast on your monitor :)
 
>   Anyways, just out of curiosity, what happens if you speficy "no_shadow"
> in the mesh when you render it with povray?

i'll try, but i think it's the same: there's no other object in the scene,
so there's nothing that could make shadows over the cylinder.

Post a reply to this message

PdG <pdg### [at] intermerdagmailcom> wrote:
> >   Anyways, just out of curiosity, what happens if you speficy "no_shadow"
> > in the mesh when you render it with povray?

> i'll try, but i think it's the same: there's no other object in the scene,
> so there's nothing that could make shadows over the cylinder.

  Yes, there is: The cylinder itself.

-- 
                                                          - Warp

Post a reply to this message

Blender isn't my prefered tool...
I think you need to tell it to export
the normals and to calculate them at
high quality in the export dialog.
(Blender ignores normals by default)

Post a reply to this message

PdG <pdg### [at] INTERMERDAgmailcom> wrote:
> if i use a cylinder statement instead of the mesh,

good thing you've seen the light! :)

really, is there any reason for using a gigantic mesh to represent a
cylinder when the builtin pov cylinder is much more reasonable and better
looking?

Post a reply to this message

Il Wed, 18 Jul 2007 10:02:18 EDT, nemesis ha scritto:

> PdG <pdg### [at] INTERMERDAgmailcom> wrote:
>> if i use a cylinder statement instead of the mesh,
> 
> good thing you've seen the light! :)
> 
> really, is there any reason for using a gigantic mesh to represent a
> cylinder when the builtin pov cylinder is much more reasonable and better
> looking?

the cylinder is only an example, i wonder if the cylinder makes all these
problems, a more complex mesh could have more?

Post a reply to this message

PdG <pdg### [at] intermerdagmailcom> wrote:
> >   Anyways, just out of curiosity, what happens if you speficy "no_shadow"
> > in the mesh when you render it with povray?

> i'll try

  So what happened?

-- 
                                                          - Warp

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PdG <pdg### [at] INTERMERDAgmailcom> wrote:
> I'm going mad!
> I want to use blender to model some mesh, and then render it using pov.
> Now i've tried to export it using wavefront, using povanim, using a lot of
> tools but every time i get awful results, especially with the normals.
>
> For example: consider a cylinder. I've made it in blender, i've smoothed,
> and render it. It goes well.
> Now, every exports i made, the results is like this:
>
> http://img370.imageshack.us/img370/6343/mainfg4.jpg
>
> Something is a little better, something not, anyway there's always an ugly
> black area away from the light source.
>
> Any Idea? How can i use shaded mesh from blender to pov?
>
> Thanks.

I've had a look at this and deconstructed the mesh.
First of all, the normals all point inward, which isn't such a big deal, as
they all point inward, not just some.

What is causing your problem though is the normals for the sides are not
normal to the cylinder, they are oriented as if there is a smooth
transition from the sides to the cap instead of being a sharp edge.  This
causes POV to treat the mesh as being curved more like a sphere and shades
it as such.  I don't use Blender, so I don't know how exporting works, but
you need to limit the angle at which the normals are smoothed for, so the
side meshes are smoothed around the cylinder, but not up and down the
cylinder.

-tgq

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"Trevor G Quayle" <Tin### [at] hotmailcom> schreef in bericht 
news:web.469e7741dedc19f1c150d4c10@news.povray.org...
> PdG <pdg### [at] INTERMERDAgmailcom> wrote:

>> For example: consider a cylinder. I've made it in blender, i've smoothed,
>> and render it. It goes well.
>> Now, every exports i made, the results is like this:
>>
>
> I've had a look at this and deconstructed the mesh.
> First of all, the normals all point inward, which isn't such a big deal, 
> as
> they all point inward, not just some.
>
> What is causing your problem though is the normals for the sides are not
> normal to the cylinder, they are oriented as if there is a smooth
> transition from the sides to the cap instead of being a sharp edge.  This
> causes POV to treat the mesh as being curved more like a sphere and shades
> it as such.  I don't use Blender, so I don't know how exporting works, but
> you need to limit the angle at which the normals are smoothed for, so the
> side meshes are smoothed around the cylinder, but not up and down the
> cylinder.
>

I translated PdG's cylinder (through Poseray) to Silo and come to the same 
conclusion concerning the normals' orientation inward. That should be easy 
to correct.

However, I think that the important keyword that PdG has used in his initial 
message is: "i've smoothed".
Smoothing (or subdividing) is the culprit here. What you can do in Silo for 
instance, is to "crease" the edges of the cylinder so that the shape remains 
the same. Otherwise, the cylinder will turn into a spherical object the more 
you smooth or subdivide. I suppose now that something like edge creasing 
should be done in Blender before exporting to POV-Ray.

Thomas

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