CShake wrote:
> Good idea, but make sure to set max_trace_level so you don't get 
> infinite internal reflection.

Good point. Perhaps giving the large sphere the no_reflection (and 
no_shadow just to make things easier) would work too.

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CShake <cshake+pov### [at] gmailcom> wrote:
> Good idea, but make sure to set max_trace_level so you don't get 
> infinite internal reflection.

  When have you got infinite internal reflection?

-- 
                                                          - Warp

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David Given <dg### [at] cowlarkcom> wrote:
> On 04/01/10 19:59, Warp wrote:
> [...]
> >   If it is just a union, then make it an intersection CSG, but invert the
> > sphere. That way you will get a "hollow" moon surface which you can look
> > from the inside (with no overlapping surface pairs from the isosurface and
> > the sphere).

> Yeah, but it does involve a fair bit of fiddling with the model to make
> work. I'd like to avoid this if possible --- too many opportunities to
> break things!

  I don't think adding an 'inverse' keyword will break anything.

-- 
                                                          - Warp

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Kevin Wampler <wam### [at] uwashingtonedu> wrote:
> CShake wrote:
> > Good idea, but make sure to set max_trace_level so you don't get 
> > infinite internal reflection.

> Good point. Perhaps giving the large sphere the no_reflection (and 
> no_shadow just to make things easier) would work too.

  Don't listen to him. You can't get "infinite internal reflection" with
povray.

-- 
                                                          - Warp

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Warp wrote:
>   Don't listen to him. You can't get "infinite internal reflection" with
> povray.

I was more worried that the technique I proposed would make it 
impossible for any rays to ever get to the background, since they'd just 
be bounced by the sphere until the trace_limit was hit.  I don't think 
this would be a problem in David's case since all the rays will hit the 
moon anyway, but for a different scene it might make a difference.

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Warp wrote:
> CShake <cshake+pov### [at] gmailcom> wrote:
>> Good idea, but make sure to set max_trace_level so you don't get 
>> infinite internal reflection.
> 
>   When have you got infinite internal reflection?
> 
Hrm, never actually gotten it myself, but I've seen opposed mirrors 
create a lot of bounces and slow down rendering. If the exact center of 
this scene is sold, I guess it wouldn't be a problem, but if the object 
has any transparency I'd be worried about getting another reflection of 
the back side of it.

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Le 2010-01-05 20:59, David Given a écrit :

> Would it be feasible to use a plain orthographic camera imaging a plane,
> and then have a function pigment on the plain that used the trace()
> function to manually cast rays at the model? In other words, manually
> building my own camera with trace()? Would this actually work?
>
It can work, but the parsing will be prety slow.
The render itself should be relatively fast.


Alain

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Le 2010-01-05 22:23, CShake a écrit :
> Kevin Wampler wrote:
>> David Given wrote:
>>> Having thought about it some more, I think that what I'm looking for is
>>> a cross between an orthographic and spherical camera --- I want Povray
>>> to cast rays radially inwards from a spherical viewing surface towards
>>> the centre of my model. Does such a thing exist? If not, can I fake it?
>>
>> I haven't actually tried this, but perhaps you could put a spherical
>> camera at the center of your moon, put everything in your scene into
>> an object{...} construct with the no_image attribute, and then put a
>> large perfectly reflective sphere centered at your camera around the
>> scene?
> Good idea, but make sure to set max_trace_level so you don't get
> infinite internal reflection.

No such risk.
First, you go through the no_image object.
Next, you strike the large sphere.
Then, you get reflected back at your moon, whitch is NON-reflective.
You stop tracing there.

Then, you can't have more than 256 bounces... That,s hardly /infinite/.


Alain

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>>> Good idea, but make sure to set max_trace_level so you don't get 
>>> infinite internal reflection.
>>
>>   When have you got infinite internal reflection?
>>
> Hrm, never actually gotten it myself, but I've seen opposed mirrors create 
> a lot of bounces and slow down rendering. If the exact center of this 
> scene is sold, I guess it wouldn't be a problem, but if the object has any 
> transparency I'd be worried about getting another reflection of the back 
> side of it.

There was a bug in beta 34 that stalled some renders, it's fixed in beta 35.
If you have a hall of mirrors (HoM) effect, POV will color some
pixels black where they aren't reached before max_trace_level.
The default max_trace_level is only 10 bounces,
so stalling shouldn't be an issue.

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Warp schrieb:

>   Don't listen to him. You can't get "infinite internal reflection" with
> povray.

You could with 3.7.0 up until beta.34, in some semi-rare cases ;-)

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