I have a scene containing various metal pipes, which I want to make into an
animation by moving the camera around the scene. (See
http://www.blueskylark.org/anim/cross4.wmv ) I have a couple of spotlights
which cast nice shadows, but I also want to model the reflections of the lights
on the shiny pipes ( texture { pigment { P_Brass4 } finish { F_MetalD  } } ),
which should give bright spots moving along the pipes as the points at which
the angles of incidence and reflection change.

A light source, being invisible, doesn't show up as a reflection. I then thought
of phong, but even phong 1 doesn't produce a noticeable effect, perhaps because
of the small diameter of the pipes. I then tried putting white disks behind the
spotlights, with additional very bright spotlights shining just on the disks.
This produced the required effect, but from some angles, the disks themselves
are visible, which I don't want.

Any ideas?

Regards - Philip

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pleriche <nomail@nomail> wrote:
> A light source, being invisible, doesn't show up as a reflection. I then thought
> of phong, but even phong 1 doesn't produce a noticeable effect, perhaps because
> of the small diameter of the pipes.

  Try modifying phong_size to make the highlight larger.

> I then tried putting white disks behind the
> spotlights, with additional very bright spotlights shining just on the disks.
> This produced the required effect, but from some angles, the disks themselves
> are visible, which I don't want.

  Rather than doing that, you could define a sphere as a looks_like object
for the light source (when it is defined in the looks_like block, the object
is automatically made shadowless). Define a high ambient finish for the
looks_like object.

-- 
                                                          - Warp

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> pleriche <nomail@nomail> wrote:
>> I then tried putting white disks behind the
>> spotlights, with additional very bright spotlights shining just on the 
>> disks.
>> This produced the required effect, but from some angles, the disks 
>> themselves
>> are visible, which I don't want.

You can also use the no_image and the no_shadow keyword on the the disks to 
prevent them from being visible directly. Then they should only be visible 
in reflections.

Regards,
Chris B.

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pleriche nous illumina en ce 2008-10-13 08:04 -->
> I have a scene containing various metal pipes, which I want to make into an
> animation by moving the camera around the scene. (See
> http://www.blueskylark.org/anim/cross4.wmv ) I have a couple of spotlights
> which cast nice shadows, but I also want to model the reflections of the lights
> on the shiny pipes ( texture { pigment { P_Brass4 } finish { F_MetalD  } } ),
> which should give bright spots moving along the pipes as the points at which
> the angles of incidence and reflection change.
> 
> A light source, being invisible, doesn't show up as a reflection. I then thought
> of phong, but even phong 1 doesn't produce a noticeable effect, perhaps because
> of the small diameter of the pipes. I then tried putting white disks behind the
> spotlights, with additional very bright spotlights shining just on the disks.
> This produced the required effect, but from some angles, the disks themselves
> are visible, which I don't want.
> 
> Any ideas?
> 
> Regards - Philip
> 
> 

I like the way it loops.

With phong, use a smaller value for phong_size to make the highlight broader.
If, instead, you use specular, a larger roughness value will broaden the highlight.

Instead of using additional spots to illuminate your disks, give them a high 
ambient value, like ambient 10 or more.
You can replace those disks with spheres located around the lights with the 
looks_like feature. In fact, you can model the whole spotlights that way if you 
want to.

Adding "no_image" render an object invisible by direct view, but visible in 
reflections.

-- 
Alain
-------------------------------------------------
If at first you don’t succeed, try again. Then quit. No use being a damn fool 
about it.

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"Chris B" <nom### [at] nomailcom> wrote:

> You can also use the no_image and the no_shadow keyword on the the disks to
> prevent them from being visible directly. Then they should only be visible
> in reflections.
>

I didn't know that technique would work; I'll have to give it a try!

Ken W.

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"Chris B" <nom### [at] nomailcom> wrote:
> > pleriche <nomail@nomail> wrote:
> >> I then tried putting white disks behind the
> >> spotlights, with additional very bright spotlights shining just on the
> >> disks.
> >> This produced the required effect, but from some angles, the disks
> >> themselves
> >> are visible, which I don't want.
>
> You can also use the no_image and the no_shadow keyword on the the disks to
> prevent them from being visible directly. Then they should only be visible
> in reflections.
>
> Regards,
> Chris B.

Thanks Chris - just what I needed!

Regards - Philip

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