Richard Borsheim <rbo### [at] shawca> wrote:
> This is standard practice when modelling for games. Certainly Direct3D
> supports it and correctly renders it (in my experience). It is an incredibly
> effective technique (as long as you don't look too closely :-) )

  Then how would you render clear glass (with highlights) with such engine?

> For example
> the holes punched through the side of the wheel supports in this image
> (http://www.amabilis.com/gallery/Alex%20Grigny%20de%20Castro%20-%20Sojourner
> %20-%20Large.jpg) would not be renderable with POVRay.

  Why not? There have been several mentions about image_pattern in this
thread. You can use it to get that effect.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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> Maybe you understand all this now, but the problem you were describing
> seemed to show that you did not before.

I think that I knew that (or should have), but didn't apply it to this
particular case. My thinking was "100% translucency=Non-existence".

> You didn't say whether or not a finish were being used, so
> that would be good to know, however you did say "specular image_maps".
That
> must mean you do have a finish set up.

I did have a finish set up. It works fine if there is no specular set.

> Anyway, back to the item in question. Fact is, I think all you can do is
> like Nathan suggested already. To map out the image via a texture not
> pigment. For POV-Ray that would be the way to go about that punch-through
as
> you called it. The technique you told of isn't something I know about but
I
> get the idea.

I think I understand, but I don't think this could be applied in this
particular case since the POVRay file is "generated" and that would require
some steps that would be akward.

The solution/work-around is to only use punch-through modelling on objects
that don't require specularity/reflection etc.

> Hope you don't take all the 'not a bug' stuff the wrong way. For instance,
> Warp was pointing out the obvious. Some people expect highlights on clear
> objects if specular or phong is specified in a finish, others don't.
> Likewise, to see reflections if reflection is set, or not. Reflection
> behaves this way too.

I completely understand the "not a bug" stuff. I'm a developer myself and
know the "feature vs. bug" issue well. I did try to phrase it politely (but
obviously failed). I guess I'll have to post a request for a new feature:
"100% translucency = non-existence". Though, I suppose not many "real"
POVRay users will be interested in such a feature.

> Well, have I beat this into the ground enough?  :-)

Yup. Good job! Thanks.

BTW anyone know why if you use atmosphere you need to have something behind
the atmosphere or the "visible light" is not visible? Should I post that
somewhere else?

Richard
PS Here is something rendered with POVRay and created with my program (3D
Canvas) that I thought was particularly nice:
http://www.train-sim.com/dcforum/User_files/3ccaa5291beb7bb4.jpg

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> > This is standard practice when modelling for games. Certainly Direct3D
> > supports it and correctly renders it (in my experience). It is an
incredibly
> > effective technique (as long as you don't look too closely :-) )
>
>   Then how would you render clear glass (with highlights) with such
engine?

You probably wouldn't, but it would depend on the engine. You might use a
high level of translucency (say 99%) for glass and have a special case for
100% translucent which means don't render it. I just did a little test with
the engine I use and it just makes the highlight proportional to the
translucency which of course makes it impossible to create glass (without
faking it)

> > For example
> > the holes punched through the side of the wheel supports in this image
> >
(http://www.amabilis.com/gallery/Alex%20Grigny%20de%20Castro%20-%20Sojourner
> > %20-%20Large.jpg) would not be renderable with POVRay.
>
>   Why not? There have been several mentions about image_pattern in this
> thread. You can use it to get that effect.

I read the posts in the wrong order. See my other post.

Richard

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in news:3d10c362$1@news.povray.org Richard Borsheim wrote:

> BTW anyone know why if you use atmosphere you need to have something
> behind the atmosphere or the "visible light" is not visible? Should I
> post that somewhere else?
> 

In the doc, section "6.9.1 Atmospheric Media", in the note.

Ingo

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"Richard Borsheim" <rbo### [at] shawca> wrote...
> I guess I'll have to post a request for a new feature:
> "100% translucency = non-existence". Though, I suppose not many "real"
> POVRay users will be interested in such a feature.

FYI, it probably won't ever get added.  It's generally not good practice to
have a "trigger value" like that.

The more likely feature to be added in the future is a "finish map" which
will allow the finish to be directly controlled by a pattern.  Until then, a
"texture map" (already mentioned) is the way you can achieve this result.
It would look something like this:

texture {
  image_pattern {
    <your image file>
    use_alpha // so that it uses the alpha (transparancy) channel
  }
  texture_map {
    [0.0 texture {<your image texture with highlight>} ]
    [1.0 texture {<clear, no-highlight texture>} ]
  }
}

-Nathan

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You know what I want? Aside from a finish_map, but that would solve this
problem?

I want the ability to specify a "transparency_map" for the entire texture,
separate from the pigment, normal, or finish. Something that tells how much
whatever's underneath shows through.

This would be a slightly easier way of mapping textures, only it would have
more advantages. For instance, right now, transparency can only be specified
in the pigment - but what if you have an image_map for your pigment, and
want to change the transparency? At the moment, I believe you'd have to
average the pigment with a transparent one. But with a transparency{} block
of some sort, you could do it more easily.

It would just be nice to have a way to influence the transparency of the
entire texture all at once.

 - Slime
[ http://www.slimeland.com/ ]

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Slime <slm### [at] slimelandcom> wrote:
> I want the ability to specify a "transparency_map" for the entire texture

  Does this suffice?

#macro TextureWithTransparency(OriginalTexture, TransparencyFunction)
  texture
  { function { TransparencyFunction(x,y,z) }
    texture_map
    { [0 OriginalTexture]
      [1 pigment { rgbt 1 }]
    }
  }
#end

// Example:
#declare MyTexture =
  texture
  { pigment
    { granite color_map { [0 rgb <.5,.3,.1>][1 rgb <1,.6,.3>] }
    }
  }

#declare Transparency = function { pattern { bozo scale .25 } }

camera { location <1,2,-5> look_at 0 angle 35 }
light_source { <100,200,-50>, 1 }
plane { y, -1 pigment { checker rgb 1, rgb .5 } }

sphere
{ 0,1
  TextureWithTransparency(MyTexture, Transparency)
}


-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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Hmm. Actually, that's not bad.

 - Slime
[ http://www.slimeland.com/ ]

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