Hi all !

I have a (hope not stupid) question....

Is it possible to wrap an image (using an image map texture I suppose)
around an object such a sphere in a way it is not distorted ?

POV-Ray docs says that tha texture is used as if "the object is carved from"
or "the texture is projected onto": is it possible to have POV-Ray to do
different ?

Thanx in advance

Paolo

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Paolo Bormida wrote:

> Hi all !
> I have a (hope not stupid) question....
> Is it possible to wrap an image (using an image map texture I suppose)
> around an object such a sphere in a way it is not distorted ?
>
> POV-Ray docs says that tha texture is used as if "the object is carved from"
> or "the texture is projected onto": is it possible to have POV-Ray to do
> different ?
>
> Thanx in advance
> Paolo

    Have you tried the map_type option?
There are several image mapping types
type 0 - planer, type 1- spherical and there is also
cylindrical, toroidal, and maybe more I have forgotten.

For spherical mapping you would describe it like this:

sphere{<0,0,0>,1
 pigment{
  image_map{ tga "image.tga" map_type 1 once interpolate 2}
   translate<-.5,-.5,-.5>
    scale 2 }}

This should I believe accomplish what you are looking for.

If you have any further questions feel free to ask.
K.tyler

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I'd add a small point of clarification.....

1. Any 2d->3d mapping will involve distortion for anything
   other than a planar object.... POV simply gives you some
   choice to which distortion you apply.
2. The "object carved from" text comes from the fact POV
   treats all textures as 3-dimensional fields -- the
   different mapping techniques are different methods of
   mapping 2-d space into 3-d space.  This is inherently different
   from surface->surface mapping techniques ("uv - mapping") employed
   by renderers with 2-d primitives.... POV doesn't use surface
   textures, only volume textures.

   For a comparison, Bryce 3d has both 2d and 3d textures,
   while Ray Dream has 2d textures only (I believe).

   POVTM ( http://www.twysted.net/ ) has a slope-dependent texture
   option for height fields.  Slope is an inherently 2-d concept...
   thus this repesents an extension beyond the POV texturing
   paradign.  But then, when grass grows on a mountainside,
   it doesn't grow inside the mountain, only on the surface --
   on mountain-like scales, it's 2d.

Dan


K. Tyler wrote:
> 
> Paolo Bormida wrote:
> 
> > Hi all !
> > I have a (hope not stupid) question....
> > Is it possible to wrap an image (using an image map texture I suppose)
> > around an object such a sphere in a way it is not distorted ?

>     Have you tried the map_type option?
> There are several image mapping types
> type 0 - planer, type 1- spherical and there is also
> cylindrical, toroidal, and maybe more I have forgotten.

That's all.

-- 
http://www.flash.net/~djconnel/

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I don't think this replies to the intention of the original question.
I understand it as :
[Is there a way to place turbulence on an image map ?]
To which I do not have an answer of the top of my head, but I don't think this
is possible right now. And if as I think it is not, it would really be a very
nice idea.

Cheers,
Al.


Dan Connelly wrote:

> I'd add a small point of clarification.....
>
> 1. Any 2d->3d mapping will involve distortion for anything
>    other than a planar object.... POV simply gives you some
>    choice to which distortion you apply.
> 2. The "object carved from" text comes from the fact POV
>    treats all textures as 3-dimensional fields -- the
>    different mapping techniques are different methods of
>    mapping 2-d space into 3-d space.  This is inherently different
>    from surface->surface mapping techniques ("uv - mapping") employed
>    by renderers with 2-d primitives.... POV doesn't use surface
>    textures, only volume textures.
>
>    For a comparison, Bryce 3d has both 2d and 3d textures,
>    while Ray Dream has 2d textures only (I believe).
>
>    POVTM ( http://www.twysted.net/ ) has a slope-dependent texture
>    option for height fields.  Slope is an inherently 2-d concept...
>    thus this repesents an extension beyond the POV texturing
>    paradign.  But then, when grass grows on a mountainside,
>    it doesn't grow inside the mountain, only on the surface --
>    on mountain-like scales, it's 2d.
>
> Dan
>
> K. Tyler wrote:
> >
> > Paolo Bormida wrote:
> >
> > > Hi all !
> > > I have a (hope not stupid) question....
> > > Is it possible to wrap an image (using an image map texture I suppose)
> > > around an object such a sphere in a way it is not distorted ?
>
> >     Have you tried the map_type option?
> > There are several image mapping types
> > type 0 - planer, type 1- spherical and there is also
> > cylindrical, toroidal, and maybe more I have forgotten.
>
> That's all.
>
> --
> http://www.flash.net/~djconnel/



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[Alain CULOS <ZAl### [at] bigfootcom>]
| [Is there a way to place turbulence on an image map ?]

Turbulence can be placed on all pigments. 
You could even do this in Pov-Ray2

I really wish people would take time to actually _READ_ the manual.
Most of the requested features are in there allready..

-- 
A penny for your thoughts.
Mine are more expensive.

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>Is it possible to wrap an image (using an image map texture I suppose)
>around an object such a sphere in a way it is not distorted ?
>

How do you mean: "without distortion".  What do you want to do ?

Frans

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Dan Connelly wrote in message <35B074E4.221C5112@flash.net>...
>I'd add a small point of clarification.....
Ok, thank you very much for it :-)

Anyway ....

How can we get, in POV,  an image map being mapped onto an object, as if the
image is on a sheet of paper and we use the sheet to carefully (no wrinkles)
wrap the object ?

Yes, I know in reality we'll have to fold (or cut) the paper to wrap it ....

To put it simply ... I would like to place the image map onto the object as
if it was a decal (those images printed on sheet of paper you damp with
water then slide onto model of cars, planes and the like)

Sorry, I really have problems to figure out how image map works :-((

Thanx again

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This is the "spherical mapping" type. 

Note: I put followup-to "povray.general" in the 
header.  This topic really should not be cross-posted
to all of these groups.

Dan

Paolo Bormida wrote:
> 

> How can we get, in POV,  an image map being mapped onto an object, as if the
> image is on a sheet of paper and we use the sheet to carefully (no wrinkles)
> wrap the object ?
> 
> Yes, I know in reality we'll have to fold (or cut) the paper to wrap it ....
> 
> To put it simply ... I would like to place the image map onto the object as
> if it was a decal (those images printed on sheet of paper you damp with
> water then slide onto model of cars, planes and the like)
> 
> Sorry, I really have problems to figure out how image map works :-((
> 
> Thanx again




-- 
http://www.flash.net/~djconnel/

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> [Alain CULOS <ZAl### [at] bigfootcom>]
> | [Is there a way to place turbulence on an image map ?]
>
> Turbulence can be placed on all pigments.
> You could even do this in Pov-Ray2
>
> I really wish people would take time to actually _READ_ the manual.
> Most of the requested features are in there allready..

Well, you will not believe me but I read it all and even made a
comprehensive review and comments (101 comments). That was on 3.01,
windows help file. But you know, people are not encyclopeadias, they
forget ...The nice thing about this news group is you do not always
have to look through the docs since others may know the topic in
question on the tip of their tongue, while they may not know other
things.


> A penny for your thoughts.
> Mine are more expensive.

Two pence for you to think about respecting others : even if the answer
seems obvious to you, it does not mean others are simply dumb or silly,
they may have more expensive thoughs themselves that prevents them from
spending too much time at reading the docs (I spent three months just
doing that on my spare time, that pretty much already) and not learn
the whole lot by heart like a poem.
I guess discussion is about helping each other, not shooting at each
other.

Cherio,
Al.

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To answer me, please take out the Z from my address.

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Paolo Bormida wrote:

> How can we get, in POV,  an image map being mapped onto an object, as if the
> image is on a sheet of paper and we use the sheet to carefully (no wrinkles)
> wrap the object ?
>
> Sorry, I really have problems to figure out how image map works :-((

Sorry I had misunderstood your first question (probably I was reading too fast).

What you are asking is only possible with simple objects so far : plane, sphere,
cylindre.
What you probably want is what is sometimes referred to as (u, v) mapping - this
does not exist in POV 3.02, I do not know about POV 3.1. I know there are some
custom compiles of POV out there on the net that are able to do (u, v) mapping
with some objects (not all), this includes bezier patches and/or triangle
meshes, but I don't remember which do what (I never tried them).

The standard POV 3.02 (or previous) image map is pretty simple :
1-planar mapping (default) imagine you have your image printed on paper and
imagine again this piece of paper is repeated to infinity on top of itself. Then
carve (sculpt) your object into that block of paper : that is what you get with
a planar mapping technique.
2-spherical : your piece of paper has been wrapped onto a sphere (like you want,
but it will only work like you want on a sphere). Then imagine a series of
spheres wrapping each over with the same image wrapped around (but scaled so
that all spheres look the same in the distance : what is up stays up, what is at
45 degrees, stays at 45 degrees, ...). Your object whatever it is is then carved
into this block of spheres.
3-cylindrical : same except the image is wrapped around a cylinder rather than a
sphere.

I hope this helps,
Al.

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