There's an example of it's use in the Patterns.htm file which is packaged with
MegaPOV patch.
It's basically a texture_map using a image as guidelines for the texture index.

Bob

"Fabian Brau" <fab### [at] umhacbe> wrote in message
news:388F30B7.B024EBDD@umh.ac.be...
|
| > > someone can tell me the difference between image_pattern and
| > > material_map? What can image_pattern do that material_map cannot?
| > > A simple example would be cool :)
| > >
| > > Thanks
| > >
| > > Fabian.
| >
| > That was the very first question asked in this group when it was new.
| > I know because I asked it :)
| >
| >  The answer that Nathan gave me was -
| >
| > This was made for Thomas Baier for use with 3DS to POV conversions.  Let's
| > say you have two textures, and you want to use a black and white image
| > to fade between the two textures.  Now lets say all you have to work with
| > is material_map.  That would be a lot of work.  If you only wanted to use
| > two textures (no fading between), that would be easy, but since material_map
| > uses indices and single textures, fading would be very difficult and you'd
| > have a lot of "average{ texture_map { [0.5 t1] [0.4 t2] }}" statements.
| > You could put it in a while loop, but that would still be a lot of extra
| > work.
| >
| > Now, on the other hand, if you have image_pattern, you can use texture_map
| > instead of material_map, and just use the image as your image_pattern.
| > Simple.  Fast.  Saves memory (no need for 256 textures for those 256
| > shades of grey).
|
| Yes but one can use a gif with only 2 color define in the palette.
| But I feel that I don't understand yet this feature. I certainly need
| an example to see the advantage of this :)
|
| Thanks!
|
| Fabian.

Post a reply to this message

Sorry, I think I see what you're getting at and I didn't before.  If I
understand it correctly a 'material_map' does not allow for manipulation of the
indices the way 'image_pattern' does.
You can specify a [value texture] format instead of just list textures out 0 to
255.

#declare IPp=
  texture {
    image_pattern { tga "belinda.tga" use_alpha}
    texture_map {
      [0 pigment {rgb <1,0,0>} ] // index 0
      [.5 pigment {rgb <0,1,0>} ] // index 127
      [1 pigment {rgb <0,0,1>} ] // index 255
    } translate -.5 scale 1.5  // transformations
  }

Where as 'material_map' goes like this:

#declare IPm=
texture {
 material_map { tga "belinda.tga"
  texture { pigment {rgb <1,0,0>}} // index 0
  texture { pigment {rgb <0,1,0>}} // index 1
  texture { pigment {rgb <0,0,1>}} // index 2
 }}

That is if I understand any of it right.  You can include image_patterns inside
of image patterns apparently (nesting), material_maps don't seem to be capable
of that.

Bob

Post a reply to this message

On Wed, 26 Jan 2000 14:10:47 -0600, Bob Hughes wrote:
>Sorry, I think I see what you're getting at and I didn't before.  If I
>understand it correctly a 'material_map' does not allow for manipulation of the
>indices the way 'image_pattern' does.
>You can specify a [value texture] format instead of just list textures out 0 to
>255.

The other difference is that it fades from one texture to another if it gets
an intermediate index.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

Post a reply to this message

Fabian Brau <fab### [at] umhacbe> wrote...
> Hello,
>
> someone can tell me the difference between image_pattern and
> material_map? What can image_pattern do that material_map cannot?
> A simple example would be cool :)
>

Advantages of image_pattern:

1) it is not limited to textures; it can be used directly with normals and
pigments

2) it can provide more than 256 entries

3) it fades between entries (especially useful when you have fewer than 256)

4) it can be nested

5) it follows a more standard format (like most other patterns), unlike
material_map, which is specialized

6) interpolation of the bitmap works better (see documentation on
material_map for an explanation of why interpolation is not effective with
material_maps)


-Nathan

Post a reply to this message

This gets edited into the patterns.htm file I have here immediately, thanks
Nathan.
Didn't know about the "more than 256" thing.  Great, but I don't see how it
could.  After all, if there's only a 256 color palette or one 8-bit plane of a
24bit image how does it apply textures to other than those specific areas of a
image then?  A kind of interpolation?

Bob

"Nathan Kopp" <Nat### [at] Koppcom> wrote in message
news:388faaaa@news.povray.org...
|
| Advantages of image_pattern:
|
| 1) it is not limited to textures; it can be used directly with normals and
| pigments
|
| 2) it can provide more than 256 entries
|
| 3) it fades between entries (especially useful when you have fewer than 256)
|
| 4) it can be nested
|
| 5) it follows a more standard format (like most other patterns), unlike
| material_map, which is specialized
|
| 6) interpolation of the bitmap works better (see documentation on
| material_map for an explanation of why interpolation is not effective with
| material_maps)
|
|
| -Nathan
|

Post a reply to this message

On Wed, 26 Jan 2000 09:00:28 -0800 Ken <tyl### [at] pacbellnet> wrote:

>That was the very first question asked in this group when it was new.
>I know because I asked it :)

  It's a good question. Is this addressed in Warp's VFAQ (I've got to
get myself a local copy)?

-- 
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer

Post a reply to this message

Alan Kong wrote:
> 
> On Wed, 26 Jan 2000 09:00:28 -0800 Ken <tyl### [at] pacbellnet> wrote:
> 
> >That was the very first question asked in this group when it was new.
> >I know because I asked it :)
> 
>   It's a good question. Is this addressed in Warp's VFAQ (I've got to
> get myself a local copy)?

Actually the question has not come up that many times. If it repeats
again in the future there may be a need to include it in the VFAQ but
-I- don't think it's needed quite yet.

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

Post a reply to this message

Bob Hughes <omn### [at] hotmailcom?subject=PoV-News:> wrote...
> This gets edited into the patterns.htm file I have here immediately,
thanks
> Nathan.
> Didn't know about the "more than 256" thing.  Great, but I don't see how
it
> could.  After all, if there's only a 256 color palette or one 8-bit plane
of a
> 24bit image how does it apply textures to other than those specific areas
of a
> image then?  A kind of interpolation?

But let's just imagine that you're using a 36 bit PNG file as your input
file, instead of a 24 bit TGA.  (now, I have not yet looked to see if POV
will support a 36 bit image internally, but if not now, it probably will in
the future)

-Nathan

Post a reply to this message

Thanks All :)

I have played with image_pattern and well (I think :)) understand this!
Ok this is an interesting feature! For some use it is more interesting 
than material_map for many reason!
Great job :)!

Fabian.

Fabian Brau wrote:
> 
> Hello,
> 
> someone can tell me the difference between image_pattern and
> material_map? What can image_pattern do that material_map cannot?
> A simple example would be cool :)
> 
> Thanks
> 
> Fabian.

Post a reply to this message

In article <388faaaa@news.povray.org>, "Nathan Kopp" <Nat### [at] Koppcom> 
wrote:

> 1) it is not limited to textures; it can be used directly with normals 
> and pigments

And don't forget isosurfaces. Although you could use an image_map 
pigment, image_pattern would probably be more versatile(or at least far 
easier to get certain effects with).

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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