I don't get it !

1.) image_pattern ?

  There is a new pattern type included with the Photon Patch of Pov-Ray
called "image_pattern". What is the purpose of this addition. I looked
at the example given at Nathan's patch site and read the description
but I am not following the reason for it's existence and when it is
appropriate to use it. I had no problem recreating the example image
shown at the site with existing texture and pigment procedures.

2.) U_V Mapping

Concerning the u_v mapping function in the patch. I tried using it with
a mesh based model and had less than successful results. Could someone
explain a little more on the process involved in it's implementation
and usage. I understand well how it works with bicubic patches as that
is well documented and I have read the posts here on the topic. As applied
to a large mesh object on the other hand all I am getting is a solid
colored pigment effect rather than the image hugging the mesh object
as expected. Anyone ?

  And thank you for your continued support !


-- 
Ken Tyler

mailto://tylereng@pacbell.net

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ken said

> 2.) U_V Mapping
>
> Concerning the u_v mapping function in the patch. I tried using it with
> a mesh based model and had less than successful results. Could someone
> explain a little more on the process involved in it's implementation
> and usage. I understand well how it works with bicubic patches as that
> is well documented and I have read the posts here on the topic. As applied
> to a large mesh object on the other hand all I am getting is a solid
> colored pigment effect rather than the image hugging the mesh object
> as expected. Anyone ?
>

 The "supported" primatives for uv mapping have inherent uv spaces. The thing

with triangles is that you have to describe this space yourself. You could do

this by macro'ing an object from triangles that describes the uv space as it
creates the object or use another piece of software to do it. A straight mesh

that just contains triangle info doesn't have any inherent uv space. To get
uv mapping to work, each triangle in your mesh must have a uv space defined
for it as per the bottom of Nathan's uv mapping pov page.
(http://nathan.kopp.com/uv.htm)
Other highend modellers facilitate uv manipulation when texturing meshes
(like texturing in 3d studio or something and then saving to .3ds format)
then would then have to use a converter that would convert triangle info
aswel as triangle uv coords. ...(doesn't the latest ver of 3ds2pov do this??)

benp

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Ben Paschke wrote:
> 
> Other highend modellers facilitate uv manipulation when texturing meshes
> (like texturing in 3d studio or something and then saving to .3ds format)
> then would then have to use a converter that would convert triangle info
> aswel as triangle uv coords. ...(doesn't the latest ver of 3ds2pov do this??)
> 

3ds2pov does convert 3ds files with textures and uv coordinates intact.

-Nathan

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Ken wrote:
> 
> I don't get it !
> 
> 1.) image_pattern ?
> 
>   There is a new pattern type included with the Photon Patch of Pov-Ray
> called "image_pattern". What is the purpose of this addition. I looked
> at the example given at Nathan's patch site and read the description
> but I am not following the reason for it's existence and when it is
> appropriate to use it. I had no problem recreating the example image
> shown at the site with existing texture and pigment procedures.

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).

-Nathan

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Nathan,

  If you get a chance stop by the images group and look at the
 post titled Patent Pending. The reason is explained there and
 is related to the "other" features of the patch.

 Thank you,

 -- 
 Ken Tyler

 mailto://tylereng@pacbell.net

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