RE: [Visualpython-users] Planned work for Fall '01

[David S. <dsc...@vy...>]

> can we get decent looking results by choosing one standard 
> mapping? i mean, of course not, but if you just want to 
> import square textures you found as web page backgrounds to 
> spiff up your VPython programs, is "use spherical mapping for 
> everything" acceptable to people? (I say that because it's a 
> mapping that will look broken no matter what you do, so you 
> might as well not waste time trying to edit your textures at all).

Heh.  That's a really good way of describing spherical mapping :)

I think if you want a default projective texturing mode it should be
planar.  It's the only one that's reasonably easy to understand, and you
can do tiling.  But I warn you, any approach will be more complicated
than it seems.  How *exactly* does it rotate, translate, and scale with
the object?

> > I can also see some visualization applications for textures - maybe 
> > someone wants to draw contours on a height field, or heat 
> levels in a 
> > sliding friction simulation.
> 
> Right. So for that, tcoords and textures should just be 
> arrays accessible like the other atributes of faces.

Or planar texturing would be fine.

>   - Per-vertex textures for procedural texturing. Is this 
> applicable to
>     spheres or hexahedrons or whatever, or only to faces and possibly
>     convex? Of course this per-vertx texturing lets you 
> import models too.

Spheres, definitely not.  Hexahedrons yes, they are array primitives
with separate control for each vertex.  OTOH I was thinking that
hexahedron might be wrapped into faces with some interface tweaking.

>   - You probably also want a nice-looking mapping for each 
> primitive, with
>     a "template" texture provided to paint on, so if you want to do a
>     special goodlooking texture for one or a few primtives 
> you can, by hand.

I think anyone who can produce a "good looking" texture also can produce
3D models.  Is there really a demand for this?  I'm still waiting for
someone who will *use* this to speak up.

> How does POVRay specify textures for primitives? 

Chiefly procedurally.  In a raytracer color is most conveniently a
function of position, so they give you some basic 3D noise functions and
build up a material library from there.  Think Bryce without a UI.

I'm sure it also has bitmapped textures.  Just by knowing it's a
raytracer I would guess that it uses the projective approach.

> There's something else we haven't discussed: we presumably 
> want a Texture object, which can both import 2d data fed in 
> in code, and load some standard image files. There's an 
> rgbimg module for reading .rgb files, and an imageop module 
> that can do a few pathetic image operations. 

There's a library PIL that loads a lot of image file formats, and can
easily convert to/from Numeric.  This is a really dumb thing to write
ourselves.

Dave