Pretty Poly Editor Documentation
III. Discussion Topics - 2. Texture positioning
I want some discussion about texture positioning going. I (Wolfram Kuss) have never
seen a modeller (including my own) that has easy-to-understand input of arbitrary
texture coordinates (TCs).
In this chapter I am NOT speaking about cylindric, spherical and box-texture-mapping.
They don't allow for arbitrary texture coordinates.
One of the nice things about having orthogonal view is you pretty much get a uv
coordinate manipulator for free. View classes should be capable of displaying textures
in the background as a trace aid for modelling. Thus UVEditor is essentially a
sub classed XY view that simply renders all the objects using the UV coords as geometric
XY coords. Add a move method to move UV instead of XY, and display an object's texture
as the background, and you have a pretty functional uv map editor. This is also were
having multiple view windows is a plus, as you can edit UV in one window, and view the
3D results in another.
So some questions to the readers:
Do you think arbitrary TCs are important?
How important is using scanned textures, painting texture in 2D, and painting texture
in 3D?
Have you seen a modeller with good texture positioning or do you have dreams how it
should work?
How could an interaction between UV-view and 3D-view work?
I think it is often important to work accurately. How can this be achieved?
Another problem is that texturing might mean that at one point in space there are several
vertices. Look at this picture
Lets say you want to texture a cube. It doesn't matter whether you want one
texture on all sides (for example a marble), or different textures or different
parts of one texture on the polygons. But lets say each polygon gets its own
texture. You start assigning texture coordinates on polygon A. They are 2d-coordinates that
range from 0 to 1. Lets say you only have one vertex per point in space and one TC
(=one 2D vector) per vertex. Then two of the TCs for polygon B are fixed, since these vertices
are shared with poly A. You HAVE to assign a TC of (1,0) to the top right vertex or the texture
on Poly B will come out distorted. On the top polygon (C) you now have twice the TC-value
(1,0)! This will lead to major distortion, since one texel will be mapped onto the hole
line between the two vertices. This is not acceptable, so there are only two solutions:
Have more than one TC per vertex (thats what I did in my modeller) or have
several vertices per point in space. PPE uses the later approach and it seems to be very hard
to change to the first.
So, one question is, how easy is it for the PPE-user to live with this and how can we (developers of
PPE) help him or her?