just a little curiousity from me today,

was wondering if anyone knows of a program or util that can make an object (.obj, 3ds,etc)from a uv map alone.

it just sounds plausible to me that if you can have a program that can make a uv map from an object, that there could also be a program that could make an object from a uv map,

so does anyone know if there is one please?

Interesting idea.  The basic problem is that the UV map doesn't tell you how
the object is "wrapped".  The map is a flattened-out picture of the mesh,
but the flattening or projecting process could have happened in an
infinite number of ways.  

One thing you could do: use a bitmap-to-DXF converter to turn the map
into a flat mesh, then take the DXF into a modeler and use your intuition
or knowledge to wrap it back into the right kind of 3D shape.

Yah. The problem lies right in the "U" and "V." A mesh contains vertices at cartesian coordinates X, Y, and Z. Additionally, the file format contains information on which vertices are connected by lines, and which resulting polygons are filled (the .obj format can also contain information on surface normals, but Poser ignores this, preferring to make up its own). Parallel yet independent to these cartesian coordinates in three dimensions, each vertex may also have coordinates in an additional 2 dimensions; the coordinates of U and V. (Or is it a coordinate of the center of each polygon? I forget!) Technically, every polygon on a UVmap could be detached from the others and moved to some random part of the map. Nothing requires it adhere in any way to the original shape of the mesh.

This picture illustrates the basic problem, even in a nice 
predictable mapping.

These two hump-thingies have exactly the same UV map, nothing
fancy.  Both are mapped in the same way (planar on Y, no split) 
but the map doesn't tell you anything about what's happening on the Y axis.

jeez, just think of the nightmares modellers would experience if their models could be extracted from free templates. I've never heard of it done, however. p.s. it's the co-ordinates of the vertices.

thanks!!! 

i was wondering about it from a mixing figures together point of view, a kinda posensteins monster if you like, whether if it were possible it might elimate the problems faced when parts have a different number of vertices where you are trying to join them.

ockham, are those pink and blue results exactly the same settings on everything but that is showing the randomness of the results?

miss nancy, as soon as i had written it i wondered how long till someone would mention the downside if it were possible (LOL)

Don't be completely discouraged by the downside.  There could be
a useful idea somewhere in the vicinity, even if the original
thought doesn't quite do it.

I doubt that it would help much on welding two pieces together.
Usually that means building a "bridge" between them.  In some
cases the modeling app can make such a bridge automatically;
in other cases it requires hand-drawn facets or adjusting or dividing
one of the pieces.   But those processes have to be done directly 
on the vertices themselves, so the UV map wouldn't
add useful information.

= = = = =

The pink and blue thingies have the same grid pattern, and when
seen from above (in a flat non-perspective view) they look just the
same.  So when UVmapper does a planar map on the Y-axis,
it creates exactly the same picture.   The thingies could even have
lots of bumps and dips, and they'd still have the same map
as long as the mesh was morphed vertically.  

Which is also a great illustration on the essential problem of UVmaps -- it is impossible on most objects to obtain minimal seams, equal-sized polys, and parallel lines (as they exist on the original shape), all at the same time. You always end up optimizing one over the other. A cylinder can be mapped so that there is only one seam to blend, and a square drawn on the texture will result in a square appearing on the surface -- a stripe across the texture will be a stripe around the cylinder, a stripe up and down will be a stripe down the length of the cylinder. But change to something as simple as a tapered cylinder (or a barrel). Now, no matter what you do, you can not make a map where a ring at the top and bottom of the tapered cylinder are both straight lines on the texture and of equal relative proportion. It is no longer possible to flood-fill texture (not in itself necessarily a bad thing...!)

ok i'm probally about to step out of my fathoming of things range here but, 

would a displacement map, attached to your thingies alter how they present themselves in a controlable manner?

do you know of anything (hopefully free) that can do that bitmap to DXF conversion bit please?

I'm not following. Could you elaborate?

sorry nomuse, they were aimed at ockham, as he mentioned creating a flat mesh in a.DXF format from a .bmp image so i wondered if you then attached a displacement map to that mesh whether you could alter its appearance ie. turn it into a sphere.

am wondering now though if you have a barrel made with a cylinder and texture it from that cylinders uv map whether if you add a displacement map whether you could get it to bulge in the middle, but keep your ring lines straight?

Yes to the latter. It's one or the other. If you keep the barrel's rings straight, then your staves are distorted towards the middle; you have to do extra work in your painting application to make the gaps narrower in the center of the map, wider at the ends....and the same squash/stretch of the wood texture.

vince, I think they use illustrator paths for that. but the model info can't be extracted from the displacement map either, AFAIK.

i'm thinking of a displacement map to rebuild/shape the mesh, not to extract model info from.

(trying not to expose the downside or consequential vunerability at the same time, if that's possible)

Quote - I'm thinking of a displacement map to rebuild/shape the mesh, not to extract model info from.

Wont work, cause disp maps use the mesh info itself to do their mojo... Usually a disp map 'bumps' the mesh only along its normal. If the mesh is flat, like it would be in a UVmap-mesh, then all you would get is a mountain like result, not a sphere or a barrel.

A normals map, tho....

A normal map can work but it will only be an illusion. So the UV-mesh will look like a human if you look at it head on, but as soon as you rotate it, you will see the flatness. It wont actually affect the mesh geometry.

There is an advanced form of diplacement which can do this, but very few apps support it. It's called vector displacement, and AFAIK only mentalray has it.