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Heimhenge
03-09-2003, 09:33 AM
Looking through the objects library included with LW7.5 I've noticed (specifically with the Space/SolarSystem planets) that many of the surface maps have gaps or visible seams that look like huge tectonic rifts or splits in the planets' surfaces.

Is this a flaw with the objects? Or is there some default setting somewhere that I've failed to adjust properly?

Skonk
03-09-2003, 01:36 PM
Its caused by the way Spherical texture mapping works, ur taking a rectacular image and turning it into a ball, there will always be a point where the edges of the texture meet, u would usually get some scrunched up areas at the top and bottom and a long seam down the back. This isn't just in lightwave i must add, all programs have the same problem. One way to remove them is to use something like DeepPaint 3D that can actually paint onto the object its self, allowing u to spray over the seem. I think where are other ways to do it in lightwave but iv not used them yet :)

James..

Heimhenge
03-09-2003, 02:05 PM
I understand the geometric problem of mapping a rectangle onto a sphere. You'd think that if you got the equator and meridian to match up seamlessly (which involves nothing more than correctly scaling the width and length of the rectangle to match the circumference of the sphere) that everything would map properly.

The mapping engine in LW (or any other 3D app) ought to then merge the pixels near the poles as the meridians converge to a point.

I haven't gotten to that part of LW yet ... still learning, but I'm guessing there has to be a way in LW to do this correctly without having to buy another app.

So perhaps whoever created these objects just did a sloppy job?

NanoGator
03-09-2003, 04:53 PM
Is this in Layout or when you go to render?

OpenGL takes some shortcuts to texturing stuff that'll cause similar problems that you've described, so I thought I'd ask. :)

Heimhenge
03-09-2003, 07:15 PM
It's in Layout. I'll try rendering one and see what happens. Thanks.

Heimhenge
03-09-2003, 10:54 PM
NG: Aha! You were correct. When rendered the seam disappeared as you predicted.

Now the tough question ... what is it about OpenGL that would cause the seam to visible in Layout but not when rendered?

NanoGator
03-10-2003, 10:22 AM
Originally posted by Heimhenge
NG: Aha! You were correct. When rendered the seam disappeared as you predicted.

Now the tough question ... what is it about OpenGL that would cause the seam to visible in Layout but not when rendered?

Great!

It's probably because Layout's just trying to give you a little preview that updates as quickly as possible. As a result, they probably use a simple algorithm to spherically map the object with the texture, but as a result, the last row of polys gets the entire texture compressed into them.

There's a section in your manual that talks about 'discontinuus UV maps', or something like that. It shows how creating UV maps with an old version of Lightwave can cause a similar problem. It might provide a little insight into what's happening in OpenGL here.

For the record, Layout is just a glimpse to the final result. You might fire up Viper and get the hang of using it to preview textures, you'll have better (but not quite perfect) results then. :)

Heimhenge
03-11-2003, 10:23 PM
NG: Just got through the modeling chapter in the manual and am going back to UV section tomorrow. I have a couple of months of amazingly free time during which I intend to learn LW. I've used Viper a few times, but am still learning on that too. I think I understand what you're saying about OpenGL and Layout, and will continue to experiment.

This is such a blast learning what LW can do! I'm having just enough fun to outweigh the frustrating learning curve.

Many thanks for your suggestions.

NanoGator
03-11-2003, 11:57 PM
np. ;)

Trust me, it's very rewarding!