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MarkWood
07-27-2009, 10:19 AM
Hey there,

I am working with an Earth Model with a location on Earth that is to scale relative to the earth. Because of the massive size of the Earth model relative to the size of the vehicles in the scene the motion paths are becoming jagged and scraggly and some of the polygons are becoming distorted in the vehicle closeups.

This is due to the earth being full sized in the scene, but due to the global nature of the graphic everything has to be to scale. Does anyone know a fix for this?

Thanks for any help...

MW

dwburman
07-27-2009, 11:50 AM
LW does indeed have a problem when things are at such a great scale. I think the problem is due to objects being very far away from the world origin.

I haven't actually dealt with this problem myself but here are a couple of ideas you might try.

Perhaps just relocating (offsetting) everything so that the vehicles are closer to 0,0,0 would help.

Also, you might be able to parent everything to a master null and scale the master null so all the objects will be scaled together. That way you could be working on an earth the size of a basketball instead of actual size.

cagey5
07-27-2009, 12:01 PM
I've no real experience with competative products but this issue has been raised before and I believe all products will experience this problem to a certain extent due to the accuracy of floating point arithmetic at extreme value ranges.

toby
07-27-2009, 07:35 PM
This is quantization, and happens whenever you get too far from the origin. For example if lightwave keeps track of points in space down to .0001 degrees apart, and you go out into space far enough, those points will be miles apart from each other. Points on an object can only exist on the points in space that lw keeps track of, so the object distorts.

This is a basic problem with all 3d programs, but I think Maya has figured out a fix, centering the universe on each object or something.

But there's usually no need to have a full-size planet in your scene. Just use the chunk of planet that's in camera and move it and everything else to the origin.

ToMar
07-28-2009, 09:04 AM
But there's usually no need to have a full-size planet in your scene. Just use the chunk of planet that's in camera and move it and everything else to the origin.

Unless you zoom all the way out and around. I've build a 1:1 scale Earth (360 Rows, 180 segments) my self (8 segments b/c LW can't handel more the 8k Textures (or at least not the whole 16k X 30K Texture)) But i did not place anything on it...........yet

jameswillmott
07-28-2009, 09:24 AM
This is due to the earth being full sized in the scene, but due to the global nature of the graphic everything has to be to scale. Does anyone know a fix for this?



It's an issue with precision, if you want everything at such massive scales you can't really get around this issue.

But, if you showed us what you're trying to do it would make it easier to recommend a course of action...

toby
07-28-2009, 02:31 PM
Unless you zoom all the way out and around. I've build a 1:1 scale Earth (360 Rows, 180 segments) my self (8 segments b/c LW can't handel more the 8k Textures (or at least not the whole 16k X 30K Texture)) But i did not place anything on it...........yet
Heh, I was afraid you'd have something lke that - you can use a smaller earth, the difference isn't noticeable, and the important thing is to keep the action near the origin; so move the center of the earth to bring the surface near 0,0,0.

For the textures you could use Infinimap (http://www.db-w.com/index.php?option=content&task=view&id=55), it allows unlimited texture size.

MarkWood
08-07-2009, 04:00 PM
Yup. Originally I had the full scale sized earth, the placing a null at the origin, parented another null to that 0,0,0 null and then moved it all the way to the North pole, then by rotating the first null I could get any point on earth and have it be the 'parent' or master of the local scene.

But yeah, once you are 6 MM from the center of lightwave, and then adding in the rotation values from having that center null rotated...WELL, SPLAT...the geometry looses precision, and the motions, everthing except the earth was messed up.

So I isolated the area I needed, strip the rest of the globe out and just used the area, rotating it and placing it in modeller so that it would be 'ground' relative to a camera placed at 0,0,0 in layout.

Not too precise being that I had to eyeball the ground's rotation in modeller to make it look level right where the action is taking place, but close enough.

Yeah, once everything is back at the origin, no problems. Same motion paths look good, and polys are no longer distorted.

Maybe somebody should make a script that does the null thing (null at center of earth, null parented to it, then lifted up on Y axis until it is at North Pole, then the first null gets rotated to get the 2nd null where you want it on Earth, then using the 2nd nulls global position and rotation values, do the inverse to the earth, in a sense moving it down until the surface (NorthPole) is at the origin in layout and then rotating the earth in an equal (yet opposite direction) to make whatever location (Addis Abbaba or what ever) the place at the origin. Sorry if I am rambling...