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Old 22nd March 2008, 01:21 PM   #1
Doomz
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Default Linking=merging?

Ok this seems like an odd question but how to you 'link' or 'group' objects together so they export into one object using the Second Life sculptie exporter? Not sure if im explanining this well enough. Any info appreciated. Thanks
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Old 22nd March 2008, 06:24 PM   #2
lisa
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Default Re: Linking=merging?

Hmmm... not sure quite what you're looking for? If you name each object differently (in the object properties), the exporter will export each object as its own sculpt map. Those can be linked as prims when you export them into SL.
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Old 22nd March 2008, 06:38 PM   #3
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Default Re: Linking=merging?

so theres no way to 'combine' the objects in AC3D in order to export it as one prim into sl?
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Old 22nd March 2008, 10:58 PM   #4
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Default Re: Linking=merging?

Ah, ok... you can depending on the object... *but* you also have to merge the UV map correctly. The uv map has to cover both shapes as one continuous sheet. If you are merging two things into one shape, it may be possible, if it really is two distinct (cut-apart) objects, it can't be done.**

Remember, in SL a sculpted prim is really just a deformed sphere. If the shape you want can be made by reforming a sphere (without cutting it into more than one shape) than you can make it from one sculpt map. Otherwise, you need more than one sculpt map.

[** Caveat: I hate the word "can't"... the truth is, you probably can make a single sculpt map into more than one shape by using degenerate triangles. A lot of game engines use this trick with triangle strips. However, unless you are an expert modeler and texture artist, I would not recommend attempting this.]
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Old 27th March 2008, 01:25 AM   #5
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Default Re: Linking=merging?

A quick question: I don't know in what file format that SL uses nor how different it is from the VRML 2.0 format ( I'd bet alot) but; in my first; some of the items in the Glyph were made as separate objects and the -Object -merge option worked for me to make it all one object. Of course it had to be in the Group mode. I'd appreciate any clarification to the differences in the two formats.
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Old 30th March 2008, 06:04 AM   #6
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Default Re: Linking=merging?

Yes, they are *very* different.

VRML is primarily a polygon-based file format. It stores triangle, vertices and normals in its model file. Many 3D formats are very similar to this.

Second Life on the other hand uses parametric shapes, specifically conic primitives. i.e. sphere, cone, cube, torus, and all the twists and variations that are possible by altering the input values to the parametic equation. Each shape is called a "prim" in Second Life lingo.

Instead of storing the actual vertices or triangles, it stores the values of the different shape equations. So, something like a sphere might be saved just by saving its center point, radius, twist, and hollow. Second Life is one of relatively few 3D programs that works this way. One of the other programs that works this way is POV-Ray, although POV-Ray will also handle polygon data in addition to parametrics.

In *theory* Second Life's way of storing models is much, much more efficient than a polygon model. In *practice* it's a little more hit-or-miss. Because the limits in prims make it hard to make certain kinds of shapes, people end up using *lots* of prims to try and get the shape they want. It's not unusual to see hair or jewelry with 50 to 200 prims in it. Unfortunately, because of the way video cards work, prims still end up getting converted into triangles when they are rendered. Some shapes end up with lots of triangles (up to 1024 in a torus). So, having a 100,000 polygon hair style isn't a stretch. Obviously, if you have a crowd of people dressed this way, it's going to start running pretty darn slow in no time at all.

That's where "sculpted prims" come in. A sculpted prim is Second Life's way of getting polygon-like data into their pipeline, which is designed only for parametric shapes, in order to help cut down on the number of wasted polygons. A sculpted prim is really just a sphere with a displacement map. If you've ever used a heightfield in POV-Ray or made terrain with a landscape editor, it's the same thing only wrapped around a ball. The displacement maps used by sculpted prims also let you displace a point in x,y,z instead of just y the way most landscape editors do.

There are three AC3D exporters. The "box" and "tri" exporters both create lists which then are used to create standard "prims" (parameterics) in Second Life. The third exporter creates "sculpted" prims, which it does by reading each point on the model and then writing the displacements to a texture map, which Second Life will import and apply to a sphere.
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Old 5th April 2008, 11:45 AM   #7
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Default Re: Linking=merging?

Lisa; Thank you for your explanation, it is very informative and has taught me alot. But.. that leaves me the same question:
While in AC3D, the model is in ac3d format, and at that time, why wouldn't (while in Group Mode) -Object -Merge, combine the objects into a single object; before the export into any other format?
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Old 5th April 2008, 07:26 PM   #8
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Default Re: Linking=merging?

For box and tri creators, what you suggest would work.

For the sculpted prim format, however, the problem isn't the objects... it's the uv map. The texture also needs merged (without any holes or overlapping faces) and there is no automated way to do this.
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Old 5th April 2008, 07:30 PM   #9
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Default Re: Linking=merging?

Ah I see. thank you again, your the bomb Lisa!!!
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