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MAYA: - Boundary box over sized - Mirroring geo problem


Tia Biscuit
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I have a problem here I cannot for the life of me figure out. I get this problem all the time when working on detailed mesh. I've never found a fix for it.... sometimes ungrouping it and regrouping it to a new bit of mesh like freshly created cube fixes it... but usually I have to remake the geo. It is driving me crazy.

I'm trying to upload a bit of mesh and the boundary box in world on upload becomes to deep for it. Take this bit of mesh that is suppose to fit around the chest of the avatar. When I try to upload it.... it has a boundary box that reaches to the floor. There is no rigging or joints on it. I have carefully and throughly made sure there is no random geometry like a face or vert connected to it. The boundry box simply is associating it's size with the 0,0,0 position of XYZ in maya. There appears to be nothing in the scene doing it. This image shows what the preview window looks like when I try to upload the piece of mesh that is giving me this oversized boundry box. Its too high in the preview window, it should be in the center.

UploadPreview.png OversizedBoundryBox.jpg

The second image shows you the boundry box problem in world. 

Now I figured out what part of modelling is causing this..... Its mirroring and combining the two mirrored parts together.

When I mirror a bit of geometry. This boundry box occurs. If however I UNCOMBINE the two halfs of mirrored geometry and combine each half on its own and upload them. Each half's boundry box is perfect. However as soon as I combine them once again. The problem is back....

 

NOTE: this does not happen every time. It didn't happen to the top part that was also mirrored in the same way.


What I tried:
1. Exporting as Obj. Re-importing it.
2. Importing it to a new file.
3. Exporting it as a FBX. Re-importing it.
3. Duplicating and -1 scale along axis and freezing transforms and reverseing normals instead of using mirror geo option. 

So far nothing has worked. I've even recreated the chain, and the same problem pops up.

Somemone has mentioned that there is some residule math or something that lingering somewhere, and there used to be a purge option in older versions of maya. But I don't know where to find this. I'm using 2011. 

Any help very welcomed.
thanks 
Tia :-)

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Probably not going to be much help, but...

The uploader tries to work out the bounding box from the most extreme coordinates it finds as it loads in the triangles (or polys) from the coaalada file. However, at least for now, it does this by starting with the first position in the <geometry> section to set minimum and maximum for each dimension. Then as it reads in the triangles, it adjust them when it finds a position smaller than the minimum or larger than the maximum. That works ok as long as the first position in the <geometry> is referenced in a triangle. If it isn't, and it is outside the geometry, then the bounding box will be left including it, and consequently will extend beyond the geometry. I don't have Mayal so I can't check, but that is one possibility, that your operations are leaving an unreferenced vertex that gets included first in the collada file. You can look for this if you know how to peruse a collada file. Geometry can also be "lost" if you have too many triangles. I haven't tested this except with the Project Import development viewer, but it is possible that could have the same sort of effect. It takes a lot of triangles though. If you have only one material, it would have to be more than 174752. You certainly shouldn't have that many in a small thing like that.

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Yeah I had another guy tell me it was just corrupted geo somewhere. It is extremely frustrating. Because I even recreated it and the same error happened again and again with new geo. BUT a solution was found... for this file at least...

And that was to open it in 2014. (it was created in 2011) and apply new blinns to the model. Reset the settings of maya. It worked then. But I have no idea why. -.-

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I wonder if it is in your export settings?

When exporting a DAE file you only need "Polygon meshes, Joint and skin, Normals and Texture Coordinates" set to export in your options.  Could it be you have other things set to export as well like Cameras, Lights, Invisible Nodes, Geometric Tangents or a whole host of other things turned on in the options? (NOTE: You don't need Joint and Skin if you are exporting mesh that isn't rigged.)

This probably woudn't have helped but since you create jewelery there is a relatively simple way to create any size and shape bounding box you like.  This is great if you want to make super small or thin geometry smaller than 0.01 meters or if you want to offset the apparent pivot point.

1. After creating your mesh create a rectangular box and make it the size and shape you want it to be.
    (So if you want your mesh to be smaller than 0.01 in SL make the box much bigger than your mesh jewelery or if you want the pivot point to be offset make the box so your mesh inside the box is off to one side)

2. Create a mesh triangle and duplicate it 7 times so you end up with 8 triangles. (You can do this with fewer triangles but it is just 24 vertices.)

3. Make sure that in the "Move Tool" settings that "Retain component spacing" is turned off and that "Move:" is set to "World".  (Sometimes  "Retain component spacing" will act like it is on if "Move:" is set to anything else other than "World".)

4. In Vertex Mode select the all three vertex of one of the triangles and with "Snap to Point" turned on or hold down the V Key move your mouse cursor near one of the corners of the box you made for the bounding box and hold down your middle mouse button and drag it over the corner of the box. (All three vertex will snap to the corner of the box collapsing the face of the triangle making it invisible in Maya and will be invisible in SL no need for an alpha.)

5. Repeat the process for the other triangles snapping them to each of the other corners of the box.

6. Select just the box and delete it.

7. Select your mesh jewelry and all 8 triangles and combine then into one mesh.

8. You are now ready to export your mesh. (NOTE: You don't need to do this bounding box method for rigged mesh only for mesh that is not rigged)

What we are doing by adding the vertex of the triangles in this way is changing the overall size of your mesh.  SL doesn't care that the vertex is of the triangles are collapsed on top of each other making the faces of the triangles invisible in SL.  If you are doing different LODs just make sure that the 8 corners of each LOD are in the same positions as the original box and that your mesh jewelry or what ever you mesh is is inside the box completely.

Hope that helps. :)
Cathy

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"making the faces of the triangles invisible in SL"

Just to be annoyingly pedantic - :matte-motes-evil: - In fact the SL uploader does notice the collapsed triangle(s) used in this sort of technique, and it discards them from the uploaded mesh*, However, the technique works because it doesn't do that before using the positions of the verttices to update the bounding box. So you are left with the bounding box you want, but not the triangles. The best of both worlds.They are not just invisible, they are non-existent!

*You can see this is the case if you turn on Show Info->Render Info on the debug menu. Then you can see the selection triangle count near the bottom of the text that gets overlaid on the screen. It doesn't include the degenerate triangle(s).

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Ok I found something I might have missed on this first time around.

 

I just created another chain like this... and it was working perfectly. Then suddenly I had this huge boundry box.

What I found was that I couldn't freeze transformations. The error was that one of the polygons had incoming connections.

(I might have missed that last time around! I'm surprised I did as I had re-created the thing.... but anyway)

 

So I had to select the polygon in question... the error told me the name of the polygon. And either replace it or use the channel box to select the offending connections, right click and break connections. Then viola the boundry box problem vanished! Whooo yeaaah haaaa haaaaa! In your face boundry box!

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