loopsubdiv construction/syntax

[dougal2]

BTW, Radiance perhaps you might download Maya PLE and have a play with it when you have a spare moment. The file i/o stuff is restricted, but some of the code fragments I post might just run in it.

[Radiance]

hmmmm

Before: you take a simple mesh and apply subdiv in maya, export to lux as lots of polygons (trianglemesh shape)

Now: directly export the simple mesh and lux subdivs internally to lots of polygons (loopsubdiv shape

so the whole concept of creating this functionality around a maya subdiv object is wrong...
even if you can get the base simple mesh back, it's still not good enough as the user does'nt want to slow his maya opengl view to a grinding halt selecting a high subdivision level,
which is'nt exported anyways...

you'll have to do some clever thinking

can you not add a property to a normal mesh object or something ?

greetz,
radiance

PS: i'm near my bandwith limit (again), so no maya PLE at the moment...

[dougal2]

OK, forget about the "loopsubdiv" in Lux, lets pretend this thread is really about making sense of Maya's subdiv objects.

even if you can get the base simple mesh back, it's still not good enough as the user does'nt want to slow his maya opengl view to a grinding halt selecting a high subdivision level, which is'nt exported anyways...

That's the whole point of the subdiv geometry in Maya, and this is why it's different from regular polygons.
The subdivision is not applied to the whole mesh, but only locally in the areas you've edited. This is what I mean by subdiv Levels in Maya. The different levels are visible simultaneously and can be edited independantly. Those little screenshots I've posted in the first post show 2 subdiv Levels on the object - it's not a composite image.

When exporting this geometry, what I can do is export only the faces that exist in a particular level - there is never any need to either export or view the whole object at the finest subdiv level.

I'm going to do some work now to validate what I'm exporting from different levels, hopefully I can shed some light on the problems I faced last night.

[Radiance]

hmmm

I see, but i don't think thats possible at the moment.

The loopdiv shape does'nt support different levels for different groups of vertices.
Exporting the different levels as different loopdiv shapes won't work either, as you'll end up having tears/holes in it (because vertices between groups won't be connected)

I think it might be best to stick with attributes on normal mesh objects or similar in this case...

greetz,
radiance

[dougal2]

The loopdiv shape does'nt support different levels for different groups of vertices.

That's not something I'm trying to achieve. The levels I'm referring to are != "nlevels". They are simply a subset of the faces in the mesh.

Really, I simply need to knwo wht the following valid object doesn't work as a loopsubdiv:

Code: Select all

# Polygon Shape |pSphere1|pSphereShape1 (set 0)
AttributeBegin
   ConcatTransform [6.000000 0.000000 0.000000 0.000000
                    0.000000 0.000000 6.000000 0.000000
                    0.000000 -6.000000 0.000000 0.000000
                    0 0 0.000000 1.000000]
NamedMaterial "lambert1"
Shape "trianglemesh"
   "integer indices" [

0 1 2
0 2 3
1 4 5
1 5 2
2 5 6
2 6 7
3 2 7
3 7 8
9 10 11
9 11 12
12 11 5
12 5 4
15 16 17
15 17 18
16 19 20
16 20 17
21 22 23
21 23 24
22 8 7
22 7 23
23 7 6
23 6 20
24 23 20
24 20 19


   ]
   "point P" [

-1.375000 -0.000000 1.375000
-0.750000 -0.000000 1.750000
-0.875000 -0.000000 0.875000
-1.750000 -0.000000 0.750000
0.000000 -0.000000 1.875000
0.000000 -0.000000 0.937500
0.000000 0.000000 0.000000
-0.937500 0.000000 0.000000
-1.875000 0.000000 0.000000
1.375000 -0.000000 1.375000
1.750000 -0.000000 0.750000
0.875000 -0.000000 0.875000
0.750000 -0.000000 1.750000
1.875000 0.000000 0.000000
0.937500 0.000000 0.000000
1.375000 0.000000 -1.375000
0.750000 0.000000 -1.750000
0.875000 0.000000 -0.875000
1.750000 0.000000 -0.750000
0.000000 0.000000 -1.875000
0.000000 0.000000 -0.937500
-1.375000 0.000000 -1.375000
-1.750000 0.000000 -0.750000
-0.875000 0.000000 -0.875000
-0.750000 0.000000 -1.75000

]
AttributeEnd


Here's a render of it as a trianglemesh:

Here's the vertex and tri numbering:

[CTZn]

Here's my contribution; hopefully that will help finding a good basis for communication:

A Short Introduction to Maya's SubD's

Radiance, am I correct when I assume that the last object shown is what lux expects as input for loopsubdiv ?

Ah crap there are permissions issues, hold on... K I'm attaching the file if possible... well nope.

I'm on this, will post again.

[dougal2]

CTZn
Thanks for the vid.

Also, there are indeed 2 issues in this thread.

#1 Outputting verts and indices in an optimised fashion.
I'm reasonably confident that I'm doing this correctly. I've adapted my code to work on normal polygon meshes and I'm getting nice shared vert output that converts nicely to Lux's loopsubdivs.

#2 Reading vert info from a Maya subdiv object
This works when working with a single subdiv level in Maya, and saving the output as a Lux trianglemesh.
Specifying a single level as a loopsubdiv doesn't work.
Trying to output all visible levels into one Lux mesh doesn't work, either as trianglemesh or loopsubdiv.

I hope that clarifies.

I have at least worked out the optimised mesh stuff that is handy for some mesh situations, even though I still have questions that need answering about it.

[CTZn]

Ah you could see it, I couldn't

The only part that's different for me is the "adaptive convert subdiv to polygon" that tesselates the entire object to the highest level ??!

No, that is what the "uniform" method would do; adaptative tesselates the object according to the highest local level edited. Backfaces in the demo object are coarse. I think it's fine as is.

Attached the final mesh:

[dougal2]

No, you're right, the convert worked properly this time.

Here's a render of:
1. create subdiv cube
2. edit the same (ish) as you did in the vid
3. adaptive convert to poly
4. export via my optimised mesh output routine, including triangulation
5. render as trianglemesh and no normals so that you can see the triangulation.

[CTZn]

Fine, I did my job