How to make polycube from vertices

[amitc]

Hello,
I am try to make polycube(s) from vertices.

I figured out it could be done by
1)creating triangles (polyCreateFacet blah blah blah)
2)polycube command that lets you create a cube when you give l,b,h etc.

Is there a method I can create a cube just by giving 8 points ?
Although I am calling it cube but it is a distorted box so there is no length, width and height relationship.

I have to create 100,000 of these
1) so creation by triangulation is not a good idea because lots of double edges will be formed.

2)Copying a unit poly cube and moving vertex will cause a ton of overhead and maya would die doing this for large number.

Eventually all these vertices will move at different timestamp in a varying manner.
Think of this as exploding wall where each polycube is a stone of some shape(with 8 vertices) and then it distorts(explodes but vertex count remains same)

It would be very helpful if you folks can suggest some methods/ideas to handle this

thanks!

[joojaa]

the poly create face can create quadfaces too just ad a 4 point to the equation. So basicaly if you know the order in wich the points come in you could device a mel procedure to act on it.

Id just make a poly cobe and move each corner repectively form there (thisway you get a uvmap easier).

[naughty]

you don't need to worry about double edges if your triangles (or quads as joojaa suggests) are using the same vertex positions because once you've created them you can just weld all the vertices/edges together.

the only way to throw 8 arbitrary points at a procedure and hope to arrive at a solid object is by using a convex hull algorithmn. there is one on highend3d in the MEL scripts folder called "create_convex_hull.mel". I haven't tried it though but I believe it works. (although you'll have to edit the code a bit to input 8 points, rather than it's defualt behaviour of taking selected components...)

:nathaN

[failure]

"Copying a unit poly cube and moving vertex will cause a ton of overhead and maya would die doing this for large number. "

I think you should do exactly this. I don't see any overhead involved here.

Using convex hull algo to build cube-like objects is just silly

[naughty]

yeah I agree, I presume from Amitc's original post that he does know which of his 8 points corresponds to each cube corner, and he only wants slightly deformed cuboids, in which case there's no problem modifying a regular cube but what I was saying is that if you just have 8 arbitrary 3D points (that could be anywhere), you can't just align a different arbitrary point of a cube with each one cos you'll probably end up with an intersecting mess...

:nathaN

[amitc]

Thank you guys for your comments.

By past experience I have seen there is an enormous overhead when you make object and transform it. Doing this at vertex level is going to be worse.

createfacet probably would be most effiecient (triangles/quad) but I still have serious concerns when I try to move these 100,000 vertex driven by script.

Anyways I'll post back once I have come up with something or failed. If someone gets a brainwave please do post it.

Thanks!

PS: I did the something similar to createfacet method 2 years back on 3dmax (did not know maya then) guess what my machine died everytime ( I did whatever I could to optimise ). I am hoping maya would overcome this problem and complete what I set out to do way back

[failure]

"there is an enormous overhead when you make object and transform it."

This is as basic as it can get. Everything else will surely involve more overhead.
Be sure to delete the creation history of your objects

"but I still have serious concerns when I try to move these 100,000 vertex driven by script"

You can use particles with instanced geometry.

Or do it in several passes and composite it.

Anyway maybe it's a good idea to post what exactly do you want to achieve. Maybe someone could suggest you a better method.

[amitc]

Its the data for collaspe of a structure.
So I have bricks with all vertices and conectivity information and then I have the vertex displacements for subsequent timestep.

So in essence its vertex position and there movement in time. Particles might not be suited as there is deformation for individual particle which would be tough to control in particle paradigm.

[failure]

I see. So you have simulation data from some other source.

I would do like this:

First, I'd make a script that loads in a complete animation data but for limited number of randomly chosen vertices ( say 5% or less of your total set ). Then make anim curves out of it and feed the curves to locators. Now you have rough preview of general motion. And it should play ok in the realtime.
Use this preview to animate the rest of the scene ( camera motion, lights etc. )
Next, I'd create several poly cubes, properly textured and each with slight variation in tone/texture. These will be source geometry for final objects.

For final render I would use pre render mel feature. That way you'll never have to deal with half a milion cubes in your viewport ( everything happens just before/after frame is sent to renderer )

Before rendering:
-load the vertex data for the first frame
-repeat for each 8 vertices:
----randomly choose one of the prepared cubes and duplicate it.
----move it's verts according to input data

Pre render mel script:
-load the vertex data for the current frame
-repeat for each cube:
----move it's verts according to input data

[joojaa]

Also when importing data you will get a bit of extra overhead because you have history and UNDO on. Just turen them off before you start doing this.

Also i suggest you do this all in batch without ever obening a maya ui at all... Saves you helloffalot of time (or just dump it straiight to individual maya files and render each one sperately a bit like you would with a rib stream)

[amitc]

folks,
Unsuccessful on first attempt.
I tried to make a polycube duplicate it and move vertices to the position driven by input for just one time step. (75,000 + cubes with about 92,000 vertices)
undo and construction history were turned off.
No result in 24 hrs + amd 1.4 ghz, 512 ddr ram
I'll post the script in evening when I get home for you guys to have a look.

Joojaa please let me know how to lauch mel script from command prompt.

Next thing I have in mind is to try and make say 10,000 cubes at a time and then merge the scene.

Also as failure suggested it'll be neat to create some cubes and randomly pick them which should create good results. (if script works)

Thanks
--Amit

[gmask]

If you launch Maya from the commandline you can launch it without the interface

maya -prompt

or

maya -prompt -file someMayaFile.mb

then run your mel script by typing in it's name then afterwards type file -save

[amitc]

Folks,
I had a grave error in my script an infinite loop.
After fixing it the code flies everything done in 500 sec
BUT its takes an hour to save the file which is 82 mb.

And maya freezes after that you cannot see what is there or looks like in the viewport.

Even when I kill maya and open this file in a new session maya freezes after reading the file.

I have 75000 poly cubes with 92,000 vertices

Please have a look at my script here and let me know what optimization can be done.
view script

I am fearing what would happen when I have all these vertices move around with time. Something is wrong there should be a way to accomplish this.
Thanks
--Amit

PS: Thanks qmask for the tip the maya prompt makes work done faster

[gmask]

Would it be possible to create a particle system and use particle instances to copy the cubes to the points?

[amitc]

Qmask partciles mostly are not good idea in this case

Even though they are polycubes I am actually distorting them by moving the vertices, so every cube is of a diffirent shape and will change with time. This means instancing is not good enough I have to eventually get down to every instance and change the shape which is what I am doing with polycubes

With my limited particle experiecne in maya this might not be posiible to achieve with moderate effort.

I can also spend some time on using triangles or quads for making this thing but performance would be worse than this perhaps.

what do you folks think?

--Amit

[joojaa]

No but youd make a softbody wich instead uses the particlarticles to drive the points.

Quadrangles have less info (about one edge)

Anyway... Is it imperative that you get feedback of the anim in the viewports? I mean i would make some rough proxies for the camera movements. Then dump out a maya ascii file with all the data and just put the elements together just in time for render. Thats how 90% of our pipe works anyway.

What kind of system are we talking about for running this data on?

[failure]

You can always get away with making several passes and z-compositing it all together.

[amitc]

"No but youd make a softbody wich instead uses the particlarticles to drive the points. "

Joojaa could you throw more light on this and method to accomplish this.

Thanks

[failure]

"No but youd make a softbody wich instead uses the particlarticles to drive the points. "

That will produce so much unneeded overhead. ( for example, just check the reference and compare how much more attributes are stored per particle than per poly vert )

Don't complicate. Divide and conquer. Use compositing.

[amitc]

Yeah! ultimately I have to get down to compositing.
this is just one part. I have 4 elements with 100,000 + vertices.
Today I am gonna try to move the polycubes I created earlier lets see what we get.