ZBrushCentral

Help with shattering a model.

ZBrush Usage Questions
#1

Fair warning I’m a relative newb to Zbrush but I’ve been in 3d for many years.
I need a statue I have made to shatter.

So I have a sculpted (whole) statue in Zbrush.

I also have the lo-res mesh (shattered) version, (like the bits of a dropped vase) in Maya. The cracks need to be specific so that’s why they are modelled, not procedurally generated. Some 250 pieces.

I am completely stuck as to how to transfer the detail from the zbrush sculpt to displacement maps into maya (rendering with renderman).

What I have tried so far is using the various projection tools to paint detail into the small pieces. But the pieces are deforming in ways that ruin the seams between pieces. They begin to overlap and develop impossibly thin edges.
The individual pieces have interior surfaces which don’t play nice when the exterior surface is made to fit.

Im stuck.
And screwed. :o

Any help would be appreciated. This cant be the first shattering sculpture right?

Streetsy

#2

it sounds to me like you need to use the actual geometry of the highpoly…or at least a decimated version.

shell that object and cut the model into pieces that you need.
use the LP pieces for the simulation calculations and link one to the other.

my 2 cents

#3

Maybe setup the lofi shattered object with poly groups for the inner pieces, so you can crease edges and hide geometry…subdivide and reproject.

#4

Thanks for the replies. Yeah seems the only way is the slooow way. Making each individual piece a tidy mesh, applying uv’s and then projecting to the outer skin seperately. Combining the inner and outer pieces in maya afterwards…

Id stay and chat but got lots and lots of stitching to do :slight_smile:

#5

Streetsy I think you are missing what I said…

#6

Sorry Jim I think I did. Looking at it now a bit closer. I have a quiet moment now to look at my options. Not sure how to crease edges yet. Looking it up now.

Cheers

#7

What I was saying is…

If you have a hipoly mesh, lets say its just a normal closed mesh.
And you have created by whatever means, a low poly object, cut it up so it has an outer skin which is cut up, and inner parts. In an external app set up so you have 2 poly groups, via selection sets or whatever. So when you reimport you low poly shattered object you now have 2 polygroups, Inner Pieces and Outer Pieces.

Append that as a subtool to the hipoly mesh.
Hide the Inner pieces.
Crease edges (it then goes back to showing all polygroups automatically)
Subdivide the mesh up to the desired level.
Take it back down to a lower subdiv level.
Rehide the inner pieces
Then project all with just the outer pieces visible.
Raise subdiv level
Project all with just the outer pieces visible.
Raise subdiv level
Project all with just the outer pieces visible.

Dont forget to set PA blur to a multiple of 8 (8,16,24,32 etc)

This might be geometry dependant btw… no guarantees here

#8

Sounds great. Ill give it a go.

(How does one select the edges in question?)

#9

Once you have your 2 poly groups (an important step), ctrl Shift click the poly group to hide the other poly group(s), ctrl shift click on the canvas to invert the selction etc. Set a neutral white material & put polyframe on, it will help.

#10

You have been a big help. Thanks Jim. The crucial thing I was missing was the creasing of the edges. (previous experiements had my surfaces overlap each other)

Also my base topo was a mess due to boolean cuts. I am cleaning that up now. With 271 pieces its going to take a while. But if it works then its worth it.

My only worry now is that the end displacement map doesnt have a massive difference between the outside and the inside areas,causing it to intersect at render time. I suppose a bit of blurring of the edges in photoshop might fix this.

Thanks again.

Streetsy

#11

Ok I have just tested it and it works.

#12

Theoretically if you have followed my steps, hidden the inner poly group whilst reprojecting, the inner surfaces displacement will be irrelevant. You just have to ensure you set the displacement distance in your target app correctly.

One thing to do is do some tests on a simplified setup so you are getting close to the settings you will need but with it all being easy to see whats going on.

Practically speaking I dont think you are going to have clean geometry (I did it with a fully triangulated messy mesh), and I dont think it will actually matter too much if you fine tune your projection settings so you dont get bizarre intersections… with a decent normal map and displacement map at a reasonable subd level it should all be fine.

Also I would make sure I was exporting a lower level subdiv of the high poly to cut up, to make sure its as close to the required geometry as possible.

HTH

Jim

#13

the inner surfaces displacement will be irrelevant.
If your verts are merged.

  • I would Crease BOTH the inner and outer pieces and ensure youre crease level is way up.
#14

Seems to be going ok. Got about half of the model done. Been testing the renders as I go. I few little verts going off into space but photoshop can erase those ok.

Thanks again for your help.

If the job allows Ill post up an image or two when we’re done.

Streetsy

#15

Cool mate. FYI forgot to mention a couple of extra things which helped my tests > using the groups loops function to add edgeloops before creasing, and also raising the target models subdiv level an extra step before projection.

#16

I did finish the model in the end. But forgot to post the finished spot. It can be viewed on the companies facebook page…

http://www.facebook.com/home.php?#!/video/video.php?v=418975226350&ref=mf