Retopo this...?

AnimeAngel

Hey guys,
So I have this mechanical model that I modeled in Max.





I now want to take this model and use zbrush to sculpt on the finer details like screws and bolts. This object and all other objects with it have to be watertight and I can't use any floating geometry, Thus why I have to sculpt in the bolts and screws rather then floating them. The problem is that if I take it into zbrush and then divide it to its max, the geo is really dense in areas, like the edges, but even at max division many of the flat areas dont have enough geos to sculpt on.
So I am thinking that I need to retopo the object to get a more even distribution of geometry but I can only find refrences of people retopoing character models and not mechanical models.

Am I correct in assuming that I need to retopo this to get the result I want? And if so how do you go about doing that to a mechanical model, so that I ensure I don't lose my edges but get a even distrubution so that I can sculpt on it?
It should also be noted that I have Max9 and zbrush2 or zbrush3 trial.
Any help would be apriciated. thx.

Neox

why exactly do you need it as a watertight mesh? but anyways for an object like this i'd rather model the stuff instead of sculpting it

Mark Dygert

1) Who told you you can't have floating geometry/sub tools in Zbrush? Find them and punch them in the nuts.

Use floating geometry. Not only will it allow you to create a base mesh quickly but it will allow you to sculpt each piece without having to worry about the overall density. Meshes don't need to be water tight, they just need to be easily sub-divided. Welding it all together is insanity, in my book, unless you have a really good reason...

I would suggest checking out the first part of the Eat3D pillar video. He walks you through the steps of creating a model in max that will sub-d well and makes a good base for sculpting.

2) If you want more density in the large areas you should pre-sub divide them.

3) I see a lot of tris? Classically that's a recipe for disaster when sub-dividing models. Floating geo would have probably gotten you around a lot of those tris...

4) Whats the point of sculpting? Most of the detail in mechanical things can be done a lot easier through standard modeling.

AnimeAngel

It has to be watertight because its intended to be printed. Thus why no floaters allowed.

There are little to no tris in the mesh. I was very careful to ensure that the majority of polys are quads. I think there is only like 8 tris on the entire mesh

I was thinking it might be easier to sculpt in all the little screws and bolts instead of cutting and extruding each one of them in max because as Vig say, welding and stitching all this together is pure insanity. But if you say it will be easier in Max, then I better get to work because that's a lot of tiny pieces to add in.

Are you talking about this tut VIg?
http://eat3d.com/free_meshlab_polygon_cruncher

Justin Meisse

Shapeways sez overlapping meshes are fine but there's an issue where their software calculates the total volume of each mesh as far as pricing but I don't see a bunch of little screws really bumping the total volume up that much.
link

EarthQuake

One of the biggest problems you'll have with doing it in zbrush is that your mesh is doesn't have evenly distributed quads, and by that i mean mostly even sized polys in a simple grid pattern. Whats going to happen is as you sub-divide it, you'll get tons of really long quads here, tons of triangle shaped quads there, and tons of huge quads in other spots, so you'de have to sub-divide the thing to like 20 million tris to be able to correctly do the detail you want. Which is likely too high to submit to a printing company unless you optimize it.

To make the process in max easier, i would suggest blocking out all of your screws etc as floating geometry, placing it in the correct spot, with the correct geometry, and then its just a matter of deleting some of the surounding geometry around that screw, and reconnecting it to the geometry of the screw.

Also another misconception you may be operating under, "watertight" generally means that you cant have any open edges, it doesnt mean that everything needs to be 1 mesh. You can have intersecting meshes etc. So if you want to slap bolts on that aren't supposed to be indented into the mesh, just slap them on, make sure the end is capped, and make sure they are intersecting the main mesh a bit and you should be good to go.

AnimeAngel

Ah thanks EQ! That sheds a lot of light on a very dark area.
When I tried to divide it in zbrush I did get exactly as you said and I don't have the computer to push a 20 mill polygon model, so going to that level is defiantly out of the question.

This model is part of a much larger model which I have been posting WIP of in the preview section. It is for the creature and critter competition on CG coach. The winner gets their model printed in 3d, so the model has to be made with that in mind.
They told us that all objects had to be closed but didnt mention anything about intersecting geometry. I assumed that since they said closed, that that also meant all objects needed to be attached and not intersecting.
But if it is as you say it is then making some screws and intersecting them with the mesh would be a ton easier then welding them all in or sculpting them in.

Mark Dygert

Ahh 3D printing... gotcha.

I'm not sure how the hoses will print, they may need to be done separately and attached? Might want to check on that, it depends on the machines they use but I think in general terms that is going to cause problems.

Also it depends on the place you have it printed at, but there are places that take floating geometry.

Seaseme

The hoses should print fine.. Depending on what kind of printer they're using I suppose. The ones I've seen and have experience with could handle the hoses with no problem.

Neox

never had problems with sticked in stuff for printing but didn't print that much, but from what i know floates don't work thats right but two closed meshes intersecting are nor problem

but you could also take 3dcoat or another voxelbased tool, convert your geo into voxels (there you could also set up the density and size and see which of your details really hold up the resolution) and export it to stl or some format the printing company supports

Mark Dygert

http://www.cadspan.com/info
CADspan takes any kind of mesh you toss at them. SketchUp, CAD, 3dsmax. As long as it looks like it can be printed they'll take it, this includes intersecting geometry. It may not even need to be capped off?

They use some custom software which basically takes a closed highly dense mesh and shrink wraps it to your model, then they print that. It's really accurate and something everyone should be doing soon. Having people model closed continuous meshes is insane and needs to die as quickly as possible.

I was talking about the Pillar DVD tutorial. He covers sub-dividing to roughly even quad patches like EQ was talking about.

AnimeAngel

Well I believe the hose should be ok. They just specified in the contest guidelines that as long as it has a good thickness then it will print fine, So nothing like thin strands of hair or anything but I made the hoses as thick as they are just to make sure they would be printable.

The company that is putting on the contest is http://www.moddler.com/ and I wish they had the same shrink wrap technology because, I agree Vig, that making sure its all a continuos and closed model is very tedious and time consuming.

I had been looking at 3dcoat earlier, seems like it has some really nice tools. Not sure I understand voxel based tools though. What exactly is a voxel? As this model has to be submitted by the end of the week, I am not sure I have time to take a crash course. Is it a fairly simple process to convert it and change the density?

Mark Dygert

Think of a voxel as a pixel with volume.
Pixel a flat 2D square no height 1x1.
Voxel a 3D pixel 1x1x1.

Or think of this way: Green Voxels on Grey Pixels.

EarthQuake

I think he would be better off just brute forcing the screws into his mesh at this point, then trying to learn how to use a new program, using a new technique with limited time. But hey, who knows.

I say get on it in max, post less here and get it done! =D