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How Can ZBrush be Used for Low Poly Game Models Skinning?

ZBrush Usage Questions
#1

At first I thought that ZBrush would be a great asset for painting low-poly models. One such reason is ZBrush’s ability to create various UVTile Mappings. Setting up the UV mapping of a model can be a very time consuming process. But now I see even more problems with using ZBrush for this purpose.

No Overlapping Faces on the UV Map

Often models for real-time 3D games require you to use a smaller skin (512 x 512 or so) in order to save on video card memory. Even so, we want as much detail as possible. In order to maximize the detail on small textures/skins often areas will be halved and mirrored and then one half placed over the other so that they can both share the same part of the texture/skin. For example, someone may overlap half of a face or both sleeves of a shirt, etc. Well, you cannot have UV mapping like this in ZBrush or it can crash when trying to paint in Projection Master.

What this means is that you cannot add as many details as more geometry will be occupying the already crowded texture space.

Real-time 3D Requires Smaller Skins

Many real-time 3D projects require smaller skins. I work on projects where the skins must be 512 x 512. Using UVTile mapping I cannot get any real details as all faces of the model will get equal space on the texture. It seems that ZBrush and Projection Master are better suited for use with models that can use higher texture sizes.

Notes:

It seems that the UV mapping process cannot really be skipped for creating RT3D models. Therefore I cannot see that ZBrush will save me time in this area. Projection Master is not quite like painting on a 3D model, either, so I cannot see why I should opt ZBrush2 over good ol’ Photoshop for the painting of skins for low-poly models.

Overall, I love ZBrush more adding details to models. But my company is all about creating real-time 3D assets. So, help me to see how I can use this program effectively in my company. I am assuming that I am missing something and that my initial impression of ZBrush (as far as its use for RT3D) is incorrect. I would appreciate any advice that can be given.

Thoughts?

#2

I completely agree with what you’ve said. I was also hoping to use Zbrush as an effective tool for painting low-poly models, but… as you’ve outlined above, it has its weaknesses.

#3

its biggest strength this iteration is normal/displacement mapping creation. if you’re not using normal maps in your real time 3d, you can probably stick to your regular work path, but maybe find a use for z here and there.

unified uv and texturing is a pipe dream as far as real time 3d is concerned, I would follow the path the pros use - building models in a modeling package, texturing flat in photoshop or a paint package… and if you want you can use zb for bump stuff or ambient/ interesting texturing material to add to your arsenal

#4

From one aspect I see your point. Painting in ZB for low-poly games is not a desired process for now. It’s inability to mirror, flip, copy and paste efficiently is what ruins it for me.

However, you can still use ZB to help with certain things as far as painting goes. For one, you can easily fix seams in ZB. For another, you can use ZB as a guide for your photoshop texturing. Plus, using the bump map as a guide, you can paint a pretty good texture map.

But, to me at least, ZB greatest feature is the ability to create displacement/bump maps and normal maps. Most real-time games can utilize bump maps, and I for one can’t think of a better way to make a bump map than to actually model the geometry, and have that geometry as your bump map. So doing bolts, cracks, circutry, corosion, etc… can easily be achieved in ZB.

All my opinion of course.

#5

By the way, Tiles-based mapping also makes use of the AUVRatio slider. With this, you can specify the difference in size between the largest and smallest polygons in your model. For example, a value of 10 means that the largest polygon will receive a texture space that’s 10 times larger than the smallest polygon.

Also, one of the biggest advantages to Projection Master for texturing is that it takes UV distortions into account for you. In other words, you do not need to try and manually compensate for such distortions so that what you’ve painted flat looks good when wrapped onto the 3D object. Instead, you paint what you want to see on the 3D object and let ZBrush worry about what it looks like in 2D.

Regarding the size of your textures, what’s wrong with painting large so that you can get maximum detail and clarity, then resizing the finished texture smaller? This has been a huge advantage in any texturing I’ve done for other projects; I can’t see how it would be different for games.

One note regarding painting with Projection Master: By default it will smooth your model when you drop it to the canvas. This is undesirable if the model is not going to be smoothed by your game engine. If that is the case, then you should set the Tool>Display Properties>DSmooth setting to .01 before dropping your model to prevent smoothing.

#6

<BLOCKQUOTE>quote:</font><HR>By the way, Tiles-based mapping also makes use of the AUVRatio slider. With this, you can specify the difference in size between the largest and smallest polygons in your model. For example, a value of 10 means that the largest polygon will receive a texture space that’s 10 times larger than the smallest polygon. <HR></BLOCKQUOTE>

The only problem with that is a game model isn’t really going to be created or detailed like that… for example the head may not have very big polygons but it needs very high detail… what would be ideal is if you could make polygroups and choose the ratio of detail per group or something

same problem with a uniform size texture, with one 512x512 for example, little details will be destroyed over the whole thing, they’ll be big pixelation around eyebrows, lips, eyes, things of the nature that the player is going to be looking at so you want them to look the best… game developers use tons of tricks to get detail where it’s important and fudge it where it isn’t… that’s why the max + photoshop is a standard because it may not be artistic or intuitive, but it gives you the technical control you need to make everything work

#7

You can make your own groups, then export the GUV tiles into another UV editor and manually configure them to how you like. That way if the head needs more detail, scale the head GUV’s to be larger on the UV map.

#8

hmm, that’s true, unfortunately the engine I’m modding for, far cry, has grid line seams on the models when I use tiles, so I’ve pretty much given up on them. tried fix seams, etc…

#9

Yeah, there’s no telling what kind of issues you will get with the UV borders and the seams. Most times you can hide it with clever custom made maps, but GUV tiles, or any other automatic UV systems, really don’t work for certain situations.

I don’t know if there is an option to tell the engine not to allow for mipmapping, or blurring of any textures along the UV borders. I’ve found that turning this feature off usually eliminates seams. But that’s with software rendering. I don’t know if it will work for hardware.

#10

I am a game design student and zbrush has become a major player in my arsenel for low poly character modelling.
in my work flow zbrush has a major part in the modelling texturing and posing of player characters and static meshes. If anyone wants a quick tutorial on working in low poly with 3dsmax and zbrush i would be quite happy to go through my own personal work flow.
thanks

#11

you are welcome to provide your tutorial in the tuts forum.
http://www.zbrushcentral.com/zbc/forumdisplay.php?f=19

#12

Can someone please post a process for low poly modeling in zbrush