ZBrush AUV bad for games?

Pola

Several team members on project I'm in insist on using zbrushes auto uv methods to not bother with unwrapping their low poly meshes properly to save time. I am trying to convince them that it is not good performance wise for the game assets to be unwrapped liked this. That they should unwrap the low and transfer the zbrush painted textures via something like xnormal baking new maps to the unwrapped low.

The performance issue is all those islands add up to additional vertices right? Is there anything else I can say? Or am I wrong and this is a perfectly acceptable workflow to not unwrap properly?

cryrid

Yup, they'd be adding a lot of extra verts, especially if its one of the auto methods that gives every face it's own island instead of trying to at least pack them in groups. I lack the knowledge to know if this would also complicate tangent-based normal maps, but I wouldn't be surprised.

If they're lazy, you could at least try and push them towards using UV Master?

Pola

Yeah its the small packed tiles for uv's. They have a base mesh that zbrush makes the uv's for and the textures are baked into that automatic tile uv. Will UV Master unwrap the model without destroying their texture and sculpts? I'm not too experienced with zbrush myself.

cryrid

UV Master shouldn't harm the sculpt in any way. It can even automatically create a clone of the tool to work on instead (the UVs can then be copied and pasted to the original sculpt).

The existing texture can either be converted to polypaint and then converted back to a new texture in zbrush, and external programs like xnormal would most likely make quick work of this as well.

Noors

If ever you're using mipmaps, it will look like shit.
lots of extra vertices + no control over texture space + no padding + no way to edit it in photoshop = very bad idea.

Also i'm not very familiar with zbrush but i'm pretty sure you can unwrap your level 1 mesh in an external package then re-import it without affecting the sculpt.
So you're not constrained to zbrush for the unwrap.

claydough

Depends whether the ptex or prt realtime stuff is ready for primetime soon.

In which case I think ptex as levels of resolution would be used instead of mipmaps? The same way tessellation levels can be used to handle LOD geometry levels?

http://developer.amd.com/samples/demos/pages/AMDRadeonHD7900SeriesGraphicsReal-TimeDemos.aspx

The AMD Demo will only play on my Nvidia fermi hardware in demo mode without the shadow mapping . In their ptex demo it does not look like they attempt any crazy resolution.. however, the 2d maps ( prt slices? ) look alot like AUV to me?


(compared to a zbrush auv: if not the same, does not seem as if Pixologic has a huge leap to make in supporting a pipeline like AMD's demo? )

With New ptex support in Maya I am wondering if Zbrushes AUV can be leveraged in between pipelines in a ptex future?

Ptex and PRT Technology Preview


This technology preview, using OpenGL, demonstrates a way to implement Ptex (http://ptex.us/) in real time, making one of the latest film industry techniques practical for use in games. Ptex greatly simplifies the process of texture mapping and is already supported in a number of industry standard tools. Because Ptex also naturally eliminates seams, techniques such as vector displacement are easily enabled without need for manual seam fixup. Real-time Ptex per-primitive resolution control and the more efficient packing relative to traditional methods allow for higher quality textures, yet with very little computational overhead. Partially resident textures (PRT), accessible through an OpenGL extension, also allow for simpler Ptex addressing methods by enabling variable-sized slices in texture arrays, an addressing method which would otherwise be far too costly in memory usage

I am not sure how much resolution is possible but considering these slices are "hassle free" It sure would be nice if micro polygon levels of tessellation could be supported?

Packed Ptex gives each primitive its own little texture. Here we see the packed Ptex textures for Leo’s face, including color, ambient occlusion, and world space normal on the left, and specular coefficients and vector displacement on the right.
Vector displacement allows for more drastic changes in shape than standard displacement mapping. Here we show how the folded-up cuffs on Leo’s shirt are formed from a simple blob with just two levels of tessellation.
An ear is an example where artists often struggle to manually fix seams caused by standard displacement mapping. However, the vector displacement map for Leo was created from the high and low resolution meshes with just a few button clicks and no manual tweaking.