ZBrushCentral

How much detail and is their math? [Answered]

ZBrush Usage Questions
#1

I was wondering if there was anyway to mathematically figure out how much detail can be projected onto a 1)normal map and 2) displacement map? In other words if I have a 1000 tri limit on an object how much can i subdivide before I won’t be able to project all the detail to each map, assuming the low poly base mesh is made very well. Is their at least a rough number?

I feel this information could be crucial to many if there a way to figure it out. If I know I can only get 1 million polys to project onto a 1k mesh then that would be nice to know for each accompanying map. Also is there any other factors that come into play other than how the base mesh is built?

#2

This greatly depends on the efficiency of the UV. Assuming a 1K map is 1024x1024, you have a million poly limit. But that assumes that your UV covers the entire availavbe UV space, which s unlikely. Way would be nice is a tool that ud tell you how much of your UV pace was in use, as. Percentage. Then you could coud just know, r example 80% usage, gives me around 800k polys, in this example. (Sorry, should have qualified this with an ‘I think’)

#3

As Gordon Robb says, it depends on the UVs and the size of map you are using. If you use UV Master then perhaps only 50% of the available map will be used, whereas if you use automatic mapping such as PUV in the Tool>UV Map sub-palette then 90% or more of the map will be used. You can get a rough idea by looking at a map generated in the Tool>Texture Map sub-palette, such as by pressing New From UV Check. The gray area is used and available whereas the black area is unused and unavailable.

Once you’ve decided on the percentage of map used you would multiply that by the number of pixels in the map (which gives a theoretical maximum number of polys). The number of pixels for each map size are (approximately):

1024 x 1024 = approx 1 million
2048 x 2048 = approx 4 million
4092 x 4092 = approx 16 million
8192 x 8192 = approx 64 million

For high resolution detail you can allow one pixel for each polygon (though note that some UVs will assign more than one pixel per polygon). So for UVs that cover 50% of the map, a 2K map would give you detail from 2 million polys and a 4K would give you 8 million.

(for a plugin, see below)

#4

I made a little plugin to give you the info. You can get it here:
http://www.zbrushcentral.com/showthread.php?172391-Useful-small-ZScripts-and-Macros-for-ZBrush-4R4&p=1011698&viewfull=1#post1011698

#5

Interesting. So the UV is the one that dictates the amount of polys available to project? So how much does the base mesh’s amount of polys play a role?

#6

very cool! Doesn’t work for ZR4 unfortunately :frowning:

#7

The base mesh and the UVs are linked. UV mapping is a set of coordinates that map a 2D image (a texture map, displacement map etc.) onto a 3D object (the base mesh). Put simply, it’s the UVs that allow the image to be displayed correctly on the 3D mesh, a bit like wrapping a sheet of paper (2D) on a parcel (3D).

Your base mesh can have any number of polygons but it’s generally better to keep to a few thousand or tens of thousands. That way operations like UV mapping are easier and take fewer resources.

For sculpting you can then subdivide the base mesh as much as you need (or your system can handle). But if you plan to export your model along with a displacement map etc. for rendering in another app then that is where you need to worry about UV mapping and the map size, so that you get all the hi res detail ito the maps.

#8

I understand that. The problem I usually encounter is having too little amount of polys on my base and not being able to project the detail, even with a decent sized map (2k). I’m going to try to keep a rule of thumb for the amount of geo assuming I have around at least 50% uv space taken care of Also that zplugin is great, but I’m currently on ZR4.

#9

Update to 4R5 - it’s free to registered users.

#10

yea will do :slight_smile: