Is it possible to increase the size of the “Create Alpha”. I currently get a 1024 but I would like to make a 4k or 8k if possible.
On the PC version of ZBrush all map generating functions use the currently selected texture or alpha to determine the dimensions of the next generated texture or alpha. There are exceptions such as the Multi Displacement plugin that allows you to define the dimensions and the Mac version of ZBrush has a more streamlined approach (as far as I recall).
So, to change the size of the Tool > Masking > Create Alpha generated map you can either import an alpha of the desired dimensions or create a texture in ZBrush and convert that into an alpha. Then press Create Alpha while the alpha with the desired dimensions is selected.
Not the most ideal workflow IMO but luckily it can be automated with a Zplugin. I’ll post such a plugin a little later.
Hope that helps.
Here is a simple plugin that will allow you to set the desired size and then create an alpha of that size based on the masked areas of the currently selected subtool.
Extract the .zip file below to the ZStartup/Zplugs folder of your ZBrush 3 installation. The next time you start ZBrush you will find a Sintilation subpalette under the ZPlugin menu.
Note, although using the plugin you can set the size to 8192 (8K) it will only create an 8000 alpha, which is a limit set by ZBrush.
In case you are interested the .txt file below shows the script code.
The Tool>Masking>Create Alpha button takes the currently selected Texture size as the size of the alpha. If no texture is selected then the default size of 1024 x 1024 is used.