Skinning Assetto Corsa Cars from Nothing using Mudbox and Photoshop

This Tutorial was originally posted over on the simracingsystem.com forums where I do all of my skinning. I was constructing it AS I was learning the process, so obviously some of this is going to be "not the best way" to do certain things. I was going to make a post just linking the original tutorial, but after asking permission to the folks here at RD, it was suggested that I just post the tutorial in its entirety here! That said, let's get started!

NOTE: I have added notices before or during the parts where it is SRS specific, like making sure your skin is under 10MB (a limitation of the SRS Skin Transfer App used to automatically share custom skins just before races start). Follow the red instructions so you aren't doing extra work where you don't need to!

Software Used
The Goal
Since it is almost the end of the current season and I don't know what cars are going to be used next season, I figured I'd learn on something that I figure will EVENTUALLY come up. So the McLaren 650 GT3 is what I'll be doing. The goal is to replicate my typical Red/Black two tone design, complete with a skull on the hood using the most efficient means... rather than just fumbling around with a wireframe texture in Photoshop like I have been doing.

Disclaimers
  • I'm not a professional artist. I have a background in graphic design and some 3d modeling but make no claims to know the best way to do any of this stuff. This is just what I've learned jumping in head first.
  • Also, Mudbox crashes. A lot. Save often!

Extracting 3D Model
I started by using a program called 3DSimED3. Unfortunately it only has a 20 day trial, and today it ran out. Normally in this situation I would just purchase a licence and call it a day, but I was curious if there was a better way to just get a 3D model out of the .kn5 files that Kunos includes in a normal installation of Assetto Corsa. My googling lead me to this youtube video: Assetto Corsa KN5 Converter & Download

I was unable to find the origin of kn5conv.exe, but I ran a few scans on it and it turned up nothing, so I gave it a try. Works great. Here's how _I_ would recommend extracting the model (as opposed to how the youtuber above does it):

  1. Create a Workspace for your new skin outside of your Assetto Corsa file structure. Here's mine: S:\GameFiles\AssettoCorsaStuff\cars\ks_mclaren_650_gt3\workspace
  2. Copy the mclaren_650_gt3.kn5 file from your Assetto Corsa installation into this folder (you can find it here: ...\Steam\steamapps\common\assettocorsa\content\cars\ks_mclaren_650_gt3.kn5)
  3. Place an instance of kn5conv.exe in your workspace folder.
  4. Drag the KN5 file onto kn5conv.exe and watch the magic happen.
The result is that in your workspace folder you will now have a number of file types that can be understood by a number of 3D software packages, such as Mudbox and Blender. I gave Blender my best shot, but couldn't figure it out and there was not a good tutorial I could find that would clue me into how it works. I did find one that was enough help so that I could get going in Mudbox, so that's what I'll be doing.

If interested, here's the youtube video I found that got me going:

Cleaning Model For Painting
Once you have an .FBX file for the car you want to paint, you can import it into Mudbox.

  1. Open Mudbox.
  2. File>Import...
  3. Navigate to your workspace folder and import mclaren_650_gt3.fbx
  4. Save the scene as a .mud file (mclaren_650_gt3.mud) in your workspace folder.
tW27zHe.png


This is ALL of the geometry and a bunch of other nodes/objects that you will not need for the purposes of creating a livery. So we must now delete all of the stuff we don't care about. This will speed up performance within Mudbox, as well as avoid Mudbox wanting you to add additional materials every time you attempt to paint on a different mesh. In other words, we want to avoid painting on the windshield when what we want to do is paint on the car's body. Here's what I did to go through everything:

  1. Change to the Object List.
    PFRDqcNl.png

  2. Hide everything in the Object List
    vK0Fq6Cl.png

  3. Show only Geometry
    DWA09AHl.png

  4. Switch to Object Selection, and turn on Mirror on the X axis.
    O9lP6tQl.png

  5. Select geometry in the scene view that you know you will not be painting. Windows, tires, brake discs, windshield wipers, whatever. All that should be left are the panels of the car you want to put your design on.
  6. Save your .mud file. You may want to save it as a different .mud file than the original, in case you realize later you deleted some part of the geometry you actually wanted!
The end result should look a bit like this:

cNmg23N.png


...continued next post...
 
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Yep doing ACC skins.

Only way around I can find is to select all with wand on that layer and select inverse and delete seems to get rid of the ghost section just really frustrating why it does it as a right pain when I want to add strokes etc
 
why it does it as a right pain when I want to add strokes etc

You just need to play with the select tolerance. But I have no idea about your competence with photoshop/mudobox etc. so I may be telling you some obvious things you are already doing.

Anyway, when I'm erasing paint in mudbox with my settings the paint gets erased completely. I also export only one layer at a time. I.e., right click -> export channel to psd.
 
Have tried different tolerances in photoshop still no change you say you don't have this issue in mudbox could you look at your settings and let me know as be interesting to see what I have different.

I can do that when I have access to my home machine.

Anyway the magic wand tolerance should really be enough, make sure you only use the current layer and then use "transparency" or if you choose rgb value/color/luminance make the tolerance to be strict enough. I see no reason it would choose color values outside of it's limits that way.
 
If I recall, changing the tolerance didn't help. It is as though there's hidden data on the layer that are considered the same as the main pixel definition being clicked on with the wand, so clicking on the "painted" section selects the ghosted pixels, and clicking on the transparent section outside of the ghosted section selects everything but the painted section and ghosted area, making inverting the selection also not work.
 
If I recall, changing the tolerance didn't help. It is as though there's hidden data on the layer that are considered the same as the main pixel definition being clicked on with the wand, so clicking on the "painted" section selects the ghosted pixels, and clicking on the transparent section outside of the ghosted section selects everything but the painted section and ghosted area, making inverting the selection also not work.

I haven't used photoshop for a while as I changed to gimp/paint.net and paint shop pro. And in those programs I haven't had such a problem, although I did not have any problems with Photoshop either... My use case can of course be different and not manifest the problem at all.

So it may be a problem mudbox writing a broken psd file or something.
 
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It's strange if I select the pattern direct with wand it picks up ghosted part but if I alt select in layer tab it selects correct shape from.mudbox and allows me to invert and delete ghosted part It's a work around that I feel will have to live with.
 
It's strange if I select the pattern direct with wand it picks up ghosted part but if I alt select in layer tab it selects correct shape from.mudbox and allows me to invert and delete ghosted part It's a work around that I feel will have to live with.

Maybe you could put the psd file somewhere so we could see ourselves what is causing it.
 
even if I make my stencils at a high res and my fall off on the brush up full I'm still getting soft edges on what ever I paint ?
any fix for this I have a crazy build coming up and I don't know if I can be bothered sorting all edges in photoshop

@Russell Sobie just wondering if you have the same issue
 
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