This guide will take you through the process of creating realistic real-time content for your characters.
by Alex Borre
Alex Borre is a 3D Artist from Chicago. He has worked in the game industry for 5 years now, including work on AAA game titles, VR/AR experiences and pinball machines.
Choosing the right apparel for a character can be a daunting decision to make. Whether you’re creating a futuristic sci-fi soldier, a fantasy adventurer, or just your average businessman; it is important that your character’s clothing reflects their environment to add a level of believability and immersion to your project.
Modeling clothing can be very difficult, and hand sculpting realistic cloth folds and wrinkles is something that even the best sculptors struggle with. In this tutorial, I will be utilizing cloth simulations in Marvelous Designer to make this process more manageable. Combining the use of cloth simulation and the powerful sculpting tools inside ZBrush, there are endless limits in terms of what we can create! In this guide, I will be using these tools to create a post-apocalyptic style trench coat.
It’s important that the clothing we create also fits our character model nicely and is rigged properly so that the character’s mesh doesn’t clip through during animation. Reallusion’s Character Creator (CC) has great tools for preventing these problems, but the best place to start is with the proper skin weights.
This guide will take you through the steps I took in creating clothing assets for Reallusion Character Creator’s Post-Apocalyptic Asset Pack.
Step 1 – Planning your Model
Before we immediately jump into production we must have a very clear idea of what it is that we want to create! It’s important to first gather references. The cloth creation process is going to begin with a simulation in Marvelous Designer. Our work in this software will be very much like sewing a garment in real life, so gathering references from real life is crucial. I gather as much reference as I can for each asset, finding alternate angles, designs, and inspirations that I can pull from while working. With so many online clothing assets, it’s very easy to find references for sewing patterns of the type of garment you are trying to create. These will be helpful materials when you’re beginning your simulation.
Step 2 – Conceptualizing your Ideas
Regardless of where your abilities may be with 2D art, it’s a great help to have a concept to work from. The concept combined with your reference will be your guide to the final look of your model. Remember that the concept can go beyond just an image too! Taking textual notes of what qualities you want your garment to have, or descriptions of its quality and functionality can go a long way. Without a concept, you may find yourself getting lost or stuck along the way.
Step 3 –Blocking Out your Garment
Bring your Character Creator mesh into Marvelous Designer as an Avatar, and begin laying out your garment according to your reference material. It’s important to start simple and get the measurements right. Keep the particle distance high so that you can work with the model in the 3D view as you go. This first pass at the simulation is essentially the foundation of all of the rest of the work you’ll be doing in Marvelous Designer, so it pays to be precise! Take advantage of the ability to work symmetrically.
Step 4 – Adding Layers
Once you feel like you have a good foundation, the next step will be to start adding secondary details. Now you’ll want to add layers of clothing that might be on top of the first layer like pockets, belt loops, and folded-over areas.
Step 5 – More Layering
It’s important to get the garment to a complete a state as you can inside Marvelous Designer, before bringing things into ZBrush. The more detailed your garment is, the better the simulation will end up being. Complex articles of clothing can require a lot of time and effort in the simulation process, but when it’s done well it can make the rest of the process quite painless!
Step 6 – Assigning Materials
When you have your pattern laid out, then it’s time to add materials accordingly. You want to make sure to assign fabrics properly to each piece of clothing. The preset fabrics in Marvelous Designer are generally enough to get a nice simulation. You want to make sure that you have a leather fabric to your leather patterns, cotton to your cottons, etc.
Step 7 – Final Simulation
Once your pattern is laid out and the materials are assigned, it’s time to create the final simulation. Set the particle distance on your garment to a low number to get a high-resolution simulation, and set the Simulation Preset to “Complete” under the Property Editor menu.
Step 8 – Exporting to ZBrush
With the simulation complete, you are ready to bring the model into ZBrush. There are a few export options in Marvelous Designer to be aware of. I always export a thin, unconnected mesh as this will give the most control within ZBrush. I also prefer to have the object exported as a single mesh. Multiple meshes work too, but I like to be able to separate pieces out manually if I find that necessary.
Step 9 – Cloth workflow in ZBrush
Cloth simulation can produce a pretty high level of detail, but there is still work to be done to get the cloth looking more realistic. The simulation creates folds based off of a simulation on a character in a single pose but does not account for wrinkling and other details that would accumulate on an article of clothing while someone is wearing it, such as the harsh folds that occur around the elbow or armpits. These details will be added in ZBrush as well as buttons/hard surface elements and touched up seam lines. ZBrush has a great set of tools for creating thickness for our model and creating a nice edge loop around seams for easy modification.
Step 10 – Preparing the Mesh
I’ll start the cleanup process by separating out the cloth meshes into the different material types I had set up inside Marvelous Designer. This allows me to detail each material type simultaneously. ZBrush’s Polygroup -> Autogroups make selecting and separating the different meshes easy. Also, if you weren’t able to export the mesh from Marvelous Designer as quads, then you can use ZRemesher to quadrangulate your mesh. Be sure to use very high resolution so that you don’t lose detail.
Step 11 – Adding thickness via Panel Loops
Panel loops are a great way to add volume to your mesh. Not only does it give you control over the thickness, it will also create a polygrouped edge loop around the perimeter of the cloth. This polyloop will be very important in adding details along seam lines. Having a separate polygroup along the edge works really well with some of the other ZBrush’s tools such as ZModeler and NanoMesh.
Step 12 – Detailing Hems and Seam Lines
How the seams are detailed depends on how your particular garment is sewn together. For this particular garment, I didn’t worry about getting fine details at the seam level, but it was important to have an extrusion along the border to create the look of a hem along the cloth’s edge. To achieve this effect I used Zmodeler along the edge loop created by the previous steps. The resulting extrusion creates yet another polygroup that can be extruded again to create a little seam line effect across the new mesh. Additional details such as seam threads can be added using alphas in a later phase, or using nanomesh along the new polyloops.
Step 13 – Hard Surface Elements
At this point, I like to add the hard surface elements such as buttons, clips, zippers and others. I do this now because these pieces can often influence the wrinkling around an article of clothing. Before getting into custom wrinkle details, it is important to know what will be influencing the cloth. For example, you will very rarely see a harsh wrinkle go perpendicularly through a zipper, since zippers are very stiff. It’s a minor detail, but getting things like this right can be a nice touch!
Step 14 – Sculpting Wrinkles
After I’ve added thickness and seam details to my mesh, it’s time to add in additional wrinkles. It’s especially valuable to go back to your reference at this point to try to find qualities you’d like to replicate. Some fabrics like satin or silk may not have too much surface detail or wrinkling. Whereas stiffer fabrics such as the ones I’m using for this coat will have developed many wrinkles over time. I’ll start by dragging wrinkle alphas over my mesh to get some basic surface detail. Once that’s done I’ll hand sculpt some more prominent wrinkles. I like to use the clay brush for softer wrinkling, and the dam standard for some harsher wrinkles such as the inner elbow or behind the knee.
Step 15 – Finalizing in ZBrush
I generally will spend a long time in this sculpting phase of the project. A high-quality high-res mesh can go a long way in the production of an asset. Keep in mind that much of the fine surface-level details such as the threads of the fabric are better handled during the texturing phase, so I tend to not go that far in sculpting.
Step 16 – Low Res, UVs, baking, Texturing
For this tutorial, I won’t be covering these subjects in detail. I go through this process mostly the same way I would for any other 3D asset. For cloth, it’s important to remember that the clothing will be deforming the same way a character would so it will need a similar edge flow and extra edge loops around areas of high deformation. Also, when UVing, it’s beneficial to have the UV islands facing directly along either axis. This way when adding tillable textures the lines of the fabric will follow along the mesh in a more realistic way. My preferred software for texture painting is Substance Painter. With the right exported maps, Substance Painter can make the texturing process pretty quick and efficient!
Step 17 – Rigging
To set up the rigging process, bring in your low-res cloth asset into the same scene as the rigged character you are working with. If you plan to bring this asset back into Character Creator, you’ll want to use a base character mesh FBX file with motion animation exported from Character Creator. Bind your cloth asset to the character skeleton. Select your rigged character mesh, and then your cloth asset. Go to Skin -> Copy Skin Weights. Maya will do it’s best to have your cloth asset weights match the weights of the character. Either use or make a range of motion animations to test the skin weights as you work. This is usually a good place to start for any asset, but there will be issues that need to be resolved!
Step 18 – Troubleshooting Weights
Editing skin weights can be a frustrating process, but if you’re careful and thorough it can be relatively painless. I like to set up my UI so that I can see the whole skeleton in one view, which is where I’ll be selecting bones using the right-click menu. I also use a second viewport to navigate around the mesh to do my weight painting. There are a few common issues with weight transferring. If your skeleton has any bones that are directly on top of each other, then Maya will sometimes mistake the two bones and weight a piece of the mesh to the wrong one. An easy way to solve this problem is by entering the Paint Skin Weights menu, locking ALL other bone weights except for the bones you’re transferring to and from, and flood filling a weight value of 1 onto the desired bone.
Step 19 – Painting Weights
Another common problem area is around the shoulders and armpits. The clothing may do a good job following the character mesh, but often times the edges don’t deform very well and will need to be fixed through weight painting. To avoid headaches while painting, keep ALL influences locked so that you aren’t trying to modify them. Maya will sometimes automatically assign influences (while smoothing weights). If your weights are all unlocked then you can get some really undesirable results. For this reason, try to stick with using Add and Smooth operations within the painting tool, rather than using Replace or Scale.
Step 20 – Fixing Issues using a Proxy Mesh
Sometimes you may find particularly problematic areas that just refused to be fixed with just painting weights. This can happen if your mesh has a dense or complex geometry in a high-deformation area. A good way to deal with problem areas like this is to create a proxy mesh to transfer the weights from. To do this, create a low-resolution mesh that has just enough edge loops to represent your asset while still maintaining simple geometry and edge flow. Bind and transfer your weights onto this new mesh, and fix the problem areas on this simpler geometry, then transfer the weights back to the problem areas of your asset.
Step 21 – Finalizing your Asset in Maya
Once you’ve gone through the weight painting process, go through the range of motion animations a few times to be sure that the cloth is deforming well. Watch for any intersecting of the character mesh and cloth mesh, and paint weights to fix these problems as you see them. The methods described above should be useful for any problems you may encounter. With a bit of work, you can achieve a nicely weighted cloth asset.
Step 22 – Importing your Asset into Character Creator
If you’re working off a Character Creator mesh, then your Maya scene should include a few meshes labeled: “CC_Base_…”. Select your asset mesh as well as these CC meshes and export them as an FBX. Inside CC go to “Create -> Cloth, Hair, Acc…” and to your exported FBX asset, and the .fbxkey file that was generated when you originally exported the Character Creator base mesh.
Step 23 – Setting your Cloth Layer
In order for your cloth to properly layer with other default assets inside Character Creator, it must be set to the proper cloth layer. Reallusion’s website contains documents describing the proper layer number per type of clothing. This should be referenced in order to select the proper layer. Texture maps should link automatically, though you may need to switch from a Traditional to a PBR material if desired.
Step 24 – Exporting an iAvatar
While inside Character Creator you can add additional assets to your character, either from the Reallusion’s default library or from assets you’ve found or created yourself. For my character, I’ve decided to give him a pair of jeans and a shirt to wear under my coat. Once you are satisfied with your character, go to File -> Export -> iAvatar. Now, this file can be imported into iClone where your character can be brought to life!
Step 25 – Animate with iClone
In iClone, go to “File -> Import” and navigate to your Avatar file. With your character successfully imported, you will be able to apply iClone animations to your character and see your custom asset in motion.
Tip 1 – During production, take advantage of symmetry whenever you can. Whether you’re laying out garments, sculpting details or painting skin weights, mirroring the work will take half the time. Symmetry can always be broken at a later time.
Tip 2 – When painting weights in Maya, holding right-click on a bone in the viewport allows you to select influences much quicker than navigating through menus or outliner.
Tip 3 – The Hammer tool in Maya (Skin -> Hammer Skin Weights) can be your best friend for fixing per-vertex weighting issues.
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