For a little while I have been using Houdini topo transfer tools instead of Wrap 3. Not saying that I can fully replace Wrap3 but for some common and easy tasks, like wrapping generic humans to scans for both modelling and texturing, I can definitely use Houdini now instead of Wrap 3.
Wrapping generic humans to scans
This technique will allow you to easily wrap a generic human to any actor’s scan to create digital doubles. This workflow can be used during modeling the digital double and also while texturing it. Commonly, a texture artist gets a digital double production model in t-pose or a similar pose that doesn’t necessary match the scan pose. It is a great idea to match both poses to easily transfer color details and surface details between the scan and the production model.
For both situations, modeling or texturing, this is a workflow that usually involves Wrap3 or other proprietary tools for Maya. Now it can also easily be done in Houdini.
First of all, open the ztool provided by the scanning vendor in Zbrush. These photogrammetry scans are usually something around 13 – 18 million of polygons. Too dense for the wrapping process. You can just decimate the model and export it as .obj
In Maya align roughly your generic human and the scan. If the pose is very different, use your generic rig to match (roughly) the pose of the scan. Also make sure both models have the same scale. Scaling issues can be fixed in Wrap3 or Houdini in this case, but I think it is better to fix it beforehand, in a vfx pipeline you will be publishing assets from Maya anyway. Then export both models as .obj
It is important to remove teeth, the interior of the mouth and other problematic parts from your generic human model. This is something you can do in Houdini as well, even after the wrapping, but again, better to do it beforehand.
Import the scan in Houdni.
Create a topo transfer node.
Connect the scan to the target input of the topo transfer.
Bring the base mesh and connect it to the source input of the topo transfer.
I had issues in the past using Maya units (decimeters) so better to scale by 0.1 just in case.
Enable the topo transfer, press enter to activate it. Now you can place landmarks on the base mesh.
Add a couple of landmarks, then ctrl+g to switch to the scan mesh, and align the same landmarks.
Repeat the process all around the body and click on solve.
Your generic human will be wrapped pretty much perfectly to the actor’s scan. Now you can continue with your traditional modeling pipeline, or in case you are using this technique for texturing, move into Zbrush, Mari and or Houdini for transferring textures and displacement maps. There are tutorials about these topics on this site.
Transferring texture data
Import the scan and the wrapped model into Houdini.
Assign a classic shader with the photogrammetry texture connected to its emission color to the scan. Disable the diffuse component.
Create a bakeTexture rop with the following settings.
Resolution = 4096 x 4096.
UV object = wrapped model.
High res object = scan.
Output picture = path_to_file.%(UDIM)d.exr
Format = EXR.
Surface emission color = On.
Baking tab = Tick off Disable lighting/emission and Add baking exports to shader layers.
If you get artifacts in the transferred textures, in the unwrapping tab change the unwrap method to trace closest surface. This is common with lidar, photogrammetry and other dirty geometry.
You can run the baking locally or on the farm.
Take a look at the generated textures.