Maya to Mudbox workflow:
- Add supporting edge loops to your low poly model in Maya
- Select ‘Export Selection’ and then export your asset as an FBX at point 0,0,0
- Import this into Mudbox or ZBrush
- Duplicate your model. Hide one of your duplicates and save this for later so you can bake your high poly model onto it
- Insert more polys and add detail using layers
- Once you have finished adding detail to your high poly sculpt, select ‘UV Maps and Tiles’, ‘Extract Texture Maps’ and ‘New Operation’. Select normal map and select your low poly model as your Target Mesh, and your high poly model as your Source Model. Change the ‘Method’ from ‘Ray Casting’ to ‘Subdivision’. Finally, select where you wish to save the normal map before clicking ‘extract’. Hide the high poly version to see the low poly mesh
We use this workflow for optimisation. Baking allows for assets to have the appearance of being high poly whilst not requiring much space or time to render
LEFT: High Poly Sculpt: 2187264 polys (not optimised)
MIDDLE: Low Poly Bake: 534 polys (optimised)
RIGHT: Normal Map
Medieval Asset Project
For my medieval asset, I have chosen to create a Hungarian shield, which was used by Christian and Islamic horsemen in the 16th century and had an elongated upper edge to defend the user from saber cuts while the slim steel point allowed for offense.
- rectangular with a rounded-off upper right corner and of rounded horizontal section.
- made of wood, the exterior covered with gesso (a white paint mixture consisting of a binder mixed with chalk, gypsum, pigment, or any combination of these. Dries hard, making the surface more stiff.) and painted vermillion with a white border decorated with a geometrical vegetal scroll, across the centre is a white band
- painted with an inescutcheon of vermillion with a black sun with gold rays, a continuation of the white band and crest in the form of a crow in black with white flashes standing on a black scroll.
- inside is painted white with a vermillion border and black spiral scrolls outlined in vermillion. At the front are two original buff leather straps joined by a spirally-bound leather thong forming the front hand-grip.
- centre rear is another nail retaining the base of two buff leather straps. Above the lower hand-grip are two additional nails for straps, now lost. Each of these nails originally had a large triangular washer on the outside, all but one of which survive.
- Could also be made from steel. Height 82/45cm, width 39 cm (my low poly model was made to this scale)
Using these reference images I was able to create my low poly shield in Maya:
Once I had completed the UVs for my model and ensured it was placed at point 0,0,0, I exported it as an FBX and opened it in Mudbox. From here, the first thing I needed to do was make a stencil which was similar to the metal that my reference is made from. To do this, I downloaded a stencil from the Pixologic alpha library (https://pixologic.com/zbrush/downloadcenter/alpha/#prettyPhoto) and imported this into Mudbox.
Next, I increased the subdivisions on my shield to 6 to make the stencil look good. When applying the stencil I used the Wax tool with a brush size of about 7 and strength of 5
I essentially repeated this process when adding the flower but in Photoshop (flower stencil downloaded from https://www.vexels.com/vectors/preview/156235/monocot-flower-icon) I swapped the black and white sections of the flower because white goes out and black goes inwards
Below are some screenshots of my high poly model:
From this high poly model I was able to make a normal map to bake onto my low poly model ( UVs and Maps -> Extract Texture Maps -> New Operation) but my initial map was bleeding on the edges and had random patches on it:
- To fix this went back into Maya and adjusted the edges/ UVs – cut and unfolded them to reduce the amount of stretching around the edges, resulted in the following UVs:
- When selecting my export options for my FBX, selected smoothing option. This resulted in a hard edge on my normal map as a result of selecting this option despite smoothing down my model in Mudbox. To resolve this, I selected soft light on all my model in Maya, exported it with smoothing and tried again which worked better.
- Model was smoothed down in Mudbox a bit too much making the mudbox curve more curved than the low poly, making corners stick out
- Going to adjust certain aspects in Photoshop
- Retopology – some people use a different workflow where they begin with a high poly sculpt and then in Mudbox they select ‘Retopologise’ and create their low poly from the high poly. Advantages of using this workflow are that you know that your high and low poly won’t have the potential to be drastically different
- Initially the flower looked stretched on my bake
- Combine the two normal maps together in Photoshop – place the ones for the rings on top. Have to be careful it doesn’t make things too flat when doing this.
- When adjusting normal maps in Photoshop people usually use this sphere as a guide for the colours in the different directions – red colour for the X axis, green for the Y, blue for the Z axis
- In Maya you can retopologise by making the low poly a live object and selecting the quad draw tool. This allows you to manually place your polys
- Slightly adjusted the UVs in Maya. Imported the low poly in again as it wouldn’t differ too much from the high poly
Normal map from exporting the FBX with smoothing groups (but not with the soft light option applied) – needed to redo this because the hard edge on the back was printed onto the normal map
Normal map with smoothing groups and soft light. Insides of model look alright on model but the edges still need adjusting in Photoshop – use the clone stamp tool etc. Can either adjust the curve in Maya which points out on my low poly or just adjust the normal map in Photoshop
When adding my shield into Mudbox again, it appeared with the same error I had encountered before but this time actually showed what the issue was I seemed to have removed an edge loop but the vertexes were still there. I deleted these vertexes and to further retain the shape of my model decided to add the actual edge loop in again which removed the error
Set a Mudbox material (brown) in place of the grey lambert
Sometimes you’d make two sets of rings to add to try and make them look more different – less obvious you’ve duplicated it
‘Break connection’ allows you to remove a material
Next I imported a plain FBX of my shield into Unreal and along with my normal map, created an albedo map, an ambient occlusion map and a metallic map for my shield using Photoshop
Next I added these maps to a new material which I then added to my shield
With this done I then created a cube and added the following material to it to give me a black background for my high resolution screenshot
High Resolution Screenshots of my shield:
This project has introduced me to the concept of baking in Mudbox and adding metallic, albedo, ambient occlusion and normal maps to my model in Unreal where I can then adjust the lighting to take a presentable screenshot.
Although my final outcome was alright, I can see a lot of room for improvement; I believe my main issue was making my original low poly model too low poly to the extent that my final high poly model in Mudbox was quite a lot different in comparison, meaning that when it came to baking my texture, some hard edges still remained.