Which ZBrush features were the most beneficial to you?
The Alpha palette tweak tools were great to help fine tune the displacement effect I wanted for each alpha.
The "Trim" brushes were fairly new to ZBrush at the time I started working on the cliff, and they were great for achieving the blocky, monolithic look of some parts of the cliff.
But the HD geometry feature was key for pushing the amount of fine detail I could get from my 4K displacement maps. It was a bit frustrating at first having to work only on smaller parts of the model at a time, but once I got the hang of it and the ratio between the level of detail I needed vs. amount of subdivisions, things went faster. The cavity maps baked from the HD geometry looked pretty cool, too!
How did HD sculpting benefit you? How many polygons in all did the environment reach?
Yes, as I mentioned before, it was critical to use HD geometry. In my workflow, I would subdivide a cliff block up to two or three million polys and go HD subdivisions from then on.
My workflow would consist of blocking the low frequency, structural shapes of the rock-faces at 2+ million polys, making heavy use of the Trim brushes. Then I'd switch to my highest HD geometry level and project the 3K alphas to create the high-frequency detailed rock.
HD has some serious boundaries, and the toughest one for me was that you cannot preserve HD information if you import an HD-sculpted tool into another as a SubTool. That forced me to do some pretty clever cliff-splitting between ZBrush files to make sure I could sculpt a block in HD while having enough reference of its HD-sculpted neighbors to properly blend the seams between them. Yes, it sounds complicated, and it was pretty tricky.
Because the cliff was made of twenty blocks, it was impossible to have all of them subdivided as HD geometry into one single ZTool. HD geometry generates some heavy files. In fact, each cliff chunk file with all of its HD subdivision levels averaged 1.5GB.
In the end, I never added the total of the HD polys of all cliff blocks combined. But, as the average amount of HD polys per block ranged between 500 and 600 million polygons, doing some stupid math, we could crudely estimate that if put together into a single ZTool the whole cliff would have about 10 billion HD polygons in ZBrush.
Did you only create displacement maps with ZBrush, or did you create textures or other assets as well?
I did export cavity maps from the HD geometry, which we used in the rock shader, but the cliff relied mainly on the displacements for the final renders.
We had other minor assets for Immortals in which we used ZBrush. The most critical one was the hawk that appears in a few shots. It was initially bid as a tiny bird seen at a distance, but the clients kept asking to bring it closer and closer to camera until we had a hero shot of the hawk almost filling the screen! Our initial low-res bird asset had to go through some last minute "revamping" to handle the close-up. We added more feathers, a refined animation rig and better UV coordinates. Marco Menco did a lot of ZBrush sculpting on that guy to give the feathers some nice displacements in order to break up the bird's silhouette and specular highlights.
How long did the Immortals project take?
The project as a whole took just over a year.
Is there anything you'd do differently, looking back on the project?
We made a decision to push the envelope of how much we could get done with ZBrush in terms of detail, before switching to matte-paintings for the cliff close-up shots. Later in production, I would come to regret the decision of building the cliff with only 20 pieces, wishing I had split it up even further. That would have been greatly beneficial to some extreme close-ups we had.
That being said, creating even more pieces would have been too great a sculpting challenge within the team constraints and deadlines we had. The close-ups were masterfully handled with matte paintings and projections.
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