Plugins + Scripts [Experimental] AlternativeHairPhysics

Small update. The jitter added to soften self-shadows was interfering with the hair texture. It's default off and tunable now.

• Added voxel-based volumentric self-shadowing. It eats into perf, but usually worth it.
• A moderate performance boost from better parallelization of some geometry calculations
• Fixes for multiple hairs (Still need a separate instance of the plugin per - sorry)

I've revamped how spread and alignment works. The various spread sliders were removed. There are now four primary controls:

• Root and tip radius - the spread at the root/tip
• Root and tip skin alignment - how much the root/tip follows the skin

Before, sub-hairs were always rendered radially outward from the main simulated hair strand. This meant that hair that flat against the skin (left) would render like macaroni that didn't follow the skin at all(middle). Now you can align the root and tip, allowing for a more natural spread (right). This is most visible for body hair or fur, but also makes the scalp region on regular hair look much better.

The other major fix people might notice is a more correct disable logic that no longer leaves a phantom hair or perf hit. Otherwise there are a bunch of small things that I've forgotten already.

Also fixed tip curl.

• I tore out the Impostor render mode. It's Compute-only now as that seems to be the better long-term bet
• Tweaks to the k-buffer that should result in significantly better performance at K=4 (default)
• Immediately ate into the perf improvement with some occlusion fixes, but should still be a net win
• Added sliders for tip curl, which is meant to break up the unnatural smoothness of the hair

I managed to increase the size of the k-buffer - allowing for better anti-aliasing. I also added an Analytic Coverage toggle, which makes the AA cheaper.

The end result is better-looking hair for more or less the same performance

Before

After

I've built a new render mode - Compute. Impostor rendered hairs on a bunch of transparent 'cards', which VAM rasterized pixel by pixel even though they were mostly transparent. Compute instead has one card, which is rasterized manually.

The end result is a huge improvement in FPS - better than stock VAM hair even at max settings (at least for me). The downside is bugs. Lots of bugs.