Basically, it makes it so the collision is much more precise.
I’ve wanted this for SOOOOOOOOO LONG! THANK YOU ROBLOX!!!
It increases collision precision at a cost of performance.
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Does ingame CSG support this yet? I tried implementing this into my project in the second parameter of Part:SubtractAsync(_, Enum.CollisionFidelity.PreciseConvexDecomposition) but it seemed like it was always using Default no matter which value I passed.
I am so happy about this! I can finally make terrain in Blender and actually walk on it! 
I fixed it now it was a bug I basically had to redo all my settings after turning it on.
I remember in early 2018 trying to make working gears with unions. I wish this feature was added back then!
Here’s an interesting issue. This triangle terrain test I did has a very odd and incredibly inaccurate collision set, which seems to be an artifact of some of the approximations.
The result is not much better than Default. Here’s the mesh ID for testing: rbxassetid://4957760322
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This is a great feature. Better than I expected! Wonderful tools for all Developers. 
This is now Globally enabled, btw.
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I’ve been having some issues with the new collision fidelity. It seems to be not as precise on lower-poly meshes. Will this be improved in the near future or will it simply stay that using Default will be better for lowpoly meshes? Having this new rendering collision fidelity seems counterproductive considering the ROBLOX engine doesn’t like high poly count or large instances. My plan was to use this new geometry system to have smooth roads without high poly count from regular Parts and Wedges.
[KnY4TGp|690x433]
I also tried splitting the road segments into separate pieces as they’d be in Roblox as parts (190 meshes total). This worked… sort of. It ended up causing obnoxious bumps along the road- too noticeable for me to not care about.
Using the “Default” fidelity setting works for flat and simple roads however, to achieve the complex shapes, bends, and banking, this setting doesn’t fair well.!
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This feature in its current state is a step forward to making mesh collisions useful for surfaces, but I’m still running into some pretty serious issues.
PreciseConvexDecompisition:
Original:
Running some tests with a vehicle shows that the collision box is nowhere near the roadway:
When I look at the way the collision boxes are being generated it almost reminds me of Blender’s decimate modifier with the Angle setting set super high. This feature needs some adjustment before it’s useful for generating accurate roadway surfaces.
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Yeah I noticed that this doesn’t work super well with roads. I think part of the problem is that we still normalize the data to a 1000 x 1000 x 1000 cube. So we lose quite a bit of precision on large float objects.
@AndrewSVO do you mind uploading your model? I already have @TwentyTwoPilots’ model, I want to see if I can improve by tweaking some settings internally.
4 Likes
Got it here, i’ll direct message it to you.
My studio keeps crashing whenever i try to enable this feature… It was working the day this was enabled as a beta feature but now its not anymore.
Edit: It was the default blender landscape that was crashing it. I think it was because it was just a plane without thickness, added a face and now its working.
As a 3D Modeller who sometimes struggles with Collisions, thank you.
If you wanna increase the triangle count allowance for importing parts too, I think that would make every 3D Modeller’s day.
This is an amazing feature, its going to help me a lot since in the game im making the meshparts will have doors and interiors, thanks a lot for adding this!
This feature is amazing, helps out a lot especially with cars and roads even tough there is a few bugs.
