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Raytracing and Tessellation Bugged in 4.26?

Hello,

I had an issue earlier this week involving Raytracing on a tessellated landscape - particularly, using both caused massive black shading errors across the landscape. After some digging around, I found the console command “r.raytracing.normalbias” that seemed to fix the issue. Although, I’m not sure if this is the proper way to solve that particular issue, and seems a little hacky considering it needs to be entered into the console each time a UE4 project is loaded. At the moment, I’m using a relatively unmodified version of the OpenLand plugin, and this fix was suggested to me via their Discord. Is this a bug or 4.26? Or is this the best way to solve this?

This is due to raytrace shadows,… (as far as I know tessellation is “not yet” fully supported with raytracing shadows and landscapes,… also with Raytrace GI)

Had the same problem… r.raytracing.normalbias is kind of a trick to get rid of the “black spots” but when you look to close you’ll notice that the detailed shadows you would expect of displaced areas are not there…

Basically what’s happening is,… the black spots are the areas where the tessellation “goes” underneath the surface you’re tessellating on… you see kind of the same effect when using raytrace GI, dimmed spots where the displacement goes underneath the surface…

Right now,… don’t use raytrace shadows (If you can afford the potential performance impacts on large landscapes when using CSM, also depending on your material complexity and target hardware)… unfortunately…

On Raytrace GI I simply fixed this by giving my displacement a controllable offset to be able to offset in up axis,… so the tessallation goes always over the surface instead of under… but this doesn’t work with the raytrace shadow (at least last time I checked …)

Used this approach here Unreal Engine 4.26 Layered Autolandscape Material Preview and Quixel Surfaces - YouTube … CSM and Raytrace GI (total overkill in this scenario, but hey ;D ) … all the tessellation has a offset that lifts the visible surface higher than the actual landscape surface is

…but If there is a solution to the shadow problem,… I’m also curious…
Cheers P