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What is Default RHI? Should I set it to DirectX12 or Default?

Development Discussion Content Creation
#1

Hey guys, what exactly is Default RHI in project settings? I have scoured the internet for this answer but didn’t find it. I understand what RHI stands for but how does it determine the output render quality especially with raytracing? UE4 documentation has a page on RHI but its just coding commands, nothing to explain what it does and how it would “visually” change your project if you select the default options.

The reason I ask is because I want to use a tool (Animated GIF Importer from the marketplace) which will crash UE4 if the default RHI is set to DirectX 12 (DirectX 12 I am assuming makes things look prettier). However if I set the default RHI to Default, the tool works flawlessly. I don’t mind this but just don’t know what I am losing by setting it to Default instead of DirectX12 ? Visually it looks like some raytracing disappears if I do that and some shadows become steppy and low res looking.
Can provide comparison images if you guys want.
Thanks!!

#2

That’s an excellent question. I’m interested in knowing it too, and it’s more of a necessity of knowing what it is and how Default is different from DX12. What I know so far is DirectX 12 contains the ‘full support’ for ray tracing, but default doesn’t. Default could simply be DirectX 11. I don’t retain 100% confirmation that it is, though. It’s easy to guess that one or the other could be a part of causing artefacts / noise / render issues when set.

#3

if you mouse over your projects name in the top right of the editor, you can see what RHI it’s using. in order to test what RHI the “default” option uses, just set it to default and check :slight_smile: here’s a hint: it’s DX11

#4

Glad someone else is also looking for these answers!
I see so basically DirectX 12 started supporting raytracing in UE and DirectX 11 simply doesn’t. Since the loss of visuals is massive for me, I guess I will have to revert back to DirectX 12 and find some other tool for my needs, as I mentioned the Animated GIF Importer on the marketplace just crashes UE straight up, if my default RHI is set to DirectX12.