VR Assets-- Polys Versus Textures

Hey Guys and Gals,

I am working on a VR project and as I am deciding on art style and aesthetic while trying to keep in mind frame rate.

I have noticed that normal maps in VR tend to be less compelling than in on the screen. I also find that additional polys, Ie wooden planks with edges that are similar to wood grain, looks really good with mo material added.
So I was wondering if I add in more polys to describe the shapes better could I gain that back by having 512 texture files or 1k textures?

Also, some one told me opacity masks in textures kill performance, but I cant find a technical write up on it. I am looking to do some foliage.


1 Like

Hi Jordan,

you’re right about normal maps. the only thing that makes assets look better in VR is more polys, more geometry. Normal maps work kind of but ONLY if you are “far away” from the model itself. if you get near, it doesn’t work in VR.

I have also noticed that the higher the texture resolution the more blurred it gets in VR (at least on a DK2). So you have to try when the model looks best.

hope that was useful to you :slight_smile:

Geometry in UE4 appears to be basically free. You can have insane amounts of triangles and very good performance ; the real cost is in shading.

Also yes, transparency does kill performance. UE4 uses a deferred shading for the main scene rendering, which is very efficient but doesn’t support any kind of transparency ; so it has to be done after the fact in a separate, less efficient render pass.

Thanks for the responses, , What size texture maps are you using, I am using 2k atm and it looks good for me.

Gwenn, That’s good news about the polys.

What to do about foliage, so far it doesn’t seem to be a huge issue. But for example I could make grass individual blades with no transparency Lets say I would have had 3 polys with transparency–Should I instead make a 200 poly grass element with no transparency? As to what is the limit? 1 to 1000 ratio or 1 to 100 ratio.

Also, Gwenn what exactly do you mean by shading-- that materials, the light pass?

Thanks for the help!

Also Gwenn, Specifically I mean Alpha masked transparency. Not Refraction type glass materials. --Just to clarify.

Anything that has any kind of (even basic) transparency has to be handled in a completely different way in the engine. Alpha masked will be somewhat lighter than a complex glass material, but it’s still rendered in a separate pass, it still has to be sorted by depths on the screen, etc. 2k maps are fine, especially if you reuse them a lot.

As far as foliage go, there is no silver bullet : it’s expensive and hard to get right. You need transparency, and geometry, and LOD so that you have detailed objects nearby (500/1000 tris) and very light objects from afar (maybe 10?). Read a lot about it, take a look at how the samples are made, how content on the marketplace is done, etc.

2k are fine, that’s what we use most of the time, too. higher resolutions don’t really make it look better (in VR).

that said, one thing to look out for is shader complexity and number of materials. the less of both, the better the performance!
you can switch to “shader complexity view” and see what materials drag down your performance (Viewport Modes in Unreal Engine | Unreal Engine 5.3 Documentation).

1 Like

Very Cool! I like that shader complexity overview! That’s great.

Okay so I have a very large oak tree that has like 12,000 polys, but it has branches and leaves included-- I might make a sample project and load the version with the alpha mask, then compare it to the poly one. I kinda like the asthetic though that I am getting with the strictly polygonal shapes.

1 Like

Is that really the case? Would that mean that when setting up a localized scene (e.g. a house in a garden, nothing else around), I can be fairly careless with the geometry (put in a large amount of detail in the meshes of the house and the interior) and will have much more influence on the performance in VR if I focus on shading, lighting, prost-processing etc instead?

Well it depends on what you call large details, but polycounts of a few million tris are mostly fine on PC.