UE4 VXAO Forest Part II

With all the earlier posts about VXAO, it’s time we put things together and render out a short movie that features this novel tech in all its glory. What better subject than (yet another!) forest? Forests are such a nice subject for exercises like this because they typically feature all the big and small objects crucial for testing whether one type of AO can cover most, if not all, essentials. For this reason I disabled Distance Field AO once again and tried to limit usage of any type of Screen Space AO to the least. The Kite Demo assets continue to prove their worth, although I added some which are mere modified versions of the excellent originals.

Note: Before watching the video, be sure to check the ‘HD’ button and select your prefered resolution.

The Scene

A small, basic landscape with grass, heather, some flowers and 2 types of trees. Tiny objects are culled at a reasonable distance to keep enough performance. Object density is great and we’re able to get a lot of detail for some shots. Even the fallen leaves are made of geometry although that might have been a tad overkill. As mentioned above, some modified objects were used, primarily to get some better density in tree canopies. I was curious what effect this would yield but the results ended up a bit too contrast-rich. If I’d do things over, I probably would use the same lighting as some of the more ‘ambient lit’ shots show.


A Direct Light with Ray Traced Distance Field Shadows and a Skylight with a HDRI cubemap. Intensity varies per shot. The Post-Processing volume is mainly used to get a good variety of VXAO settings in terms of range, strength and size per shot. Some close-ups feature a bit of HBAO+.


VXAO does not impact performance nearly as much as the object count. With so many small meshes and textures with transparency there’s bound to be a ton of overdraw and this eats away our framerate. We average around 20-25 fps. I did do some optimization tests and found that, by cutting out half the small nitty-gritty, framerate stabilized at 40 fps.


I rendered about a dozen individual clips with an average length of 10-12 seconds at 60fps and 200% Temporal AA as .jpg sequences. Rendering a single clip took about 3-5 minutes. The clips were then blended together in After-Effects. No other post-processing was applied, neither to the movie nor images.


Speedtree wind is somewhat of a struggle to get right. It seems there’s a ‘warmup’ stage and, to make things worse, the wind effect you see in the editor is nothing like the effect which ends up in your renders. This makes setting up wind a full trial and error experience and the results are a bit lackluster.



Closing thoughts

I had a really good time experimenting with VXAO. It’s a pleasure to use and, although I still struggle with a lot of things in Unreal Engine 4, I’ll continue to find new ways to use it where it will improve my scenes. Even after testing a number of possibilities, it continues to surprise me, both in quality and stability.

I Hope you found this series of posts on NVIDIA VXAO entertaining and maybe even somewhat educational. Please feel free to comment with feedback and questions below.


  1. Mork 22/11/2017 at 12:57 - Reply

    Wonderful tests here! I’m practicing with UE4 VXGI too, and i would like to add volumetric lights.
    I’m using a build 4.17.2 with gameware (included VXGI, nvidia vol lights etc)
    Are the volumetric lights included from 4.16 the same as NVIDIA ones?
    I suppose you need exponentialheight or atmospheric fog to make them works…
    What are you using in your tests? The included vol lights or the nvidia ones?
    thanks and keep up with the experiments, they are awesome!

    • Mork 23/11/2017 at 14:31 - Reply

      I’ve managed to make volumetric lights finally, but if i turn off Nvidia volumetric lightning i can still see the vol lights, so i suppose the engine it’s using its own tech (added on 4.16)…do you have any hints on that? Are they the same, nvidia and ue4 ones?

  2. Francisco Cruz 13/01/2017 at 18:15 - Reply

    Superb!!! Question: it is possible to have VXGI and VXAO together? Performance will be a big issue I guess.

  3. richst42Richard 02/08/2016 at 14:51 - Reply

    Hey man, looks brilliant! It would be really interesting to see some ‘before and after’ screen shots to see the extent of VXAO’s capabilities, maybe comparing that to ssao of dfao as well could be cool to see just how powerful this tech is. thanks for the awesome posts! 🙂

  4. Ben 01/06/2016 at 18:08 - Reply

    Beautiful work and insightful post. I am still trying to process that unwrapping and lightmass are not necessary to achieve something like this…and at real-time with acceptable framerates no less. Very impressive.

    • Byzantos 3D 02/06/2016 at 13:19 - Reply

      Thanks Ben! Indeed it’s sometimes surprising to see how far real-time lighting and shading has evolved. Imagine what we’ll say in another decade 🙂

  5. pilotchiao 08/05/2016 at 03:58 - Reply

    How to get VXAO unrealengine4 version?

  6. Wendell Dimaculangan 18/04/2016 at 05:03 - Reply

    This looks really good! Can you share those struggles? I want to try and see if I can include UE in mya workflow. Some say it’s not advisable if you want fast turnaround or projects with many revisions.

    • Byzantos 3D 18/04/2016 at 05:25 - Reply

      Thank you Wendell. If you’re willing to learn, anything is doable ofc. Unreal Engine is very powerful but getting beyond the basic isn’t easy. Making movies can be frustrating. The Devs are continuously improving many aspects and the (near) future looks better in that regard. My main struggle is being somewhat unorganized. That doesn’t help. UE4 keeps all assets and materials on a per-project level. I keep telling myself creating asset-collections might speed up workflow but for that to happen you just have to sit down and do it 🙂

      • Wendell Dimaculangan 18/04/2016 at 06:19 - Reply

        Thanks for the insights. I think I will struggle with UV unwrapping as I don’t do that at all :). Keep on posting I’m one of your avid lurker.

        • Byzantos 3D 18/04/2016 at 06:23 - Reply

          Will do! The UV unwrapping for lightmaps is only required if you want to use Lightmass baking. I don’t like that workflow. It produces superb results but I prefer real-time. For me it’s much quicker. Nothing I post here has been unwrapped 😉

          • Wendell Dimaculangan 18/04/2016 at 06:53 - Reply

            ok that will speed-up the workflow. And I think the lightmass baking is more on interior rendering. I mostly do exterior. But can UE handle large masterplan?

  7. Derekw 18/04/2016 at 04:15 - Reply

    Hey Aaron, looks magical! Love your work

    • Byzantos 3D 18/04/2016 at 05:19 - Reply

      Thanks Derek! How’s that Zoo-design coming? Do you get to pick a Koala if it’s done? 🙂

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