3 ms·

I wonder how other engines compare when it comes to LODs and similar systems. Godot has automatic LOD which seems pretty cool for what it is: https://docs.godo

I wonder how other engines compare when it comes to LODs and similar systems. Godot has automatic LOD which seems pretty cool for what it is: https://docs.godotengine.org/en/stable/tutorials/3d/mesh_lod.html https://docs.godotengine.org/en/stable/tutorials/3d/mesh_lod... Unity also has an LOD system, though despite how popular the engine is, you have to create LOD models manually: https://docs.unity3d.com/Manual/LevelOfDetail.html https://docs.unity3d.com/Manual/LevelOfDetail.html (unless you dig through the asset store and find a plugin) I did see an interesting approach in a lesser known engine called NeoAxis: https://www.neoaxis.com/docs/html/NeoAxis_Levels.htm https://www.neoaxis.com/docs/html/NeoAxis_Levels.htm however that engine ran very poorly for me on my old RX580, although I haven't tried on my current A580. As far as I can tell, Unreal is really quite far ahead of the competition when it comes to putting lots of things on the screen, except the downside of this is that artists will be tempted to include higher quality assets in their games, bloating the install sizes quite far.

kllrnohj 2y ago
In theory Nanite is superior to precomputed LODs. In practice it's less clear cut as they aren't going to be as good as artist-created LODs and it's not entirely reasonable to expect them to do so. Also the performance cost is huge as Nanite/virtual geometry is a poor fit for modern GPUs. iirc peak fill rate is 1/4th or something like that as GPU rasterization works on 2x2 quads not per-pixel like shaders do.
- jsheard 2y ago
  Rasterizing very small triangles in hardware is indeed inefficient due to the 2x2 quad tax, but one of Nanites tent-pole features is a software rasterizer which sidesteps that problem entirely. IIRC they said that for a screen entirely filled with triangles roughly the size of a pixel, their software raster ends up being about 3x faster than using the dedicated raster hardware.
  - kllrnohj 2y ago
    Yes but I'm talking the other way around. Nanite is 1/4th the performance for triangles that aren't 1-3 pixels in size, which is the majority of the time. The main selling point of Nanite is really just to reduce artist costs by avoiding manual LODs. But a high quality automatic LOD at build time may (read: almost certainly does) strike a much better balance for both current and near future hardware
    - jsheard 2y ago
      Nanite batches up triangles above a certain size threshold and sends them to the hardware rasterizer instead, since it is faster to use it in those cases. This was all documented from very early on.
    - jms55 2y ago
      > But a high quality automatic LOD at build time may (read: almost certainly does) strike a much better balance for both current and near future hardware You can't have a manual LOD for a cliff where half is near the player and should be high resolution, and half is further away and can be low resolution. Nanite's hierarchical LODs are a huge improvement for this. You're also underestimating the amount of time artists have to spend making and tweaking LODs, and how big of an impact skipping that is.
      - incrudible 2y ago
        This is assuming you have this "one big cliff mesh". This is the Nanite mindset: Just let the artists throw anything that comes out of their DCC at it. That is a great value proposition for studios, especially the ones that fail the marriage of art and engineering. It's a bad value proposition for end-users. Nanite is much slower for the same image quality that a bespoke solution would offer, which is evident with several AAA titles that choose to use in-house tech over UE.
    - guitarlimeo 2y ago
      Nanite is actually good at AAA graphics for hardware stacks that don't do raytracing well, but if raytracing gets faster, Nanite becomes more useless as it doesn't work well with raytracing. What Nanite is actually good with is providing LODs for only parts of the mesh, so that might get some longer use in the industry. https://threadreaderapp.com/thread/1809936882278469878.html https://threadreaderapp.com/thread/1809936882278469878.html
elabajaba 2y ago
Intel Arc GPUs are terrible for Nanite rendering, since they lack hardware support for both indirect draws (widely used in GPU driven renderers, Intel emulates it in software which is slow) and 64bit atomics, which are required for nanite.
- cubefox 2y ago
  That's interesting. Are there benchmarks on UE5 games which back this up?

kllrnohj 2y ago

In theory Nanite is superior to precomputed LODs. In practice it's less clear cut as they aren't going to be as good as artist-created LODs and it's not entirely reasonable to expect them to do so. Also the performance cost is huge as Nanite/virtual geometry is a poor fit for modern GPUs. iirc peak fill rate is 1/4th or something like that as GPU rasterization works on 2x2 quads not per-pixel like shaders do.

jsheard 2y ago
Rasterizing very small triangles in hardware is indeed inefficient due to the 2x2 quad tax, but one of Nanites tent-pole features is a software rasterizer which sidesteps that problem entirely. IIRC they said that for a screen entirely filled with triangles roughly the size of a pixel, their software raster ends up being about 3x faster than using the dedicated raster hardware.
- kllrnohj 2y ago
  Yes but I'm talking the other way around. Nanite is 1/4th the performance for triangles that aren't 1-3 pixels in size, which is the majority of the time. The main selling point of Nanite is really just to reduce artist costs by avoiding manual LODs. But a high quality automatic LOD at build time may (read: almost certainly does) strike a much better balance for both current and near future hardware
  - jsheard 2y ago
    Nanite batches up triangles above a certain size threshold and sends them to the hardware rasterizer instead, since it is faster to use it in those cases. This was all documented from very early on.
  - jms55 2y ago
    > But a high quality automatic LOD at build time may (read: almost certainly does) strike a much better balance for both current and near future hardware You can't have a manual LOD for a cliff where half is near the player and should be high resolution, and half is further away and can be low resolution. Nanite's hierarchical LODs are a huge improvement for this. You're also underestimating the amount of time artists have to spend making and tweaking LODs, and how big of an impact skipping that is.
    - incrudible 2y ago
      This is assuming you have this "one big cliff mesh". This is the Nanite mindset: Just let the artists throw anything that comes out of their DCC at it. That is a great value proposition for studios, especially the ones that fail the marriage of art and engineering. It's a bad value proposition for end-users. Nanite is much slower for the same image quality that a bespoke solution would offer, which is evident with several AAA titles that choose to use in-house tech over UE.
  - guitarlimeo 2y ago
    Nanite is actually good at AAA graphics for hardware stacks that don't do raytracing well, but if raytracing gets faster, Nanite becomes more useless as it doesn't work well with raytracing. What Nanite is actually good with is providing LODs for only parts of the mesh, so that might get some longer use in the industry. https://threadreaderapp.com/thread/1809936882278469878.html https://threadreaderapp.com/thread/1809936882278469878.html

elabajaba 2y ago

Intel Arc GPUs are terrible for Nanite rendering, since they lack hardware support for both indirect draws (widely used in GPU driven renderers, Intel emulates it in software which is slow) and 64bit atomics, which are required for nanite.

cubefox 2y ago
That's interesting. Are there benchmarks on UE5 games which back this up?