Two questions about Lumen from a friend of mine who is developing an in-house app with lots of meshes procedurally generated at runtime.
- Will it be possible to build Lumen-needed data for runtime procedurally-generated meshes?
First of all, our generated meshes are guaranteed to be “modular”, and can satisfy whatever future restrictions because we have full control (which is opposite of many teams, who have difficulties), so it’s likely to be very suitable for Lumen.
However, in runtime, when building UStaticMesh from MeshDescriptions, bFastBuild must be false, so all these meshes cannot bounce light, which made Lumen almost completely useless. I understand that building Lumen-needed Data (MeshCard related data, SDF etc) is time-consuming, but since our procgen meshes are relatively simple, and it’s acceptable to stall our app during generating meshes (it’s not a game), A very rudimentary support is sufficient for our case.
It would be perfect if you can add a flag in FBuildMeshDescriptionsParams that allows to build lumen data with UStaticMesh::BuildFromMeshDescriptions in Runtime, but it’s also good enough to require us to provide some convex shapes/AABBs to approximate the mesh and build Lumen-needed Data out of the approximation shapes or even require us to compute these data ourselves and just provide some interface to import the data.
With the increasingly powerful GeometryCore and GeometryFramework available at runtime, we really want to make good use of them.
- Any chance that Lumen will work on high-end iPads?
While I know Lumen will not support general mobile renderers in near future, is it possible to use lumen (software raytracing) with high-end (A15/M1/M2) iPads?
Last time, we added manually added “bSupportsLumenGI=true” to IOS/DataDrivenPlatformInfo.ini’s “ShaderPlatform METAL_MRT” section but it crashed.
Since our app is an in-house app, we have full control of which iPads and OS we use. I wonder whether this is “theoretically possible but no one tried and will not be officially supported” or “there are known problems not easily resolvable”.
We don’t use Nanite (it doesn’t support runtime procgen meshes anyway) or VSM and can sacrifice some lighting features that requires HWRT or other capabilities that iOS doesn’t have, as long as the GI is (roughly) matching DX12 for the same scene.
In general, we’d be happy to know your opinions about supporting more graphics features on high-end iPads. Game industry may not need this much, but for ArchViz and product design we usually use iPads whenever possible.
Thanks!