replacing raindrop.nif doesnt change the nif ingame
im using this http://www.nexusmods.com/morrowind/mods/43656/? to replace the vanilla rain, but there was NO change ingame. tested with vanilla MW, and it works just as intended.
Because the NIF file for rain isn't an actual particle system, it's just a single rain drop. In theory, we could use that file to build a particle system from it, that just raises some other concerns like how to batch the meshes effectively which osgParticle doesn't seem to provide a nice way to do.
#10 Updated by Miloslav Číž 3 months ago
I'm inspecting the rain NIF file in Blender and it's not only a single raindrop, but a whole mesh consisting of multiple raindrops. It looks like rain in vanilla is not a particle system at all, it's just this mesh moving downwards, so we could implement it the same way to keep compatibility with mods. Bonus: I also found rainsplash.nif which is a model of splash the raindrop makes when hitting ground, but I don't think it was in the game (someone might check please?).
it's just this mesh moving downwards, so we could implement it the same way to keep compatibility with mods
IIRC, that's what we did in a much earlier release, but the mesh alone looks bad. You have to render multiple copies at least to make it look good, which brings us back to the question of efficient batching, and it's pretty hard to do that when the Nif file could (in theory) contain anything.
It's already possible to mod the rain by changing the texture, just not the geometry of it. There are also a few parameters in Morrowind.ini regarding Rain that we could trivially use but don't do so at the moment (hardcoded instead) like Rain Diameter, Number of Rain Particles etc. I am not sure how these parameters could be used if we're also going to use the rain mesh?
Btw, have you heard of NifSkope? Might be easier to use than importing to Blender.
#12 Updated by Miloslav Číž 3 months ago
I'm not sure I understand what you mean by batching. Is it a problem to make a few instances of the mesh around the camera? But yeah, we'd be getting back to wrapping-around, which we wouldn't be able to do per-particle now, etc.
Maybe we could have both and have a setting to switch between "vanilla rain" and "openmw rain"? Because being able to mod the texture isn't enough as apparent from the mod linked in the issue description.