ZDoom

Is it possible to rotate an actor with DECORATE only? I am not referring to flipping the sprite, as talked about here. What I mean is to turn something like an arrow-like projectile from horizontal to vertical.

Something like this: I know I could just rotate the sprites manually and inherit the old actor with the new sprites, but I'd like to do it with code if possible. Also how would back side and front rotations work when the sprite is rotated? Doom doesn't have a bottom and top view of a sprite, so how would back and front be translated to bottom and top?

Doesn't the TEXTURES lump have this feature?

I think it can rotate, however I just ended up going with the manual approach. I just copied the straight-most angled sprite and rotated it in SLADE and renamed it, then inherited the original projectile and changed it's Spawn state frames. That allows me to fire them like a normal projectile and will retain compatibility. It's good that you can fire projectiles down using the vpseed argument or this would be pointless.

Can't you set the roll property after enabling +rollsprite (and +rollcenter)?

It would only work for GL though.