Section 2: Limitations of rdLODtools
First and foremost, Billboards are 2D planes projected into the 3D world. Even with Normal-Maps they don’t have the 3D depth to give all the lighting, shadows, reflections and camera effects such as Fresnel nodes a 3D object can.
If you were thinking they may speed up your VR game, I’m sorry to inform you that they will probably not work in stereoscopic (I don’t have any goggles so can’t test)
However…
Because these Billboard LODs are displayed at a good distance, and with some tricks to help give them the appearance of depth you can get some very nice results – and at the end of the day, the person playing your game will be so busy trying not to die that they will probably not notice the occasional visual ‘pop’ as a LOD goes into a billboard – it’s quite likely happened on your screen hundreds of thousands of times when you play games.
Ocular Effects: Things such as Fresnel Effects are great, but they don’t work on a 2D plane. The good news is that at the distance your Billboard LOD will be displayed – there is a very good chance that these effects will be returning a 0.0 (or a 1.0) and you can simply force a 0.0 (or 1.0) into a blueprint to fix it (more on that in Chapter 2 Section 2).
Emissive Colors: Currently Emissive colors are only stored as Diffuse, a future update will cater to this though. It is possible with the help of a paint program to edit the created maps and make an emmisive one – again more in Chapter 2 Section 2.
Top-Down Nastiness: The biggest drawback to Billboard LODs is when they are viewed from the top-down – they pretty much just turn into a thin line making a very noticeable visual disturbance. Version 1.3 of rdLODtools which is in progress now caters to this with top planes that fade in when the LOD is viewed from above a certain angle.
You can also minimize this look in the current version by “tilting” the mesh, rather than display straight up and down, it tilts back by anything up to 45° – when viewed from above you see less of a line and more of the billboard.
Version 1.3 will have a new system in place that allows dual axis billboards which point to face the camera at any height – these Billboards do need large maps to hold the frame data (eg 2048×2048).
