rdLODtools Manual version 1.4

Chapter 1: Introduction to rdLODtools.

Section 1: What does rdLODtools do?

rdLODtools is a UE plug-in that adds tools to help make working with LODs quicker and easier.

rdLODtools gives you tools for manipulating LODs, all easily and quickly available from the context menu and Static Mesh Editor toolbar.

There are also tools to create Billboard, Planar, TriSprite and Cubic LODs for appropriate static meshes, these can significantly reduce draw time, allowing huge amounts of meshes in your scenes.

The new LODs are built into the existing meshes and don’t require anything but the new materials/instances to be packaged in your project (this is done automatically, the same way existing materials are packaged or you have the option to copy an embedded master material with no dependencies). This means you do not require the plug-in to be packaged with your project. They work with all platforms.

If you’re already familiar with what Billboard LODs are, please fee free to skip this bit and continue to the next page.

(Assets not included)

A Billboard LOD is a 2 or 4 triangle Plane that always faces the camera. This plane gets a snapshot of the mesh and mimics the mesh from a distance. This can significantly reduce the number of triangles in your scene. Additionally, the Billboard LOD can contain mesh snapshots at various angles to give the impression the mesh is rotating. This also helps make the transition from mesh to billboard as seamless as possible. An extra Plane is added at right angles to the viewing Plane to give depth to the shadow when specified.

A Planar LOD is a set of planes set at angles around the centre. These LODs use more triangles but give more depth to the LOD. Shadows work well for these LODs. rdLODtools gives the ability to create from 2, 3 or 4 planes (all double sided). These LODs are more suited to trees and foliage, meshes with lots of transparency. In rdLODtools, you also have the option of creating a top plane for them which gives a good top-down look.

A Cubic LOD is a Cube mesh with each face containing a snapshot of the mesh at that angle. These Cubes can be used as-is or exported to a modelling app (such as Blender) and the faces can be sliced and moved (a nip and tuck you could say) to create any low-poly shape you want. These can be very useful as low poly LODs for meshes such as buildings and vehicles and also very useful as Distance Meshes to fill your scene. They are fast as they are low poly and only use one material (2 or 3 textures).

A TriSprite LOD is a single frame Billboard that is rendered using only one triangle. These are extremely fast as the geometry is at it’s lowest possible, the textures can be very small as it’s single frame, overdraw is at its minimum and the shader is very fast.

An Octahedral Impostor is a multi-frame, dual axis LOD using either 4 or 8 triangles. These LODs have two 4 channel textures containing the Diffuse, Normal, Signed Distance field map and Depth map. These LODs provide the best quality distance LOD, but have the largest VRAM and GPU usage.

Types of meshes to rdLOD.

When deciding on if your mesh would benefit from an rdLOD, there are a number of factors to consider:

  • Is the mesh tall and thin
  • How often is this mesh in the scene
  • Does is appear close the camera and far away
  • How many materials and textures does it have
  • How many triangles is the main LOD
  • Do the materials have translucency and/or masks
  • Do you need the LOD to rotate in the Pitch and Roll axis (Trees and foliage usually grow straight up so not usually needed anyway, turn off “Align to Normal” in the Foliage or Population tool)

If it is tall/thin and there is a large number of them and the main mesh has many materials/textures using 2-sided foliage or masked – then it’s a prime candidate.

If your mesh is high-poly but only contains a simple material – consider Nanite, or creating a Reduced Triangle LOD instead – then you’re not adding an extra material to it. Keep in mind though that if you’re targeting most hardware, you’ll need LODs for the DX11 fallback meshes)

If your mesh is seen by the camera close up and far away at the same time – remember that the original textures plus the new LODs textures will be loaded in GPU memory.