Godot Octahedral Impostors

Simple implementation of octahedral impostors in Godot. Inspired by shaderbits article and this Unity implementation. This implementation uses only one plane to imitate a three-dimensional object from multiple angles.

Installation

Clone git repository:

git clone -b v2.0-new-baker --single-branch https://github.com/wojtekpil/Godot-Octahedral-Impostors.git

Or just download a source code zip file and copy addons/octahedral_impostors to your own project. Go to Project -> Project Settings... -> Plugins and enable "Octahedral Impostors"

Overview

Features:

• Full & Hemi Sphere mode impostors
• Depth based frame blending
• Paraller baking alghorithm
• Shadow mesh baking
• Dynamic lightning support
• Builtin Light & Standandard (ORM) profiles
• Custom image atlas resolution and frames number
• Image atlas dimmensions size optimalisation for selected maps
• Alpha Cut (Scizzors) or Dither
• Atlas Covarage ratio (WIP)
• Extensible profiles and map baking algorithms
• Atlas texture post dilatation

• Batch impostor baker:

  • Automatic scene baking & basic LOD using OctaImpostor Node
  • Selective baking
  • Settings per OctaImpostor node ovewrittable in baker window

• VisualShader Nodes:

  • Create custom shaders using octahedral impostor nodes
  • Additional Atlas Texture Sampling Node

Texture Baker

The user interface is integrated with the editor. Just select any GeometryInstance (MeshInstance, ImmediateGeometry, etc..) and a button called Octahedral Impostor will show up. Selecting a node tree with a GeometryInstance will also work. CSG nodes aren't supported and would have to be converted. You can also use new batch baking mode described below.

Bake an asset to impostor

1. Once you're in the baking window, you will have access to the following controls.

   • Atlas Coverage - How much of each atlas tile the geometry will take up. Useful for if you want to add some margin to the tiles.
   • Grid size - A root value of number of images taken from different angles of baked model. 16 is recommended value
   • Atlas resolution - Resolution of atlas images created during baking. Its recommended to use 2048 in most cases.
   • Full sphere - Full sphere allows to use full octahedral sphere for baking. Only useful when the object is visible from below. For standard foliage a hemisphere should be better, because it increase resolution from the side views.
   • Profile - Select baking profile. In case of Standard baker will generate additional textures. Use Light for better performance.
   • Optimize Size - Some types of textures can be used with lower resolution. This settings decrease VRAM usage at cost of some quality loss.
   • Export with shadow mesh - By default bilboards in Godot suffers from self shadowing problem. This setting generates additional offseted mesh used only for shadows.

2. Click Generate and select where you want to save the impostor and its images; preferably inside their own folder. Wait until the progress bar gets to 100%. It should automatically (re)import the generated textures:

   • result_albedo.png
   • result_depth.png
   • result_normal.png
   • (result_orm.png)
   • Any other custom baked map

   Tips:

   • It's recommended to manually check the generated textures for bleeding and other artifacts.
   • Make sure that your 3D editor is running smoothly before baking. The slower the graphics processing, the longer the baking time.

Shader parameters:

• Albedo, Specular, Roughness, Metallic - standard PBR material parameters, it should be setup similar to baked model
• Imposter Frames - X and Y value should be setup to the same value as in "Grid size" parameter in baking process.
• Position Offset - Offsets image texture from origin. Useful when using with for example, MultimeshInstances
• Is Full Sphere - Should be setup to the same value as in "Use full sphere " parameter in baking process
• Alpha Clamp - Minimum alpha value to show. Usufull for a better frames blending
• Dither - Use dithering instead of cuting off alpha channel
• Scale - Scale of impostor
• Depth Scale - Depth texture parallax influence
• Normalmap Depth - Sometimes baked normals are too rough. You can change the influence of light on the impostor here.
• AABB Max - bounding box based impostor offset. Can be increased to fix order and shadow problems.

In a generated shader, sometimes the parameters should be changed to achieve better results.

Baking Profiles

Its new type of resource storing a list of atlas maps to be baked together with desired impostor shader & shadow impostor shader. User can create custom profiles with new map baking scripts (check /plugins/octahedra_impostors/scripts/baking/maps) and shader (can be created using provided VisualShader nodes).

Shaders

There are currently two builtin versions of shaders:

Shader	Standard	Light
Sphere mapping	✔️	✔️
Hemisphere mapping	✔️	✔️
Grid blending	✔️	✔️
Depth maps	✔️	✔️
Shadows	✔️*	✔️*
Metallic textures	✔️	❌
Roughness textures	✔️	❌
AO textures	✔️	❌
Alpha cutoff	✔️	✔️
Alpha dither	✔️	✔️
Mipmaps	❌	❌

Custom shaders can be easly added using custom baking profiles.

Batch baking mode

1. To create scene with automatic impostors LOD system each mesh object (or a group of objects) intented to be baked must be a child of OctaImpostor node.

   Impostor can be configurable in Inpsector Property panel:

   • Baking Profile
   • Atlas Image resolution
   • Imposter Frames
   • Full & Hemi Sphere mode
   • Size atlas optimalisation
   • Shadow mesh generation
   • LOD distance switching between impostor & real gemetry mesh

   Remember to postion the OctaImpostor node on the scene, try to keep child nodes translation close to [0,0,0].

2. After all desired meshes (with OctaImpostor parents) are placed on the scene Go to Project -> Tools -> Scene Octahedral Impostor Baking. Select Settings tab and choose directory to save all of the generated impostors. Its recommended to select empty directory. You can also overwritte some per impostor settings here.

3. Go back to QueuedScenes tab. Select all OctaImpostor nodes you want to bake.

4. Click Generate and close baking window after its done.

5. You can experiment with Lod Distance settings in each of the OctaImpostor nodes for best results.