Impostors - Runtime Optimization

Next generation of Imposter System asset with DOTS in mind.

When creating big worlds it's important to show users large-scale scenes with lots of objects in the background. That's a tough task that requires optimizing shaders, materials, meshes, and so on.

With the help of Impostors, you can greatly simplify this task!

Impostor - fake object(quad), that tries to look like its original object. It's very cheap to render but with a trade-off between performance and visual quality.

We don't really need high visual quality at distance, because distant objects take tiny space on the screen. That's why there are techniques like LODs (Level Of Detail).

Impostors expand this approach, and in some cases can completely replace it.

Why impostors?

There are several problems with LODs

it requires manually creating additional assets for each object - meshes with fewer polygons and materials,
these additional assets increase build size,
there might be a noticeable difference between LODs, which pop in and out when player moves.

Poping problem is really hard to solve because it's just the trade-off between performance and visual quality. But with Impostors we can solve the first two issues:

impostors don't require manually creating additional assets,
impostors don't increase build size,
impostors work with stylized custom shading,
in perfect scenarios impostors look exactly like the original objects.

How impostors work

The concept of impostors is quite simple. We just take a photo of the object from a specific angle, and then show this photo as a sprite instead of the original object. Sprites are super cheap to render: they use special shader without lightning calculation and require only 2 triangles to draw. Whenever camera changes position we need to regenerate the photo to represent object from a new angle.

Important note

Again, we stuck with the trade-off between performance and visual quality.

Impostors are not a panacea and cannot replace standard rendering.

But it provides the opportunity to fill your scene with lots of distant details if your project fits several conditions.

When to use impostors

Before we continue with this chapter I want to mention: if you have any doubts or questions about impostors working with your project, feel free to contact me with some gameplay footage or at least a high-level overview of what is going on in your game. I will try my best to answer your questions and let you know whether Impostors fits your project.

Last note, Asset Store provides refunds, and I have never rejected refund requests, so you are covered.

1. Camera rarely changes position

The best scenario for impostors!

Regenerating impostor's image is a rendering operation, which we are trying to avoid as much as possible. When camera doesn't move we don't need to update anything.

Genres: VR with teleportation movement or steady gameplay, visual novels, side-scrollers.

2. First-person character camera

Works perfectly with impostors!

Genres: open-world FPS, battle-royal, survivals.

3. Flying or top-down camera

Such camera behavior requires constantly regenerating photos of impostors, which leads to way less performance boost. However, I can't say that impostors cannot be used in such games! Example scene shows exactly that scenario.

4. Fast-paced camera movement

The weak part of impostors.

Games like racing and flying simulators might not work with impostors as good as others. It depends on what you are trying to achieve. Feel free to contact me and we will try to understand whether your project works with impostors or not.

5. Games with procedural objects

If your game has procedurally generated meshes, I doubt you have LODs for them:)

In such a situation Impostors package comes handy because it generates everything at runtime!

6. Low-poly games

It depends on the platform you targeting and the count of objects you want to present in your scene. Generally speaking, impostors are overkill for games with a low poly count.

Limitations

- Requires shaders that support forward rendering and RGBA ColorMask.

- Whenever lighting condition changes impostors' images need to be updated.

- At a close distance it's quite easy to distinguish impostor from the original object, so they must be used at most at 10% of camera screen size.

- For now, Impostors doesn't support semi-transparent objects. Only Opaque and AlphaTest/Cutout shaders.

- For now, Impostors supports only one directional light plus ambient light.

Features:

Significant decrease in poly and drawcall counts
Works with stylized custom shading
No asset pre-processing, no baking
No additional assets
Doesn't increase build size
Generates everything at runtime
Fast setup
Multiple cameras
VR (tested with Oculus Quest)
Utilizes max performance using Jobs and Burst
Supports moving objects

Dependencies:

Unity 2020.3.16 - 6000.2.x
Burst
Mathematics
Collections

Supported Render Pipelines:

Built-in
Universal
It may be used in custom RP (requires a bit of coding to embed impostors into RP)
NO OFFICIAL SUPPORT FOR HDRP

Supported platforms:

Every platform that supports render textures, which is almost every platform supported by Unity.

WebGL is an exception because it doesn't work with the multithreading Jobs System.

Links:

Documentation

Forum

Release Notes

v2.1.0 - 29 Nov 2025

Fixed URP 17 RenderGraph errors and warnings (removed scheduled update mode).
Fixed warnings for the Unity 6+ about changed API.

v2.0.1 - 27 Jul 2023

Added DemoDisplay with quick access settings in sample scenes.
Fixed impostors-dither-pattern texture format which caused crashes on old mobile devices.
Fixed integration with new InputSystem in samples.

v2.0.0 - 25 Jun 2023

Major version change. Upgrade from v1 guide.

Bumped min supported Unity version to 2020.3.16f1.

Added support for Unity 2023.1 URP.
Improved how URP proxy works. No more confusing and tedious setup.
Added support for URP asset render scale.
Added support for resolution scaling.
Improved imposters shader to eliminate outline issues.
Improved light calculation for both BiRP and URP.
Added RenderType = ImpostorsCutout to shader to support shader replacement.
Optimized impostor shader vertex stage by removing waste vector normalization.
Refactored shader structure to simplify custom modifications/extensions.
Changed fading effect to be affected by timeScale.
Updated dither texture to proper blue noise pattern.
Improved menu item commands to work properly with Undo system.
Impostor shader no more shows in the select shader menu.
Added sample shader that supports both BiRP and URP.
Added new cyan debug color for 32x32 imposter.
New sample camera controller.
Added button to auto setup RP proxy.
Changed some APIs to have more meaningful and consistent naming.
Fixed long bothering issue on some hardware. Mainly on Mac and iOS devices.
Fixed fog in URP to be consistent with rest shaders.
Fixed bug in build with enabled Graphics Jobs.

v1.0.7 - 26 May 2023

Improved usage of static fields to work better with Enter Play Mode settings.
Improved in-editor impostor rendering. Now changing object's shader won't produce cyan impostors.
Removed unused directives in scripts.
Fixed light color issues with temperature and color space.

v1.0.6 - 04 Nov 2022

Added script to convert terrain trees into scene object to use Impostors.
Added example scene that showcases Impostors for terrain trees integration.
Renamed some assets to prevent asset pollution.
Fixed missed reference to RenderPipeline.Core assembly.
Fixed a small issue with impostor texture resolution.

v1.0.5 - 29 Jun 2022

Added support for URP's deferred rendering
Added DepthNormal pass for URP
Added warning about Graphics Jobs setting
Improved warnings on ImpostorLODGroup
Fixed HDR light color
Fixed restoring camera settings after impostor rendering
Fixed issues with CrossFade effect
Other minor improvements and fixes

v1.0.4 - 15 Apr 2022

Added immediate mode impostor rendering for URP (must fix issues with VR in URP projects)
Added warning about SetPass calls count when inspecting ImpostorLODGroup
Added new ProfilerMarkers
Improved bounds calculation to support not symmetrical objects
Improved rendering of lightmapped and statically batched objects
Removed DrawMesh rendering command which caused too many troubles
Fixed issue with lightmap index unexpected value
Other minor improvements and fixes

v1.0.3 - 18 Mar 2022

Fixed bug with frequent impostors enabling and disabling

v1.0.2 - 27 Jan 2022

Fixed bug with throwing errors on scene load in some conditions

v1.0.1 - 12 Nov 2021

Fixed depth writing in forward rendering
Fixed light angle delta not affecting update importance

v1.0.0 - 07 Nov 2021

Requires clean installation.

Added support for dynamic/moving objects
Added ability to more precisely control update queue
Added instant impostor creation for objects that become visible
Added MarkGoingToDestroy method to remove waste allocations on object's destruction
Improved overall system performance
Improved sorting algorithms
Improved editor for ease of use
Fixed URP rendering on Oculus Quest

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v0.9.6 - 20 Jun 2021

Requires clean installation.