Outroad Fury

Helping other project with technical issues and optimization

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Context

This project was made by the year above me, i was asked to help them with technical issues during development and optimization after the game release.

Challenge

Working on a project at the end of the production, the game isn’t running well with mid-end hardware.
There is some shadows artefacts in the rendering.

Solution

Quickly adapt to the team, debugging the shadow artefact by identifying the shadow source and the method used for the shadow calculation.

Shadow Artefact

Profiling

The player can throw weapons through the map to attack an enemy.

These weapons are skeletal meshes and just like World position offset materials, they generate dynamic virtual shadow maps around them.

This feature can unfortunately generate shadows artefacts.

Cached Page

Virtual shadow Maps are mostly cached in order to use them for the next frame and so on, this function maintain good performances.

As dynamics actors can move in runtime, they use dynamic virtual shadow maps.
These ones are calculated using the object’s rendering bounds, so if the actor bounds are too smalls the shadow goes beyond the dynamic area which does not refresh the shadow as the object moves creating those artefacts.

Bounds

In the actor settings, the bounds can be scaled in order to fix this issue however we must consider that increasing the bounds scale can add extra cost in rendering, so the smaller they are the better.

This issue is easy to resolve but it is hard to find the source.

Optimization

Details

As I arrived mostly toward the end of this project for optimization, there wasn’t any framework in order to make optimized levels.

This project contained a lot of irreversible things like meshes merging, this made the optimization not optimal as it could be.

I have started profiling to identify the bottleneck.
Drawcall and polycount where the main ones.

Polycount

The polycount is the amount of polygons that a static mesh contains.

The more polygons a mesh contains the heavier it is to render.

LOD

LOD or level of detail is an optimization method that reduce the mesh polycount by it’s screen size.

Note that if the decimation is too heavy for the mesh it can leads to popping between LOD’s transition.

DrawCalls

A drawcall is a collection information that tell the computer what mesh to draw and with which material.

So if a meshes one material, it will be one drawcall and if a meshes have two materials, it will be three.

The more Drawcalls you have in the scene the more heavier it is to process for the computer.

ISM

ISM or instanced static mesh is a component that represents multiple instances of a static mesh which all share the same collision and material properties but differents transforms.

This allow the computer to process for one Drawcall several meshes and, consequently, saving performances.

Nevertheless this component can’t make uses of LODs.

HISM

HISM or hierarchical instanced static mesh is mainly the same as ISM but can uses LODs, because of that the scale of each instances must be equal to one / neutral if not this can causes culling issues.

Selector Tool

I have made this tool to make ISM and HISM.

Using editor utility widget, I can select all identical actors from the current selected actor that allows me to use the build-in Batching tool of unreal.

Plus several filters are available like “only with the same material” or “with a scale of one”.

This tool was very useful for other purpose in other projects.

Other projects

Tech Art