AC2 game : Textures Atlas and Tilling

[YouGroove]

Really interesting AC2 game analysis :

 

Article :

http://www.mapcore.org/page/features/_/articles/technical-breakdown-assassins-creed-ii-r24

 

Some video :

 

Interesting: detailled tiling textures only used in near view LOD, and using atlas low res texture for other distant LOD. In the video that's awesome how much the wood texture is used everywhere.

 

Another great shader feature :

However, these textures being very tiny, the developers used vertex painting to blend details and break the repetition.

 

 

Some really great optimisation tips on how to decrease draw calls :

 

Each time you change a mesh for a new one you will create a new drawcall, because for the engine it's not the same geometry. This rule applies for the shaders too. If you change the shader, you don't render the same thing, so you have to change the way you render it. This means a new API call.

 

A common solution to this is to batch your calls. 'Batching' means to group some meshes together before calling the API to draw them. This is why it takes less time to render a big mesh than multiple small meshes. How to batch these meshes if chosen by the engine, there is no best rule for this and it depends a lot of what you want to draw. In the case of the Anvil engine, you are focused on drawing large and open spaces. The best way to improve the performance in this case is probably to batch per shader. So each geometry using the same shader will be sent together to be rendered. This way, reusing textures will allow you to batch a lot of things and gain a lot of time.

 

 

Conclusion :

 

Assassin's Creed II was a really good improvement compared to the first game, however it looks like the engine faced a lot of new constraints which were not totally well handled. The way the LODs appear and the nice but still limited quality of the lighting are good examples of that. Even on modern computers today the game gets some slow-down in certain places.

 

The engine was improved for the next game iterations and increased the amount of details and the quality of its lighting to finally show beautiful cities as we can see in Assassin's Creed III today.

 

 

Let's wait LE3 to bring LOD and later texture atlas system in the editor