Do instances affect/'apply' less faces or affect performance in Game engines?

[greekgooner]

My project that I am building in Maya is a small Garden. That Garden is going into the Unity Game Engine, which will be used for the Samsung Gear VR. As my garden, that already has lots of polygons, needs to be populated more, my teacher mentioned something about instances. She said how I could duplicate/create an instance of an original flower/plant and have many instances of it. She also mentioned something about it creating less polygons, or how the instances would not 'count' as being rendered in the game engine. (But I still need to see if instances work in Unity).

Now, I have read and understood what instances are mostly. You can move a face of the original mesh, and the instance of that mesh will also move. But what I do not understand is in the description of instances. "For example, you could create armies and forests full of duplicate objects without needing the memory or computing power to handle that much actual geometry".

So if I have 7 original meshes (that consist of 4 plants, 1 bush, and 2 trees), and I then create many instances of those original meshes, will the instance objects 'count' as a mesh in the game engine? What makes the object not need any memory to handle the geometry? Is the instance geometry not there?

Hopefully I have made sense here, as I mention Game Engine on a 3D Modelling programme forum 😕

Thank you!

[sean.heasley]

Hi @greekgooner great question! So the reason instancing can save so much memory when it comes to games is because the engine doesn't have to keep constantly looking for and pulling a mesh or texture. For example I'm not sure if Unity has it but I know Unreal Engine 4 has material instancing for textures. This is an incredibly valuable and important process because lets say you want to make 3 slightly different brick/wood/stone etc materials. Instead of having to make 3 different textures you can make one and then use the instancing tools to tweak the diffuse, roughness, metallic etc to get a different material. Now when the engine goes to read the material it will already have all the base textures from the original so it wont have to do any pulling for a brand new set of textures. I haven't worked too much with instancing for models but the general idea should be the same so I hope this kind of bare bones explanation helps :).