It is very important that your map runs well on every machine capable of handeling the base game. If your map isn't optimized properly, this might not be the case. You'll run the chance of others having a less exiting and emersive experience, then you wanted to evoke with your map. "I don't care if everyone has a great experience playing my map!" said no decent modder ever. At least think of the negative ratings and comments you could possibly risk by not optimizing your map. I've played some community maps that ran considerably worse (20fps) compared to the base game(50fps). It made me not finish those particular maps simply because they were downright unplayable to me. It is very good practice to always uncheck all the collision flags on a decal. Why? Nothing has to collide with a decal, ever; so you shouldn't ask your computer to be calculating collisions for it -right? Also check the 'NavMesh transparent' Flag while your at it. Applying these same settings to very small objects should also give your map a slight increase in performance. These settings have been applied to most of the objects in this example image like the documents, food and toilet-paper as well as the decals:
Objects that aren't ever going to be visible to the player, should be deleted. You should be aware of this one. Less objects=better performance; so try to delete as many unnecessary objects as possible! It is commonly forgotten, but this includes grounds underneath houses and buildings that have been joined together. You should avoid very large open areas at all times! The game only visually renders objects/AI visible to the player at any given time; hence your framerate goes up when you look directly up or down. (Your not looking at many objects this way) So you can imagine what could happen on certain machines when the player enters an open area; lag spikes.
Want to create a large horde of zombies? Use a crowd spawner.
Not only is it way more convenient to use a crowd spawner instead of a regular spawner to create a large group of scattered zombies, it is also the best way performance wise. The engine has to parse way more calculations for your individual zombies as opossed to when they are placed in a crowd; thus giving them all the exact same atributes/handled the same way.
Optimisation gets more difficult the Higher your own PC specs are. Just because you are able to run a certain environment at 60 fps without issues doesn't mean that everyone can! Try to test your map on multiple computers if possible; Maybe your friends could help out with this? Beta Testers?
I hope you found this guide usefull! Good luck optimizing your maps! Note: I will continue to add to this guide when I have more to share. Feel free to share your own tips on optimisation. Special Thanks: - Rabid Squirrel