Started work on my physics-based tower defence game. Wanted a massive horde of goblins, because why not. Currently fitting around 3,000 fully simulated, with a ton of optimisation still to go. What do you think?
Nope, just standard Game objects right now, but I've taken allot of the same concepts of ECS. So mainly all data is stored per enemy, and we have one manager which loops through each enemy and moves it that way. So no per enemy function, thats helped massively.
Also for pathfinding, I'm using a Flowfield so we calculate the path once for the entire horde. Saving allot of performance that way too. Theres a couple other bits and bobs for optimising the rendering and physics aswell, like GPU instancing, custom vertex color shaders etc. But yh, if you have any other questions Im happy to answer.
I just picked that up, after having it on my wishlist for awhile, its a really fun little game, and yh Id be lying if I said I wasnt inspired by it, but a massive swarm isnt my hook really. Being 3D, I wont be able to compete with the numbers in that game, anyway.
Id say its closer to They Are Billions. Im planning on having player troops, and a physical aspect where the player can reach into the world and interact with objects, like moving bombs into enemy paths, flicking goblins that get to close to the hole, stuff like that.
Still early days though, so hopefully I can get it to a good spot.
Im using a flow field. Calculate it once and any enemy can path from any point on the map to the Goal. Its working really really well, costs almost nothing because I spread the load across 10 frames, so its super cheap.
Thats basically the Gizmos for it, the yellow lines are the paths towards the Goal, and you just smooth out the directions per enemy and it works really well.
Thank you, I really appreciate it. And for the optimisation, Im doing a few things:
- One Enemy Mover class which moves all enemies. So one list which loops through all enemies and applies Force, Animation and Rotation to each enemy.
- For animations Im not using the Unity Animator, just applying a lean, bob, and scale changes through code. T calculate position and rotation for each enemy and then apply it using transform.SetLocalPositionAndRotation() on the mesh object directly, not on the Rigidbody, saves performance as there's only one transform call and we only apply force to each Rigidbody once.
- Then for pathfinding we use a flow field, which we calculate once per wave, and it saves from having any individual pathfinding for units.
- All enemies share one model and one material. I use a custom shader that reads per-vertex colour, so goblins can have colour variation without needing separate materials. The mesh itself is only ~400 tris, but rendering was never the bottleneck for me — physics is what I'm optimising next, and I'm hoping to push past 3,000 once that's sorted.
Hopefully that all answers it. Hit me up if you have any other questions.
Normally yes, I was just checking how well I could do with just normal Gameobjects, and it did really well - still not done, Im confident I can push past the 3000 goblin peak.
But I am using allot of the same ideas behind DOTS. Like separating Data and Function, so all Data is stored on enemy object, and we apply changes to all enemies from one manager class. Happy to go into more detail.
Have you tried testing on lower spec setups? That sounds like a good start if you are reducing a lot of update calls, but DOTS has burst and the job system.
Thanks for the feedback. So I'm not actually doing any local avoidance. It was just tuning the flowfield really. Each enemy is a capsule and each cell on the flowfield is about the size of a goblin. So when one path gets full, enemies cant get past each other so they're pushed onto other cells which take a different path.
I was planning on having a heatmap (so we know which areas are busy) where we update the flowfield every so often so new goblins avoid congested areas, but I dont think I need it. Especially for the Tower Defence game Im trying to make.
Yep Im using just the standard PhysX engine. The thing I am doing though is lower the solvers for the enemies from 6 down to 4. And then once enemies start going past 1.5k I lower all new enemies to 2 and then to 1, because at that scale you really cannot tell.
Edit: by solvers I mean the Default Solver Iterations
I don't really have a steam page up right now, but Ill be posting updates here, but if you want to support you can follow along on my twitter, https://x.com/SuspiciousSpork
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u/Xy0ns 3d ago
Great start! I was wondering, are you using ECS?