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Comment by ehutch79 | Hacker News Reader

Wait. that doesn't sound like you're doing 1000s of raycasts? Just a few, maybe a dozen?

also, sounds like you're using JS, not Godot?

Well, I would like to be able to do 1000s of raycast per frame (360 for each bot), but cannot and yes, I do not use godot, but my own engine (with pixijs for graphics and a emscriptem port of box2d for physics https://github.com/Birch-san/box2d-wasm.) Godot uses box2d, too, so that would be convenient, if I switch to godot, but only if it is worth the performance improvement, which it currently does not seem to be. Maybe next year.

It's hard to evaluate this without seeing a screenshot of your game, but 360 raycasts per bot per frame for a basic 2d game is INSANE.

It sounds like you are trying to query every angle in every direction for every character. This is madness.

I have a 3d space game in Unity which uses raycasts for navigation. Each ship fires a maximum of 1 navigation raycast per frame with a sweep pattern. In addition there are anti collision thrusters placed around each ship which fire roughly every second in a staggered pattern to prevent ships from getting stuck

In my fully 3d game, that's effectively ~1 raycast per frame per enemy. To locate hostiles, each ai character scans a runtime set of potential hostiles and does a line-of-sight query roughly once every 5 seconds.

There definitely is another issue going on here with your setup that is independent of the extreme overhead in Godot.

I would recommend Sebastian Langue's excellent boids video to get a sense about other strategies to deal with these types of queries: https://www.youtube.com/watch?v=bqtqltqcQhw

It's possible that they are building a game in which players can program bots that only know the state of the world by performing raycasts, as if it were a sensor of sorts. That would be a valid reason to require such an amount of raycasts per bot - although I probably would not run them every frame, but rather spread the load throughout multiple frames.

Yes exactly. But the projectiles are moving every tick, so the evading logic wants to run every tick as well. But optimizing that will be up to the player..

I’d recommend cheating! It only has to appear to the user that the bot is scanning the world. For example in this specific case you could find all the projectiles close enough to the bot to be detected and do one raycast per projectile to determine visibility. This is functionally the same result as many dense raycasts but at a fraction of the computational cost because you have all the information already in the simulation.

Although I really like the idea of giving the player control over how the bot raycasts and letting them optimise that. Lots of fun strategies to find there! I’d even bound it so they can’t afford to do too many raycasts so they have to get creative.

> Although I really like the idea of giving the player control over how the bot raycasts and letting them optimise that. Lots of fun strategies to find there! I’d even bound it so they can’t afford to do too many raycasts so they have to get creative.

This is actually exactly what I did when I built a similar game about a decade ago! Bots had a budget of 20 raycasts per second, which would slowly replenish. It was the bot programmer's responsibility to figure out the best way to use them. It was a lot of fun! :)

"It sounds like you are trying to query every angle in every direction for every character. This is madness."

It is just a different game than yours, so maybe don't judge?

The usual solution for something like this is just to spread the work over multiple frames. Most game enemy logic doesn't need running every single frame. Update 10% of your bots every frame.

Also consider whether 360 rays is really needed to begin with, one ray per degree sounds like an arbitrary first-pass value. Can you cast a smaller set of rays first, and only cast the in-between rays if certain conditions are met (e.g. the initial rays hit something close, or their hit distances vary significantly)

"Can you cast a smaller set of rays first, and only cast the in-between rays if certain conditions are met "

Yes I can do this. But my case is really special as in basically the players have to do this by themself. As it is (also) a hacking game, meaning they have a limited scan budget and need to figure out to spend it the most useful for their bots.. but since they also want to evade projectiles and other bots, they want to scan as much as possible to not miss a threat.

So it works the way it is. Just would scale better, with better raycast performance.

I probably should have hinted more above, why my case is really special, but that was kind of my point, there are always special cases. And I do not want to limit my design, because of a bad raycast implementation.

You can still optimize this. If the scan has to establish line-of-sight between bots, your engine can establish that, and when firing raycasts, to skip those that are known to be misses. It doesn't change anything for the bot that fires raycasts. You could also calculate extremes (leftmost and rightmost) and return positives in between. This would decrease number of raycasts by two orders of magnitude. Also add a possibility to skip every 2nd, 3rd etc frame so that you can evaluate if it impacts game play.

Wait. I was thinking 1000s of objects doing raycasts.

Ideally yes, this is what I would like to do, to be able to control armies of bots. So because of the limitations, there are only 2-3 smart bots and lots of dumb ones.

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