3 ms·

If you’re doing thousands of raycasts per frame in any game, 2D or 3D, then something has gone wrong. Raycasts are very general, and there is often a more speci

by db48x 3y ago

If you’re doing thousands of raycasts per frame in any game, 2D or 3D, then something has gone wrong. Raycasts are very general, and there is often a more specialized way to get the same information that won’t require as much work.

moffkalast 3y ago
Maybe there's thousands of guns being fired.
- db48x 3y ago
  Ok, if you’ve got thousands of players in the game then you’re doing _something_ right, even if the raycasts aren’t helping :)
pelasaco 3y ago
I don't think how it can be wrong. I wrote a beaten-up game, 2.5D. Player(s) + Enemies + NPCs + Weapons + Bullets.. I can imagine that in some moments, we were easily doing a few hundreds of raycasts per frame.
- db48x 3y ago
  Raycasts are a very useful tool, and you shouldn’t avoid using them if they’re the only thing that will work. But a _fully general_ raycast is always the most expensive option. For example, an axis–aligned raycast will always be cheaper and might do the job just as well. The previously mentioned case of doing hundreds of raycasts all starting in the same location but each in a different direction could be done with rasterization instead. That’ll involve a single loop over all the triangles in the world instead of one loop over the same triangles for each raycast. And for NPC vision you could rasterize billboards instead of the full character geometry. You can probably simplify the world geometry too. That’s all I mean.
  - Rapzid 3y ago
    I mean it's game dev, there's always work arounds and efficiency hacks. But what does any of this has to do with improving the ABI?
    - db48x 3y ago
      The original complaint was that Godot’s C# bindings have a raycast method that returns a dictionary. The reply article point out that this is a legacy of an earlier, less performant, C# implementation and that the work to clean it up was already under way. My point is only that raycasts are already something that you want to avoid; the extra work of allocating a dictionary each time you call it is unfortunate but not fatal.
bluescrn 3y ago
I learned to code in the 8-bit days where you'd count to 1000 in a BASIC for loop to create a significant delay. I guess I've not got out of the mindset that doing anything 1000x is quite a lot (particularly when you're aiming to do it 60 or more times per second). But as somebody working in Unity (and often on mobile), there's still many cases where 1000 of something is a lot, and should perhaps be cause to rethink your approach. For example 1000 draw calls, 1000 UI elements, 1000 instances of even the most simple prefab. 1000 raycasts per frame is also something that I'd try to avoid. But if they seemed important, you've just got to try it and profile it. Nobody can answer 'what is the cost of 1000 raycasts?' without a fair bit more information.
- db48x 3y ago
  I agree that profiling is the ultimate arbiter.

by db48x 3y ago

moffkalast 3y ago

Maybe there's thousands of guns being fired.

db48x 3y ago
Ok, if you’ve got thousands of players in the game then you’re doing _something_ right, even if the raycasts aren’t helping :)

pelasaco 3y ago

I don't think how it can be wrong. I wrote a beaten-up game, 2.5D. Player(s) + Enemies + NPCs + Weapons + Bullets.. I can imagine that in some moments, we were easily doing a few hundreds of raycasts per frame.

db48x 3y ago
Raycasts are a very useful tool, and you shouldn’t avoid using them if they’re the only thing that will work. But a _fully general_ raycast is always the most expensive option. For example, an axis–aligned raycast will always be cheaper and might do the job just as well. The previously mentioned case of doing hundreds of raycasts all starting in the same location but each in a different direction could be done with rasterization instead. That’ll involve a single loop over all the triangles in the world instead of one loop over the same triangles for each raycast. And for NPC vision you could rasterize billboards instead of the full character geometry. You can probably simplify the world geometry too. That’s all I mean.
- Rapzid 3y ago
  I mean it's game dev, there's always work arounds and efficiency hacks. But what does any of this has to do with improving the ABI?
  - db48x 3y ago
    The original complaint was that Godot’s C# bindings have a raycast method that returns a dictionary. The reply article point out that this is a legacy of an earlier, less performant, C# implementation and that the work to clean it up was already under way. My point is only that raycasts are already something that you want to avoid; the extra work of allocating a dictionary each time you call it is unfortunate but not fatal.

bluescrn 3y ago

I learned to code in the 8-bit days where you'd count to 1000 in a BASIC for loop to create a significant delay. I guess I've not got out of the mindset that doing anything 1000x is quite a lot (particularly when you're aiming to do it 60 or more times per second). But as somebody working in Unity (and often on mobile), there's still many cases where 1000 of something is a lot, and should perhaps be cause to rethink your approach. For example 1000 draw calls, 1000 UI elements, 1000 instances of even the most simple prefab. 1000 raycasts per frame is also something that I'd try to avoid. But if they seemed important, you've just got to try it and profile it. Nobody can answer 'what is the cost of 1000 raycasts?' without a fair bit more information.

db48x 3y ago
I agree that profiling is the ultimate arbiter.