No shadows = 4x(at least) FPS?

3D
1

Hello all,
First of all thank you for this game engine, I find it generally very well made and think this is an interesting project.

However I was quite surprised when I ran the example “creature_behaviors” and saw that it ran at only 24 fps on my decent PC (using linux, dont know if that matters).
After some tinkering I tried disabling shadows from all the skeletons - and wow I got 100 fps constant (My screen is 100hz so that is max fps for me).

So I am wondering is it normal to get so low FPS from using shadows?
And if that is normal that shadow have such a performance impact, do you consider doing another shadow implementation that looks worse but has better performance?

Cheers

2

Hello and thanks for the good words!

Shadow volumes indeed can have a big performance impact – they mean we render everything 2x, plus additional “shadow volume” rendering to the stencil buffer plus silhouette determination on CPU.

That said, 4x is indeed surprising.

I tested on my system (also Linux, x86_64, running nVidia) and I can see I even have less than you said, 18-20 FPS. Shadow volumes are clearly at fault, without them I have 60 FPS, which is my monitor’s refresh rate. So for me it’s not “4x difference”, but that’s just because my monitor has lower refresh rate than yours.

Actions:

  1. I optimized shadow volumes recently already, I can optimize them more :slight_smile: I’ll see where is a bottleneck and can we deal with it. There are a number of ideas (e.g. cache silhouettes, in case their calculation is expensive – while all creatures animate in this example, their shadows don’t need to animate with max fps). It’s good that I have a testcase where I can profile and investigate.

  2. We indeed have another shadows algorithm in the working – shadow maps. They are already available, kind of, but with some issues mentioned in that roadmap section. We want to work on it and remove these issues :slight_smile: Shadow maps will have a completely different performance, likely beneficial in many cases.

So, stay tuned – both AD 1 and AD 2 shall happen sometime soon (in Q1-Q2 of 2025) and we will be better :slight_smile:

1 Like