Is SFM CPU or GPU oriented?

[Enfyny]

If i want best perfomance, without any lags, with fast animations, good FPS and without crashes, i have to upgrade my GPU or CPU? Or may be RAM? What SFM prefer the most, in terms of pc specs?

[Capt Fuzzy]

SFM is kinda outdated, so to be honest, having a beefy CPU and GPU won't hurt, but won't make a massive difference either.
As far as RAM goes, for games and other 64 bit programs, you can never have too much RAM, but as far as SFM goes, it's a 32 bit program and as such will only use a max of about 3.5 GB of RAM, regardless of how much you have installed.

[Zappy]

Make sure to have at least 6 gigabytes of RAM, preferably 8 or more. (Source FilmMaker can only use up to about 3.5-4 gigabytes of RAM due to being 32-bit, as Capt Fuzzy says, but Windows itself and various other background programs also take up some RAM, so having more than 4 gigabytes is a very good idea.)

If you have any decent GPU, Source FilmMaker is (almost definitely) to be limited by the CPU. Sure, getting a better GPU will make Source FilmMaker render graphics a tiny bit faster, but the majority of the time spent rendering will have Source FilmMaker calculating what to render and such, which it does using the CPU. From what I know, Source FilmMaker only uses 1 CPU core, so for example, having 16 decent CPU cores is not as good as having 4 very good CPU cores. I may be wrong about this stuff, though, but I know Source FilmMaker benefits more from a better CPU than a better GPU.

TL;DR: CPU.

[Marco Skoll]

To elaborate on what Zappy says, it does depend somewhat on the scene, but usually the biggest demand on processing time for a scene is computing shadows for the lighting.

SFM's shadow mapping essentially requires the computer to calculate everything that each light can see in order to know where the light from it is shining - a process that relies on the CPU, and which can naturally get pretty demanding if a scene is using multiple lights.
(Which is the reason that the Source engine usually doesn't allow the use of more than one shadowed lights. SFM is a big exception by allowing 8).

However, once that calculation of what to render is done, Source is just using fairly basic DirectX 9 shaders, which any modern GPU can churn through like lightning.

As that the time per frame is therefore mostly dictated by CPU processing, not GPU processing, changing the speed of the graphics card usually has very little impact on the overall render time.
When I upgraded my graphics card from an HD 7570 to a GTX 750 Ti (roughly twice as powerful), it made barely any improvement to my render times on intense scenes.

Upgrading my CPU from a Core 2 Quad Q9650 to an i7 4790 though... that cut my render times in half.

The caveat is what Zappy says - that SFM doesn't support multiple CPU cores properly*, so the best CPUs are those with maximum performance per core.

* I seem to see slightly better performance when letting SFM use two CPU threads rather than one, so it's possible that it has partial support for a second thread. However, whether or not it does, it's moot when it comes to choosing a CPU; all modern desktop CPUs have at least two cores, so it makes no difference.

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But yeah, to boil it down - get a good CPU, one that prioritises per-core performance over the number of cores.