Simul Software Tech Interview: Creating Realistic Weather Effects

As we slowly reach closer to the possible release of the next generation of consoles, the graphical capabilities are going to get even higher. As always, Simul Software remains at the forefront of simulating weather effects in a game and making it look as realistic as possible. To learn more about how things have changed at the company and what their current goals are, Gamingbolt spoke to Simul Software’s founder Roderick Kennedy.

"One of our upcoming innovations for trueSKY 4.2 is geographic weather – you can have entirely different weather states in different parts of your game world – a storm rolling in from the East with clear skies in the West for example."

We interviewed you back in late 2013. It is now more than 4 years. Can you let us know what has changed at Simul in this period?

We’ve grown! We have tripled our full-time staff, and moved to larger offices here in Liverpool. Most of our business now is for engine plugins, though the standalone trueSKY SDK is still very important. But the whole industry has moved towards standard commercial engines: Unreal, Unity etc. We’ve really opened up to indie developers as well, and have started to build a great community of trueSKY enthusiasts.There’s a convergence happening where indies and triple-A’s are starting to use a lot of the same tools and techniques, and we’re excited to be a part of that process.

How has your flagship product TrueSky evolved in the last four years?

VR support changed a lot for us: you simply can’t leave any performance on the table if you want to be in VR, so that’s driven us to really stamp down on clock cycles. At the same time, we must keep evolving the feature set. In 2013, we were almost the only people doing volumetric clouds in real time. Now it’s become commonplace – many triple-A studios have had a crack at it – so we have to be the best. We used to have two types of cloud: 3D volumetric clouds for cumulus and so on, flat 2D clouds for high-altitude wispy cirrus clouds. In trueSKY 4.2 those are all done volumetrically, nothing is flat. I think our 3D cirrus clouds are the first of their kind in real time. You can have as many cloud layers as you like, all blending together, evolving over time.

Can you tell us how Simul Weather has evolved in this period?

One of our upcoming innovations for trueSKY 4.2 is geographic weather – you can have entirely different weather states in different parts of your game world – a storm rolling in from the East with clear skies in the West for example. Then the storm reaches you, the whole lighting changes.

But while we have good ideas of where we want the product to go, we try to give the customer what they want. Several studios told us they love trueSKY’s visual quality, but have no need for dynamic skies. So we’ve implemented a feature where trueSKY will generate a skybox when requested, update your lighting, then stop: the CPU and GPU cost of that per-frame is essentially zero.

Can you give us some examples, if possible, of games that have used these two technologies and the challenges you have faced?

When Bandai Namco first came to us with a request for skies in Ace Combat 7, they explained that they would want to make an emphasis on VR. We found that we had to completely change the way we draw volumetric clouds in order to look good with a headset.Because we render our clouds at a lower resolution than the screen, slight motions of the VR headset could cause aliasing artifacts. So we invented a world-space volumetric renderer that produces a stable image that looks good from any angle. The quality of what BN have achieved with it is astonishing.

"We always try to use as little as possible. It’s become almost as important as GPU time for us because every bit of memory we use is denying that space to some other part of the game."

Back when we interviewed you, the world was getting ready for next-gen consoles i.e. the PS4 and Xbox One. Now we have two new iterative consoles i.e. PS4 Pro and Xbox One X. How have you upgraded your tools for the same?

The main difference for us has been the move to 4k, and to HDR. Fortunately, trueSKY was already outputting physically accurate linear radiance values, so the information was already there waiting for an HDR display to output it. It’s been quite transparent for us.

Did you incur any additional development expenses for supporting the new iterative consoles?

Yes – not only buying the devkits, but also the expense of 4K HDR screens. And at GDC this year we’ll have at least one of those, so it makes that a more expensive process.

In our last interview we discussed about how the new consoles have 8GB of memory. Now we have an interesting position with the PS4 Pro and Xbox One X. The former has 8GB and the latter has 12GB. How do you this impacts Simul or for that matter games development in general?

We always try to use as little as possible. It’s become almost as important as GPU time for us because every bit of memory we use is denying that space to some other part of the game. We aim in a typical scenario on console to use less than 30 Mb. But that will rise to about 50 if you want very high-res clouds, as might be the case on PS4 Pro or Xbox One X.

Simul Software is GPU based tech. This raises an interesting question. The PS4 Pro has 4.2 TFLOPS GPU whereas the Xbox One X has 6. Does this mean you are able to extract more out of the X and in what ways?

Yes, it allows more work to be done in the same GPU time, so if a developer allocates 1.5ms for the sky, trueSKY can do (on Xbox One X) almost four times more work: rendering the clouds at double the resolution for example. If you want to use the extra power to go from 30fps to 60, you can still do about twice as much per frame, so resolution could go up by about 30%.

Simul Software is the face of new technology. You guys develop tech which will be used for the next 5-10 years. How do you see a potential PS5 and next Xbox changing the gaming landmark?

I anticipate a big move towards procedural content in the next generation or two. The generation of content is not limited by computing power, space or even bandwidth so much as the human capital that’s expended in creating it. I think what we’ve pioneered with skies in terms of 100% generated content, albeit with artistic input and programmed control, will become the norm for 3D objects, textures and gameplay elements. None of that takes away from the craft and creativity that goes into games, it’s a new set of tools that developers will use in ways we can’t yet imagine.

"We’re working on Switch right now, and expect to launch trueSKY for Switch within the next few weeks!"

I find it surprising that Simul is not on Nintendo Switch, specially given the hybrid system’s success. Is there a specific reason for this or is it due to its low processing power?

We’re working on Switch right now, and expect to launch trueSKY for Switch within the next few weeks!

GDC 2018 is coming up. Can you share your plans and what exciting new tech will you possibly be showing off?

At GDC 2018 (booth 1914!) we’ll have playable games featuring trueSKY running the gamut from super-cool indie projects to triple-A blockbusters. We’ll be showing trueSKY 4.2, which is a quantum leap in visual quality and power over what we’ve had before. And we have a beautiful new water system, based on the same principles as trueSKY: seamless integration, physically-based parameters, and high performance.

Is there anything else you want to tell us before we let you go?

We’ve been completely blown away by the quality of some of the indie games in the trueSKY community, and we’re super-excited to see what they come up with next.

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