At Sundog Software, we’ve always focused on our customers more than our competition. But, we are frequently asked “how are you better than your competitors?” So, I did some research on the name that seems to come up most often – Simul’s trueSKY product (formerly Simul Weather). The truth is, our SilverLining Sky, 3D Cloud, and Weather SDK is the best choice for some customers, and Simul’s TrueSky is the best choice for others. Here’s my best shot at objectively guiding you through the differences.

trueSKY is a trademark of Simul, so let’s get that out of the way. SilverLining’s a trademark of Sundog Software. I’ve done my best to present accurate data using publicly available information on trueSKY, but feel free to contact me if I got anything wrong. All images below are from SilverLining – I didn’t want to use Simul’s images without permission.

Platform Support, and Ease of Integration

Sundog's SilverLining 3D Clouds and Dynamic Sky in a Unity project.

SilverLining and trueSKY are fundamentally different in how they approach integration with your game or simulation engine. With SilverLining, you call into its API to do the actual drawing of the clouds, sky, and weather effects. trueSKY computes volumetric data for clouds, and hands it back to the application to handle drawing it. Simul provides sample code for doing this and direct integration for some engines, of course, so it’s not as hard as it sounds – but it does require some extra effort during integration. Customers integrating into their own engines have commented to us that SilverLining’s integration was much easier.

But, this means SilverLining needs to support many platform-specific rendering API’s, including OpenGL 2-4, and DirectX 9-11, on multiple platforms. It makes integration of SilverLining extremely easy – just a few lines of code in the right place. But, this comes at the cost of platform support. SilverLining supports PC, Mac, Linux, iOS, and Android, but it does not support consoles such as Playstation and X-Box (other than through our Unity engine plugin,) nor can we support future hardware we don’t have access to. Since trueSKY just gives you data to render on your own, the onus of doing platform-specific rendering is shifted to the customer, but this opens up support for any platform.

Source code licenses are available for SilverLining, and all of its rendering code is centralized into one module – so it is possible to get SilverLining running on other platforms with extra effort. A couple of customers have done this before, and for example got it running on X-Box at one point.

So – if you are targeting PC, Mac, Linux, and/or mobile – SilverLining will offer a quicker integration, since it not only creates cloud data but also renders it for you.  If you need support for game consoles and you’re using an engine other than Unity, Simul trueSKY is probably the better choice. This explains why Simul is successful in selling to large game developers such as Ubisoft, while Sundog’s customers are more evenly spread among simulation and training companies, indie developers who are either using Unity or not targeting consoles, and MMORPG developers primarily targeting desktop platforms.

Engine Integrations

While both SilverLining and trueSKY offer C++ API’s to integrate with any engine, they offer a different suite of pre-made integrations for specific engines.

SilverLining includes integrations for OpenSceneGraph, osgEarth, Unity, Ogre, Havok Vision, as well as some older engines such as SceniX and Gamebryo.

From what I could see online, Simul offers integrations for Unity, Havok Vision, and Unreal Engine 4. They may have others if you contact them – I didn’t have the audacity to try and obtain an evaluation kit from them myself, so I’m going entirely on publicly available information online here.

OpenSceneGraph is a very popular engine with our customers, and I think this reflects SilverLining’s popularity in the training and simulation community. In gaming, we had a Unity version out before Simul did, but Simul beat us to the punch on Unreal. Again I think this is due to their larger focus on AAA gaming, while we are focused on bringing AAA-quality to simulation, and mid-tier and indie game developers. That is a conscious decision on our part.


Stratocumulus GPU ray-casted clouds in SilverLining.

Both products will give you convincing time of day effects for any time and location, and create thick layers of convincing volumetric cumulus clouds with a minimal performance overhead. This alone is more than adequate for games looking to create dramatic skies that can represent continuous time of day transitions.

SilverLining however offers a wider array of cloud rendering techniques. This means we can better support a wider range of weather conditions. Partly cloudy conditions aren’t very interesting to a game designer from a visual standpoint, but they are important to companies creating flight simulators. So, we offer a unique approach to billboard splatting for creating these sorts of scattered clouds, which offers the most detail. We also offer simple procedural stratus, cirrus, and cirrocumulus clouds to add extra detail to your dynamic skydome. For heavier volumetric clouds, we offer our stratocumulus cloud type (seen here,) which is rendered using GPU ray-casting.

Simul has focused its effort on that one technique – rendering volumetric data on the GPU, which is most appropriate for thicker cloud coverage. trueSKY’s focus on this one type of cloud means they look amazing and are highly optimized, but you’ll find that SilverLining offers more choices for specific cloud types and conditions with comparable performance.

SilverLining also manages all of the complexity associated with rendering weather in whole-Earth simulations and games, using ECEF (Earth centered Earth fixed) geocentric coordinate systems. Many of our customers need to simulate virtual environments anywhere on the planet, and so SilverLining can model Earth’s ellipsoid and even render an atmospheric limb around the Earth when viewed from space.

High-Resolution Cumulus Clouds in SilverLining 3

Simul offers a “sequencer” that allows a designer to script weather and time of day effects over time, while SilverLining expects the application developer to send it appropriate weather conditions and time of day changes (or rates of change) at runtime.

From a qualitative level, there is a certain degree of art to what we do. Comparing the two products is to some extent subjective. It is certainly a great idea to obtain evaluation kits for both products, and just see how they look and perform within your engine or application under comparable conditions.

All told, customers looking for accurate simulation of a wide variety of weather conditions will appreciate SilverLining’s feature set. Game developers looking for ease of use at design time and for more dramatic visuals should also evaluate trueSKY .

Customer Base

Simul claims around 40 customers worldwide on its website. We have hundreds. In part this is a result of our lower price point and broader market – when you consider price, we’re probably comparable companies from a financial standpoint. More customers, however, means more people have been using SilverLining in real-world applications, and we’ve worked with them to iron out bugs and optimize performance and appearance for a wide range of systems and requirements.

Both Simul and Sundog have been around for over seven years. The differences in our products are such that we’ve been able to co-exist for all that time, and both products have been in active development all that time. Our competition has driven us both to continually improve the start of the art in environment rendering, and it’s been a good thing for the industries using our products.

The types of customers we have however are different. Simul’s big customers include gaming companies such as Ubisoft, and a few big simulation customers such as Boeing, Bohemia, and FlightSafety. Sundog also claims Boeing as a customer, but we have many more large simulation customers such as Lockheed Martin, L3, EADS, Cubic, NASA, the US Navy,  the FAA, and dozens more. In gaming however, our lack of console support means our largest game customers are MMORPG developers targeting PC (such as 3000 AD and a variety of South Korean game developers), PC gaming companies such as Dovetail Games, and indie developers using Unity.


Simul asks you to contact their sales staff for pricing, and you should – odds are they can cut you some sort of deal. Sundog’s pricing is completely transparent. In fact, you can get an evaluation SDK for SilverLining and order a license online without having to talk to anyone (but we’re certainly available if you need us.)

Simul has revealed some of their pricing online recently, however. Converting to US dollars, Simul’s per-SKU license fee ranges from over $25,000 for indie developers to over $42,000 for large studios. To be fair, I’m sure those are list prices and can be negotiated to some extent.

Sundog’s SilverLining is an order of magnitude less expensive. Our prices range from $2,500 per-SKU for a binary SDK to $3,500 including source code.

Wow – I didn’t even realize that myself until now.

An outlier is pricing for Unity assets, which demand much lower price points. SilverLining for Unity is available for $100 per seat, and works on any platform. Simul has announced Unity pricing of $250 per seat, and currently only supports DirectX11 based games.


Writing this, I just can’t get over the difference in pricing when you consider the features offered by both products. If you’re a AAA game developer who needs support for current and future console platforms, Simul’s trueSKY is probably the best choice. But for everyone else – evaluate Sundog’s SilverLining as well. I think you’ll find it meets or exceeds any requirements for simulation, training, or gaming, and at a much more budget-friendly price.