Unreal Development Kit engine

Lights and shadows. The performance killers.

The last week, we placed the last items for the hospital scene. We need to place some interactive elements yet, but the basic scene setup was already done. However, when we tested the performance in the low end machine, it was almost unplayable (less than 10 FPS). This was due to the amount of dynamic lights and real-time shadows in the scene. While we can simply turn off the shadows in a low end machine, managing the dynamic lights its a bit more complex.

The easiest way to optimize the lights of a scene is to simply switch them to static ones. But, and here comes the problem, our scene needs to be dynamically lit, so we can have flickering lights, malfunctions with the lamps, and dark rooms changing at real-time. Each dynamic light adds a lot of rendering work to the GPU, so we needed to optimize their usage.

After some heavy work with the lights, and the organization of the rooms, we have added some code to occlude the lights, and just render the dynamic lights that are visible from the user perspective. ALso, we have made some changes to the shadow casting, and the game is running three times faster than before. The actual numbers : up to 115 FPS in the high end machine, and up to 40 in the low end one. That is a very good speed for a level with more than 300 objects and thirty-something lights.

The night vision filter.

Our implementation of a night vision filter in Unity was a very complex one, which involved lights, transparencies, particle effects, brightness changes and shader switches. It was a lot of work to setup a scene which could work with standard and night vision lights, and at the same time have a good performance. However, in UDK, we went for a post-process effect approach.

This effect colorizes the scene, and at the same time manages some light saturation and vignetting effects. This makes the effect a lot more real, making the scene brighter and even managing some noise effects. It is being tweaked to make use of other camera effects, such as loss of focus, pre-warming, malfunctions, etc.

The lighting of the scenes is also being readjusted to work well with this new filter. We have to tweak it also to match the different night vision styles of different cameras, be it the classical gree
nish filter, or the black and white one from security cameras.

So far, we are very happy with the results. But this leads us to the first look at the Hotel level, to be featured in the upcoming demo :

The new level for the demo. Micro-scene number 2,

The Hotel

For this level we wanted to create a scene as close as possible to real-life places. We made a long research work, collecting as many pictures as we could  from many hotel rooms and decoration styles from all over the world.

Countless hours of analyzing the images were needed to recreate the lighting, the material properties, and make the level as real as possible. This is our first prototype for the level.

So far, it runs a little slower than the hospital due to the use of very complex features, such as real-time reflection and refraction, high quality lighting, complex translucent materials, and high quality lightmaps. It is not yet optimized.

The hotel hall has a marble like material with real-time relfections of the scenery, which requires a lot of power from the GPU.

The mirrors use a similar feature, and there are two mirrors in each room, and there are eight rooms on the scene. Using some occlusion and triggers, we are optimizing it as much as possible, but we have also made some static cubemap reflections for the lower end machines, to improve the performance.

Everything in this scene is using real-time shadows, so it is a little more heavy for the computer. But this also means that the performance gain will be higher if you turn off some of the advanced effects. We are checking also that the quality loss is kept to a minimum once you turn off all the effects, so the low end computers can run the game smoothly, but without a lot of graphical loss.

Here you have a little short video to see in action the new level, and the development progress that we have made.

Thanks for reading this article,  and we hope to see you in the next one, which will include (hopefuly) some info about the development of the characters of the game, for this new demo.

The Irreverent Software Team