During a presentation at Siggraph 2017 in Los Angeles, Gerrilla Games Principal Tech Programmer Giliam de Carpentier and Kojima Productions’ Kohei Ishiyama hosted a presentation titled Decima Engine: Advances in Lighting and AA, providing a look into the fog system that is being developed for Death Stranding.
Decima Engine has a flexible atmospheric scattering system linked with clouds and outdoor lighting, but Kojima Productions needed a system optimized for photo-realistic rendering.
Normally precomputed atmospheric scattering is one of the best methods for photo-realistic games. It works well to create a photo-realistic atmosphere, but developers often need to express artistic quantities like dense fog and colored fog in the actual game.
Instead, it would be advantageous to be able to express the photo-realistic aerial perspective (which is a technique that creates an illusion of depth by representing more distant objects as fainter and more blue) and the artistic height fog with a single height fog model. In order to achieve this result, the developer created an analytic height fog model combined with a precomputed atmospheric scattering model.
While the precomputed atmospheric scattering model performs numerical integration, storing the in-scattering and transmittance information into Look-Up-Tables (LUT), the height fog model calculates the fog directly when the scene is rendered.
Since Kojima Productions couldn’t find a satisfactory analytic solution for the height fog model, they developed it independently. In Kojima Production’s approach information about the sun like and the sky light us supplied to the height fog model from the precomputed atmospheric scattering model.
In sunlight conditions, the light is incident to the ground, and interacts with the atmosphere. The precomputed model generates the scattering information and stores it in the LUT. The height fog model then receives info in background radiation, sunlight and skylight from the precomputed model.
While the precomputed atmospheric scattering model used is nothing special, the LUT used is different from the typical model. The implementation used by Kojima Productions mainly uses Bruneton’s and Elek’s model with some optimizations.
Normally a precomputed atmospheric scattering model has in-scatter and transmittance LUTs, but Kojima Productions replaced the transmittance LUT with sunlight and skylight LUTs, because they want to feed the information for sunlight and skylight directly into the analytic height fog model.
Two weather types were precomputed, sunny and dense fog. They can be used as a base to express various weather conditions with no further precomputation required. Below you can check out a sample of the model.
In the gallery below you can see the result of the model and its components. The first image is the final result, the second is the background radiation, the third is the background radiation multiplied by a blending factor with the background, the fourth is the sunlight component and last one is the ambient light component. By summing up the last three pictures, the result is the first.
Finally, in the video below you can see a sample scene from the Decima Engine (which is the same used for the second trailer of Death Stranding) showing an aerial perspective from sunny to cloudy weather with the inclusion of an artistic atmosphere.
As a result, the team was able to achieve both a realistic aerial perspective and an artistic height fog with a single height fog model.
Semi-recently, Hideo Kojima provided an update on Death Stranding‘s development, mentioning that the game is currently running on PS4, and the studio is working on mechanics and story.
We do know that the game will be an open world action game, and that will have an optional online element. It also comes with a star-level cast, with stars of the caliber of Mads Mikkelsen and Norman Reedus.
For the moment, we’re still waiting for a release date, or even a more generic window. Yet we do know that it’ll be released on PS4.