Dev Blog #9: Environment

For the past few months we’ve been hard at work on what we hope will be a major refresh to the environment rendering. We’re nearing the end of our work, but we’ve got a few things that need to be tidied up, bugs to fix and testing to complete before we can ship it. We’re updating the terrain rendering with a whole new architecture, the sky rendering to a modern MIE-based approach and volumetric clouds. All of which are some of the most requested features.

In the meantime we wanted to share a bit of the behind the curtains technical detail about the work as well as some screenshots to whet the appetite.

Steam post image Steam post image

Terrain System

Original Game

Back in 1998-99 when the OG terrain system was built it was bleeding edge, state of the art stuff. Having the ability to draw a procedurally generated landscape the size of Europe at 30fps on PCs with less RAM in them than I have in my Garmin watch (and probably not much more CPU) was nothing short of incredible. That said, to achieve the impossible the team had to create a system that is very far from easy to work with, particularly on modern architectures.

The primary challenges with the old terrain system were that it draws everything in screen space - so all the math converts spherical coordinates, to linear world coordinates, and then into screen space. On modern architectures we get a lot of stuff for free, in particular triangle clipping, vertex, index and depth buffers etc… But the old school way was very manual, but more importantly there was no path forward to modern rendering techniques.

Modern Upgrade

So we needed a way to preserve the aesthetic of the original game while modernising the terrain pipeline so that we have a nice way to move forward. The next release will deliver the first phase of this work which achieves two main objectives.

1. Utilise a more modern Geometric Clipmap rendering technique, that moves a big chunk of the work onto the GPU. and;

2. Upgrade the procedural texture generation to maximally utilise the cores available on modern CPUs to dramatically increase the throughput of landscape tiles.

The main benefit of the new system is to improve the general quality of the terrain on “normal” mid-spec PCs, while substantially improving the performance (most noticeable in the lack of latency). Additionally we’ve got an excellent foundation to build on as we start to look a little into the future modernisations such as moving the procedural texture generation fully onto the GPU.

There’s obviously a lot more detail that we could include on the new terrain system and if there’s enough interest we can look at doing an in depth series on it.

Physically Modelled Sky

The old sky utilised a very simple (but effective!) traditional sky dome effect, with precalculated coloring and a very basic time of day simulation. We’ve upgraded the sky to utilise a pure GPU approach to generate a Bruneton-style physically-based atmosphere:

• Real Rayleigh + Mie scattering. Every pixel of sky is raymarched through a 100 km atmospheric shell wrapped around a 6,360 km planet, with proper exponential density profiles for both air molecules and aerosols. The result: authentic blue middays and warm reddened sunsets.

• Real celestial mechanics. The sun's position is driven by an ephemeris model from the mission's date, time and observer latitude/longitude — fly a December raid over Bremen and the low northern sun is in exactly the right place.

• Moon with true phase lighting. A spherical moon billboard is lit from the real sun direction with a phase-accurate terminator and faint earthshine on the dark limb. No stickers, no swapped textures.

• Procedural starfield. A sparse, hash-driven star distribution gives a believable 145-ish naked-eye stars across the celestial sphere, with stellar colour variation from warm K/M-class to cool A/B-class tints. Stars properly fade in and out across civil twilight.

• High cirrus layer. A 12 km procedural cirrus shell — well above the B-17's combat ceiling — gives the sky character without obscuring the action below.

• Authored once, used everywhere. The sun direction the sky uses is the same one driving terrain and aircraft shading, so highlights, shadows and atmospheric tint always agree.

Steam post image

Volumetric Clouds

This is the work that we’ve got most left to complete, and it will have a pretty large impact on gameplay. This is very much a work in progress so they’ll almost certainly change a fair bit but we’re liking the way they’re going. We'll write more about these when we're closer to shipping them.

Experimental Tooling

We’ve also been working on tooling to bring us closer to allowing community generated content for the game. Still early days on this, but these shots should give you a flavour of where we’re going.

Here at MicroProse we consider working on Mighty 8th Redux to be a labour of love. It serves as a real and direct link to our company’s history. Thank you for helping us bring this game to a new generation! Brave the deadly (physically modelled!) skies!