Inspiring game artist and distinguished photographer Mukul Soman (Linkedin) shared some of his ideas on building amazing skyboxes. Mukul is currently with Monolith, but a couple of years ago he worked on the skyboxes for Halo 5. It’s an amazing breakdown, which talks about the building of virtual skies, the lighting, the clouds and other little details
I am currently working with Warner Brothers Games as a senior world artist. In the past I worked with studios like 343 Industries and Turn10 studios. I worked as a Skybox Artist on Halo4 and Halo5. I had taken on the role of a cinematics artist as well during my stint at Turn 10 working on creating in engine cinematic content for Forza Motorsports 5. You can see some of my work at www.mukulsoman.com
The Production of Skyboxes
This a very vast subject but I will try my best to condense it in a short format. I am usually very organic in my approach since most of the sky-boxes I built for the Halo games had only mood boards and no real concept art to reference. So I had to pretty much come up with the concepts and then go ahead and build the skyboxes. I usually start with making the sky texture and then work my way closer and closer to the level. The mid ground and foreground areas usually have actual geo for terrain elements which I build using world machine, Geoglyph & Zbrush. Once thats all in, I texture and then light the elements I just put together in the skybox environment using 343’s proprietary tools and also drop in cards with scrolling UVs to have moving clouds and fog elements which really help to tie in all the terrain and vista elements & the sky into a cohesive unit.
Multi-layered skyboxes are no different from regular skybox work but like you said depending on the needs they might have to be animated in different ways. For example, on Halo 5, I had to work on a space elevator sequence where the player has to go from space all the way to the surface of a planet. Now that was not an easy problem to solve because no one really knew how exactly to solve this issue because it had pretty much never been done before in a game. It was a great problem solving exercise for me! What we ended up doing was, I made 3 skyboxes (one for the planetary view from space, one for the stratospheric level and one for the terrain level) one below the other and the animation team animated them upward, which made it look like the elevator moved downwards. The parts where there was a hard transition from one skybox to another, we made the elevator go into a covered section so that the transition will be appear to be seamless to the player.
My pipeline varies according to the needs of a particular skybox but for most part my workflow starts off with making a base sky in Vue or Terragen & then adding photographic elements and painting onto them in photoshop. Then I move on to the terrain which starts off in world machine & geoglyph and goes through Zbrush and a bit of back and forth before a final pass from world machine gets me all the macro maps that can be used to control material distribution. from there on its pretty much the regular low res to high res baking workflow thats done in games since forever. For texturing I use Mari a lot because of it’s great painting with masking features that allow me to help making my own maps that work coherently with the maps I got of world-machine.
Clouds provide great opportunity for movement and a sense of atmosphere. They are critically important to make a skybox look believable. I create my clouds either procedurally using Vue or Terragen or by using photographs and extracting the clouds out along with an alpha map using photoshop and then mapping them onto a card geo and then strategically placing and blending them into the sky using vertex alpha functionality. Movement is then added using shaders with Uv Scrolling functionalities.
The real key to moving elements in skyboxes to look believable is to keep the movement subtle and not too exaggerated. Skyboxes usually contain elements that are massive and far, so tend to move slowly. While placing such elements in the sky its also important to follow the compositional clues that can be picked up from the over all level too so that the player is not too distracted and overwhelmed with detail and movement.
Most of the lighting I did was baked lighting. I chose to do it using 343’s proprietary tools. I was mostly making lighting decisions using my own photography as a reference. There no such thing as “Correct” lighting especially for skybox elements. They just need to look good and believable and as long as they do that and doesn’t break anything else in the game, it doesn’t matter if they are actually correct or not. In short they should be looking believable and must blend in seamlessly with the lighting of the rest of the level.
Importance of Sky
From when I was a kid I used to stare into the sky and wonder what lies beyond that sky. The fact that the clouds and the sun and the stars are all so far away makes us want to imagine things about them and awaken a sense of wonder in us. As far as video games are concerned, Sky’s take up pretty much half of the screen in any outdoor game and hence they become a very critical tool for establishing mood & drama through careful use of color tones, shapes and depth.