I like this solution. Good separation of concerns, as the designers can just keep playing around until the mood is to their desire for every area. And the editor that you guys have built up is fantastic. Would really love to see another article on the editor.

That sounds right Naty. Reading the engine code this morning, I can see that we had a system in place prior to using bitmaps, but it was 30 or so parameters, presumably attempting to reverse engineer the Photoshop filter. That’s almost certainly the system Tim was working on. We still use them, but for more designer sourced effects. They can be edited directly in-engine so they have a rapid iteration cycle, while our Photoshop & bitmap path is a bit longer as our textures are / were baked offline.

Eric had to re-write chunks of my effect blending code to get the two versions to co-exist. It looks like we convert the parameter based system into a colour cube, before doing the final blend.

Posting this and some of the earlier articles on the lightmapping to facebook has encouraged a whole bunch of lighting artists on my friends list to consider making the switch from animated films to games. Keep this up and you’ll start attracting some seriously awesome talent away from the film industry.

The stuff you’re doing here is SO freaking cool!

Aha – thanks for the explanation. That’s really clever!

Cool. I’ve stuck a note about this in the article.

There is not much point in exposing the editor for this game. It’s not like Braid where you could make more levels that make sense.

That strip in the top left is the colour mapping formula. The 32 squares are stacked, to make a 32x32x32 cubic texture. In a pixel shader, the RGB values generated from texturing + lighting are used to look up a point in this texture to discover the colour that should be written out. Red is right in a layer; Green is down in a layer; Blue moves across through the layers.

There are 256 possible values for each of R, G and B, but only 32 corresponding values in the lookup table. The graphics card fills the gaps by interpolating between as many as 8 different samples to give you the final colour. Fortunately, this is what the graphics card’s built for! The whole thing is a single texture lookup so it’s ridiculously fast.

That interpolation loses you some control… but because the texture itself is only 32x32x32, it takes up just 128kb or less of video memory, and you can afford to blend multiple colour look-up tables on the fly before each frame even on low-end hardware.

Phil – I came up with the idea shortly after I started working on God of War 3 – I think someone else at EA came up with it independently at about the same time. It’s a fairly simple extension of the ideas in http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter24.html though.

Colour grading tools can also help to evaluating the accessibility of your visual design for colourblind players (a not-insignificant percentage). You can use colour tables that simulate the reduced colour spaces of different forms of colourblindness. If you use colour as an important element of any puzzles, or as an indicator within your GUI, you should evaluate your colour choices in this way. For example, I demonstrated this technique using the Source engine’s colour grading tools here http://backslashn.com/post/7669124799/colorblindness-simulation-in-the-source-engine

http://renderwonk.com/publications/s2010-color-course/

However, our implementation is nice in the sense that it required *very* little development effort and is very easy for the artists to use. For example, UE3 requires you to crop the look-up table to input it in the engine. That not only takes time, but makes the tables much harder to identify. By keeping the modified screenshot by the side you can easily tell what effect the table was intended to achieve.

Thats more of a Tech/monitor problem :(

Please keep these coming, Although I’m not sure at what point I’m going to stop looking so I don’t spoil the game for myself!

Maybe you should put all of these posts plus more work in progress things into a book to come out after the game, “The making of” ( with a download code to get 3d files/videos to look at too!)

Well, our actual color grading will probably not look like my examples in this post… so that’s something.