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Global Illumination Research Pt 3


Josh

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The environment probe feature is coming along nicely, spawning a whole new system I am tentatively calling "Deferred Image-Based Lighting". This adds image-based lighting to your scenes that accentuates the existing deferred renderer and makes for higher quality screenshots with lots of next-gen detail. The probes handle both image-based ambient lighting and reflections.

 

Shadmar helped by implementing parallax cubemap correction. This provides an approximate volume the cubemap is rendered to and gives us a closer approximation of reflections. You can see a good side-by-side comparison of it vs. conventional cubemaps in Half-Life 2

. It works best when the volume of the room is defined by the shape of the environment probe, so I changed probes to use a box for rendering instead of a sphere. The box is controlled by the object's scale, just like with decals, although I wonder if there would be a way to build these out of brushes in the future, since our CSG building tools are so convenient. In the screenshot below you can see I have added two environment probes to a map, one filling the volume of each room. Placing probes does require some amount of artistry as it isn't a 100% perfect system, but with a little experimentation it's easy to get really beautiful results.

 

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Once probes are placed you will select a menu item to build global illumination. GI will be built for all probes and the results are instantly visible. The shot below is only using an environment probe for lighting, together with an SSAO post-processing effect. Because the ambient lighting and reflections are image-based, any bright surface can act as a light even though it isn't really.

 

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When combined with our direct deferred lighting, shadowed areas become much more complex and interesting. Note the light bouncing off the floor and illuminating the ceiling.

 

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The new feature works seamlessly with all existing materials and shaders, since it is rendered in a deferred step. It can be combined with a conventional ambient light level, or you can set the ambient light to black and just rely on probes to provide indirect lighting.

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What are these probes? Are these things that we have to place in our scene in strategic areas and only do things in a certain volume?

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