Monday, March 15, 2010 at 8:09 AM |  
I have completed porting directional shadow casting and refraction to the new system. This means we now officially have all the original features running with a deferred lighting renderer. A test run with all features on (single shadowmap, HDR and Refraction) got me an average of 40fps at 1024x768. Overall, that's pretty much a 10fps dip from previous test. This is mostly due to the shadow casting cost which shows how expensive shadow rendering is. I'm a bit disappointed with this since it makes PSSM useless even on fast machines. I'm planning to have a way to allow artist to define non shadow casting batched entities in the editor to narrow down shadow casting to where it matters. Hopefully this will improve shadow casting performance.

Aside from that, I've also changed the depth G-Buffer format into PF_FLOAT16_GR to add one more channel for material ID. I came to the conclusion of needing this due to the limitation of any deferred renderer which is having different materials with different lighting properties. The main reason I added this functionality so soon was that our tree leaves and grasses are using custom shading. This limits us from utilizing the deferred lighting system to lit them. It would be fine for the first level since there's only one light through the whole scene. However, we have plans for night scenes in the future which wouldn't work very well then. Hence with material ID introduced, the custom shading for leaf and grass is now done in the deferred stage. Obviously this potentially allow us to extend it even more into other types of materials like cloth.

Unfortunately since we are trying to limit the G-Buffer's fatness, we're limited with the number of channels we have to store data. This means that any material type that requires extra info cannot be integrated. Unless we introduce 64bit buffers, this is not possible.

At any rate, with this done, our artist can now happily do outdoor night scenes that has lights affecting grass and tree leaves. My next move is to get the major feature of deferred lighting in: spot and point lights. Since this blog post is already getting long, I'll leave my local lighting thoughts to my next post. So stay tuned. ;-)
Posted by Lf3T-Hn4D

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