tlehnhaeuser Posted March 26, 2009 Share Posted March 26, 2009 OK, its official, I'm lost.... OK nobody say anything! For the life of me I can't figure out how to get rid of the blotchuness in renderings when using Full Global Illumination. Can anyone shed some light as to what option controls this? I though it was photons but I guess not. Thanks Tom Quote Link to comment Share on other sites More sharing options...
IronKevin Posted March 26, 2009 Share Posted March 26, 2009 Try setting the Quality to high Shadow quality to 1 Precision to 3 Quote Link to comment Share on other sites More sharing options...
tlehnhaeuser Posted March 26, 2009 Author Share Posted March 26, 2009 Try setting the Quality to high Shadow quality to 1 Precision to 3 23963[/snapback] Well you may be right however I cant tell since my system is not strong enought to render this in a timely manner. Maybe when I get a 64 bit machine Quote Link to comment Share on other sites More sharing options...
Guest EricFoy Posted March 28, 2009 Share Posted March 28, 2009 Hey Tom... can you post your file and let us have a go at it? Quote Link to comment Share on other sites More sharing options...
tlehnhaeuser Posted March 30, 2009 Author Share Posted March 30, 2009 Hey Tom... can you post your file and let us have a go at it? 23978[/snapback] Hi Eric, sorry don;t have, it was a test file. However it was merely a Sphere on a Block with Full Global Illumination on using the "Kitchen.hdr" background found in the IronCAD images folder. Thanks Tom Quote Link to comment Share on other sites More sharing options...
Bryan Cargill Posted March 30, 2009 Share Posted March 30, 2009 (edited) The problem can occur with both full gi or background illumination. They both use the background image to light the scene. With some images, this can yield blotchy, disco ball effects at low sample rates. Side note- the difference between these two gi modes is that only Full gi automatically includes indirect illumination (radiosity & caustics). All other gi modes do not include automatic indirect lighting. Full gi will include indirect lighting resulting form the environment. Turning on 'photons' will also include indirect lighting from other light sources (spotlights, area lights, etc). If you wish to see indirect lighting (Radiosity & Caustics) in all other rendering modes besides full gi, you must manually configure lights as independent, indirect light sources. With this approach you can get great caustics and radiosity effects in any render mode-- even without GI! Spot lights are great for this purpose becasue they efficiently focus the effect. See the GI page of the light properties. The blotches are becasue the light hitting a point is computed by taking several samples of the background. If you only take a few samples, you will get a noisy result if there is a high variability in the colors of the background image. More samples (higher GI Quality) will average out the noise-- at the obvious expense of longer render times. So, the simple answer is to increase the GI quality. Note that using the 'studio' backgrounds will usually not give you this issue. That is becasue they are generally simple, smooth images made with lighting in mind. You may wish to try using Colored Illumination. With it, you can choose a single constant color to represent the background light. You should choose a color that is roughly the average color of the background image. This is perfect for outdoor scenes where light seems to come from everywhere. Remember, however, that you only get the easy environmental radiosity with full gi. To get radiosity in other rendering modes you must set up lights specifically for indirect lighting. In the future, IC will support using a different image for the background image vs the background lighting. When that is possible, the solution will be simple. You will use a less detailed, blurry version of your image for the lighting. This will in effect pre-average the background. This will give you better control over the process, but will require a little more work on your part. You can do something similar today, although it requires a more manual approach. You may create and use a (very) blurry version of your desired background image when rendering. Your noise issues should be minimized. Then, when rendering mask-out the background. You may then post-process your highly detailed background back into place. The problem with this approach is that any reflections or refractions of the environment will be of the blurry image! This may or may not be a problem depending on the circumstances. Hope that helps! Edited March 30, 2009 by Bryan Cargill Quote Link to comment Share on other sites More sharing options...
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