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Hans Jakob M?ller

Radiosity, area light render times

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Geomerics claim that their tecnology can render a scene with radiosity in 1/100 of a second, that is realtime with any up to date video card from ATI or nVidia. http://www.geomerics.com/enlighten-why.htm

Why is it that renderworks takes two days to calculate a radiosity solution for a simple scene with four walls, a floor and a roof and some windows? And when finished you discover that the image is far too dark, far too light or full of artifacts. Even a simple scene with an area light outside the windows to simulate daylight takes a day to render even without radiosity!

Why doesn?t renderworks use a similar technology as Geomerics if it?s actually 10 million times faster? Maybe more realistic, when will we see a radical increase in render speed on realistic lighting in renderworks?

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With 2008 and Final Gather support, you can render a scene part of the way with Radiosity and finish with Final Gather, cutting your rendering time almost in half. Alternatively, Final Quality RenderWorks with Final Gather is just as impressive as Radiosity with Final Gather, and renders in even less time.

I'll post some examples and time trials shortly.

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Order the SDK and read the documentation, because the devil is in the details.

Geomeric's claim of "100 fps" is based on a cached, precomputed solution rather than a real-time solution. It also assumes 72 DIP output. The SDK further notes that they are approximating radiosity rather than producing a true radiosity solution.

Finally, take a look at the high resolution screenshots on the Geomerics website, remembering that these screenshots are intended to show the capabilities of Enlighten to their best advantage, and ask whether the image quality is acceptable for professional purposes.

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I built a simple model about 6x5 meters with four white walls, a white ceiling, a floor with wooden texture, one big window, a table with four simple chairs and a directional light. With the proposed object size and first detail at about 1 m rendering time is acceptable but creates ugly atifacts, especally at the top and bottom of walls. If I reduce object size and first detail to about 300 mm the artifacts are still there, just smaller scale. To get a reasonable result it seems I have too use the smallest possible values for object size which results in rendering times amounting to days. Then it?s very hard to evaluate by trial and error. Is it really worth spending time on? Is there an optimal setting for a room of this size with details the size of window frames, table legs etc. or is there some trick that I`m missing?

Edited by Hans Jakob M?ller

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I spoke with Dan Jansenson, the author of the RenderWorks Recipe Book (www.imageprops.com, I hope he will finish an update for VW2008).

He suggests that you need to consider a rendering a stage that requires artificial lighting techniques.

Directional lights don't work the same way the sun does. A better solution would be to eliminate the direction light and put an area light (rotated to vertical) in the window.

Pat

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