Real-time DYNAMIC GI / Radiosity running at 60 fps!!!??

[Richard McCarthy]

I recently came across this interesting term (I think from ATI press release), and I am not that technical savvy (especially code savvy) so I don't quite understand how this works.

 

 

"Spherical Harmonics & Precomputed Radiance Transfer"

 

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directx9_c/directx/graphics/TutorialsAndSamples/Samples/PRTDemo.asp

 

http://www.ati.com/developer/gdc/GDC2005_PracticalPRT.pdf

 

From what I can understand it is a method of pre-calculating the energy transfer (light energy) and store it on geometry/vertices as a method of fast table look-up.

 

So if any 3D engine coder would enlight us all and tell us in layman's term how this work I would really be appreciated.

[Pablo Zurita]

Yeah, it’s something like that. First of all, it’s not stored at the vertices of the geometry but stored at each voxel of octree. With the position of the object, and the values at the objects you can reconstruct the lighting for that object. Based on that, this isn’t exactly real-time GI (please don’t use the word “radiosity”, radiosity is a technique that simulates diffuse inter-reflections of lights). The values are not being recalculated in real-time; it’s just a query to the voxels in the octree and rebuilding the lighting from there. So, this technique only really works for “small” dynamic objects such as characters in a game, and little objects that don’t affect the lighting of a scene too much or else it will look unrealistic.

[seismograph]

well just one comment about all these demos:

 

I don't know any demo which uses concave forms to demonstrate the ability to use hdri, Gi or radiosity in Realtime.

Forget all the crappy "one object" demos if you want to do architecture or anything which have to do with rooms.