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View Full Version : Getting the light intensity at a point

paulselhi
08-09-2006, 04:46 PM
I realize that i can use the plight node in TP to calculate the intensity of light at a given point but i can only do that for a specific light

Is there some way in expresso that i can get the overall light intensity at a given point, i mean the intensity of illumination at that point from all light sources

The idea would then be to have a non rendering plane infront of the camera which measures the light intensity going into the camera, i could then use that info to automatically adjust other paramters

I may be off targrt here but i was thinking maybe you could use that info to drive say the color mappng thus a camera would react to changes in lighting say from going from a room to a street in much the same way that a real vid camera can adjust

Of course it would be even better if this could be extended to take Gi into consideration

is this possible ? i think i could do a basic setup using plight but as i said it does not take the overall lighting into consideration
georgedrakakis
08-09-2006, 10:21 PM
hey paulselhi, maybe this will help you:

http://forums.cgsociety.org/showpost.php?p=468124&postcount=1


once upon a time i wanted to make a plug about real-world lighting and that feature would be very usefull, but unfortunately the link for the lightmeter (inside the thread) is dead.

cheers,
george
paulselhi
08-10-2006, 07:48 AM
Thing is the info is there in c4d somewhere, it is essential for a render !!. Things like AO use it and of course GI uses the info

I think you could use several plight nodes and get an avearge but it would only be good for non gi renders as plight works on direct lighting not bounced light

there must be some way to get the light intensity on an object and use that as a measure of how much GI lighting it has, you could then use that info to drive the color mapper, you could not really use it for anything else as any changes that are not post will actually effect the original reading and thus create a loop ( er.. you could of course have one plane in front of the camera, invisible, which actually does the measuring and then one closer to the camera who's transparency is based on the reading taken from the detector..hmm not sure if transparency will be the correct way to go ? "

As i said all this info must be there to create a final render so it is a question of somehow accessing it before the colormapping is applied

talking of feedback loops have you looked at LW9 recently ? It has a cctv camera shader which you aplly to say a series of planes, this shader can take the view of any camera and apply it as a material - live

So you can have an object surrounded by planes and several cameras looking at it, you make each plane have a cctv view from one camera, and animate the central object. The views on each plane will be what it's cctv camera sees and this will of course see other planes as well so a cctv shader will have mutiple images on it, views of views like a mirror hall..oh gets freaky !!!
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