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I was surprised to see the following emitter behavior. It's highly likely that my personal light physics is messed up.

If I have a mesh emitter 1 square meter in size at power 300, it should produce x lumens of output on a given subject. If I move the emitter twice as far away, the effective lumens on the subject should be 1/4. However, If I scale the emitter 200% but maintain the same distance to the subject, I should still get an x lumen output light (although it is likely illuminating more of the scene). Octane, however, seems to scale the power with emitter size. I don't know to what ratio it does this scaling, but the light is unmistakeably brighter. In my mind this is incorrect behavior. Anybody care to correct my light physics, or confirm this "issue"? Perhaps I have a setting unknowingly set wrong. Cheers!

aturbanotoy wrote:I was surprised to see the following emitter behavior. It's highly likely that my personal light physics is messed up.

If I have a mesh emitter 1 square meter in size at power 300, it should produce x lumens of output on a given subject. If I move the emitter twice as far away, the effective lumens on the subject should be 1/4. However, If I scale the emitter 200% but maintain the same distance to the subject, I should still get an x lumen output light (although it is likely illuminating more of the scene). Octane, however, seems to scale the power with emitter size. I don't know to what ratio it does this scaling, but the light is unmistakeably brighter. In my mind this is incorrect behavior. Anybody care to correct my light physics, or confirm this "issue"? Perhaps I have a setting unknowingly set wrong. Cheers!

that is correct. pos/rot/scale transformation are done without actually rebuilding the geometry but internally in octane, means you can translate mio poly meshes without notable delay; unfortunately this has the observed effect on emitters. currently the only way to overcome it is to have the mesh in the correct size (=without extra scaling). at some point around 2.0 the plugin will add an additional switch to every node to allow or disallow realtime transforms individually, so you can turn it off i.e. (and esp.) for emitters. as emitter meshes are usually not all too heavy, the additional time needed for rebuilding them is most probably negligible. on the plus side this also allows (again) to collapse meshes for "final" rendering to gain better speed (currently this is prohibited when scaled light emitting meshes are used)...