OTOY Forums

Hello,

Can you please explain, surface brightness option to me? I've read the documentation and it isn't acting like the way it says. No matter if option is on or off, changing the size of geometry changes the amount of light emitted. Also the brightness of object is constant no matter if option is on or off. Only difference I see is that when surface brightness is on, more light gets emitted.

Hi,

You have a good information about all the emission nodes parameters in the Standalone docs. I'm not sure if you have seen it:
https://docs.otoy.com/Octane_Render_Sta ... g%7C_____4

Surface Brightness
If enabled, ‘power’ specifies the brightness of the surface, and not the total emitted power. This is useful when the brightness of the emitter is independent of the area of the surface.

Enabling this option will cause emitters to keep the surface brightness constant independent of the emitter surface area, i.e. the total emitted power will be dependent on the emitter’s surface area. The scaling is done in a way that a texture emitter will produce the same colour in the rendering (if the diffuse channel is black), when the camera response curve is set to “Linear/off”, exposure to 1, gamma to 2.2 and vignette to 0. Disabling the option will keep the total emission power constant, i.e. the surface brightness will become dependent on the emitter surface area.

Perhaps your problem could be also that you don't have the diffuse channel black, so the emitter surface is also working as a conventional diffuse object, not only as a light emission surface.

Hope this helps,
-Juanjo

Hi Juanjo, I did read the documentation but octane doesn't apear to act like the documentation. I've attached a sample scene file. In it, both with and without surface brightness option behave a same way. The only difference is that when it's off, it's emits slightly more light.

hip file: https://1drv.ms/u/s!AnP3YxWnbl-NvyX-QKBHMaE0q2dI

I figured out the problem. I was changing scale at the scene level vs geometry level. Apparently when using global transformations, surface brightness option does't work.

Ah, yes. Thanks for the information. Yes, it seems that this feature is not designed to work with the object transformation at OBJ scene level. It works over the base mesh, at SOP level.

Thanks,
-Juanjo