Area versus Mesh lights in Cycles

Does anyone have any information on how these might behave differently in Cycles (apart from visibility), and if there is a speed increase in using one rather than the other with some particular configuration? Obviously I am talking specifically of rectangular and square lane type meshes, not 3D object meshes!

Additionally, is there anything to be gained by subdividing a mesh light? Is there a performance loss?(This question is for any kind of mesh.)

I believe using arealights may be a tad faster if you don’t intend for your light to be visible to the camera, it’s also unidirectional out of the box so you won’t need to use additional nodes which might slow things down slightly.

The only thing you need to know is that you might need to use higher energy values and you can’t use edit mode to just scale it (you need to use the size values in the lamp settings). You will also want to make sure that you have MIS checked which will give cleaner light and allow it to produce caustics (providing you didn’t disable them).

Thanks for the info AceDragon wow, 18810 posts!

AreaLight = No Reflection on Glossy
MeshLigh = With Reflection on Glossy

AreaLight = MIS* on or off = no visual difference (off is faster)
MeshLight = MIS* on or off = big visual difference

AreaLight = little more noise
MeshLight = little less noise

AreaLight need 60x more energy than MeshLight

this was tested currently by me…

I use always MeshLight (quad),
this give best results

MIS* = multiple importance sample

Attachments

test.blend (113 KB)

TS1234 thanks for sharing your info! The bit about the MIS is very interesting! Have to check it out. I have a bad habit of surfing the forums while a render is running so I can’t say exactly how careful my measuring times procedure is, that’s why I love to get other people’s takes on speedup.

It’s curious that mesh light intensities or performances seem not to be sensitive to number of vertices…