Best approach for office ceiling lights - vray plane lights or vraylightmtl?

[tricky]

In a large, open plan office space, with something like a Cat5 lighting grid (600x600mm light every 2400mm for instance), what is the best approach with vray these days (version 2.4 and version 3)?

Creating a low subdiv vray plane light for each one (maybe subdiv=4) or creating a plane for each light and assigning a vraylightmtl?

[joconnell]

An actual light will always sample far quicker than a mesh light.

[tricky]

But what about just a simple 2d plane with a simple vraylightmtl applied? So it isn't really a mesh light...or is it???

[joconnell]

Yep, it's a mesh. Vray isn't able to tell that its only a single polygon plane, it still sees it as a mesh that it has to evaluate without the same optimisations as the vray light. Try it yourself with a vray plane using the sample rate and raw light pass, then try a plane with a light material and direct illumination turned on. Match your multiplier in the light material and the subdivs in the direct illumination to your vray light and see which one comes out quicker and cleaner!

[Morne]

If it's a large area you could stick in a plane the size of your light with light material (or texture that looks like the actual fitting). Make sure direct illumination is switched OFF. Then stick in one BIG Vray Plane Light that covers the whole area and make it invisible and switch off affect reflection and specular