What lamps are OK to use in Cycles?

In Blender 2.72, what kind of lamps are OK to use in Cycles? I’ve read conflicting information on the forums as far as what sort of lighting is OK to use. Are Point Lights OK? Sun?

What downsides are there to using Blender’s lamps in Cycles? Should I just stick with objects with emission materials?

Thanks!

There’s nothing necessarily wrong with any of them. Except the hemi light, that doesn’t exist in Cycles and exports as the sun lamp. Some things to keep in mind with each lighting type:

Point - Acts like a spherical lamp with the radius equal to the “size” parameter. The default (10cm) loosely approximates a globe lamp. Use smaller sizes for a bare bulb. Using size=0 will make it infinitely small, which makes no sense in reality and gives perfectly hard shadows. When people say “point lights are bad” this is usually what they’re referring to. Do not set size to 0 unless you have a specific reason to do so, it almost always looks awful.

Spot - Spot is a point light that only shines in a particular direction. People have a habit of misusing these for things that should be done with area lamps, such as desk lamps or track lighting. Spots only really work for things like stage spots, flashlights, and car headlights which have actual mirrors or lenses to focus the beam. Something with a diffuse backing like a desk lamp behaves completely different and is best approximated by a mesh/area lamp over the front. The “size” property on the spot approximates the aperture of the lamp housing. Like the point lamp, 0 is non-physical and looks bad in most cases. The size option will also automatically feather the lamp edge correctly, the “blend” option is a non-physical extra penumbra. Consider setting blend=0 and size!=0 for best results.

Sun - Sun is a light source an infinite distance away. If you object is so far away it might as well be infinite such as the sun or another celestial object (moon, alien planet in the sky, etc) use this. If your object is NOT astronomically far away from the scene, do NOT use the sun lamp. Use a spot or area lamp. The size prop shows up again, but on the sun lamp it controls the angular diameter of the light source in the sky. Tbh, I’m not sure how Blender converts the distance value into an angle. For sunlight, you want a very small but non-zero value. (once again, 0 is non-physical and only works well in special cases). Something like a planet in a moon’s sky will be a lot bigger and softer.

Hemi - this is a sun lamp, you might as well just set it to sun

Area - this approximates a glowing plane (similar to a plane with an emission shader, but it only shines in one direction), the size property determines the dimensions of the plane. Size=0 is meaningless for an area light and will disable it.

Mesh lights (objects with emission shaders) - These are just area lights with arbitrary shapes. There are a few differences worth noting. For one, mesh lights currently lack the max-bounces setting that is available on area lamps. Second, mesh lights can be visible to the camera, area lights never are. (uncheck “camera” in the ray visibility rollout if you don’t want this on your mesh light). Third, in 2.73 Cycles uses a more advanced area light sampling scheme, this is not supported for mesh lights. Finally, if you are using the branched-path tracer, light/shadow sampling for mesh lights is set globally for all mesh lights in integrator settings. Area lamps can be set per-lamp.

In older versions of Cycles, lamps did not support MIS while mesh lights did, which is why you might have seen advice to use mesh lights. This is no longer true, area lamps offer superior performance and options with the same physicality as mesh lights. Mesh lights in exchange offer much more control over the shape of the light.

The information will, I believe, be less conflicting if you note A) the fact that Cycles is in ongoing development with regular updates to what is supported and B) the dates of those posts on the forum.

Thanks, J_the_Ninja – it’s helpful to know what the current state of Cycles lighting is.

would be nice if area lights could simply show up in rendering as well. one still needs to add a mesh for that.