Cycles - lamps or object-based lightng?

So I was wondering if it was better to use lamps or object based lights in Cycles. Or is there maybe times when one is better than the other, say for an outdoors scene? I really have no idea :stuck_out_tongue:

Any help would really be appreciated :slight_smile:

Lamps can be sampled only using “Direct light”, as you cannot hit infinite small point. Mesh lights can be sampled by both methods, indirect light and direct light. Cycles probe random light every bounce, more lights = more noise.

Ideal setup for Cycles - no lamps or emission meshes at all, scene light only by almost constant background, all scene is simple open plain with some object on it, like car on floor.

In closed indoor scenes, as probability to background is very small (only through small window), you better use mesh emission quad right outside window, or single point/ spot lamp inside room.

In general, prefer background, then emisson mesh, then lamps, and try decrease lamp number.

As of 2.65, the best option is easily mesh lights.

In 2.66 however, the regular Blender lamps are now capable of multiple-importance sampling or MIS, and thus are capable of producing the same effects as meshlights (caustics ect…).

If you’re doing a realistic interior scene for instance, then meshlights are a must, however, more abstract scenes might benefit from the generic lamp types as they generally do not always require the lightsource to be visible (unlike meshlights where you would need to use a node setup with lightpaths).

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No, you don’t need a node setup with light path to make a mesh light invisible.

Object panel --> Ray Visibility tab (at the bottom) --> Disable Camera.

Simple at that…

True, if you’re using a standalone emission object.

If your emission material is incorporated into a mesh with multiple material indices (this is what I do a lot), then you need to use the light path node as the Ray Visibility options affect the whole object (which you might use sometimes because it is faster).

In that case, yes. You need to deal with light paths. But it’s not that complicate. I can do it even without seeing the Node Editor.

A Light Path node, a Transparent shader, a Mix shader. You plug “Is Camera Ray” as mix factor, the Transparent shader at the bottom and you group the 3 nodes. You pull and plug the 2 free sockets on left and right and you get a “plug-in” to drop on the noodle just before “Surface” of any material that you want invisible to the camera.

Any way, all this will become irrelevant when BI lamps and emission materials will be treated equally in Cycles. Soon, according to what I read… somewhere I don’t remember.

Using nodes to create invisible lights is the least efficient way to work in Cycles. You might want to check this article in the official Wiki, specifically the parts about transparency and ray visibility. When using the transparent shader, although rays are cast as if there was no geometry, the shader has to be actually executed. Ray visibility checkboxes, on the other hand, help increase render speed as the object gets skipped from ray traversal.