Lights

Mayaseed translates spot-lights, point-lights and area-lights out of the box. Here's a few things it's useful to know when using lights in your scenes.

Appleseed lights have a quadratic falloff

Because appleseed is a physically based renderer, lights may behave differently to some other renderers. In practice, the most noticeable difference is that all lights will have a quadratic falloff so light intensities may need to be higher than you usually expect. You can also turn the falloff mode of Maya lights to quadratic by selecting the light and changing the decay rate to Quadratic in the attribute editor, this won't change the render behaviour in appleseed but might make make your viewport display look slightly more like the final render.

Point lights and spot lights are non physical

Currently, appleseed point lights and spot lights behave as infinitely small light sources. This can be handy but has the drawback that these lights cannot have soft shadows and may cause the render to take longer to converge.

Importance sampling

Appleseed does a very good job of spending more render effort on lights that contribute more to the scene than others but you may still find that sometimes one light in your scene seems more noisy than others. If this is the case you can tell appleseed to spend more time on the noisy light by adding an importance multiplier export modifier. To do this select the light and chose Mayaseed > Add export modifier > Lights > ms_importance_multiplier and turn the importance up.

Notice how the left light in the image below seems noisier than the light on the right; this is due to the light having an importance that is set too low.

Importance sampling

Area lights are the same as mesh lights

Appleseed has no native area light but as any surface can emit light we simply export area lights as a square polygon with an edf to appleseed.

Area light visibility

By default, area lights are invisible to primary rays by turning off the light emitting material's visibility. This can be handy if you need to place a light in front of the camera but in some cases can lead to noise in the scene. If you find that adding a light to the scene adds noise or fireflies, try adding the area ms_light_visibility export modifier to the light.