Lighting in RenderMan is flexible but also very straightforward for users.
RenderMan includes a set of basic geometric lights, built-in. These specialized shapes - DomeLight, DistantLight, RectLight, and SphereLight (particularly the latter two) - can provide superior sampling behavior, compared with arbitrary geometry (i.e. standard geometric primitives with a light Bxdf attached). There's also a PortalLight to improve lighting interior scenes lit indirectly through openings like windows and skylights as well as a Daylight simulation.
Note that due to these optimizations, the spherelight requires that all scale transforms be uniform, e. g. X,Y, and Z scale must all be the same so as not to skew the sphere shape into an ellipse or other form.
Note there are three main ways to light a scene:
- Analytic Lights - These are the preferred choice. These provide superior memory usage, flexibility, and speed.
- Mesh Lights - These are great for using arbitrary shapes in lighting. These consume more memory since they are geometry and complex shapes may increase noise.
- Emissive Surfaces - These typically use a constant bxdf or "glow" parameter to light a scene indirectly. This is inefficient and should usually be avoided but may be useful for texture mapping "lights" onto futuristic objects and panels!
Analytic Light Types
- PxrDomeLight - The domelight acts as the environment light for a scene and is often mapped with a high dymanic range image (HDRI).
- PxrRectLight - The rectlight is the commonly used rectangle-shaped area light.
- PxrDistantLight - This light is perfect for use as a Sunlight or other distant source where light rays are nearly parallel and cover the whole scene.
- PxrDiskLight - Great for using as an area light or in combination with filters to make a spotlight.
- PxrSphereLight - For users that miss using a point light, this light can be useful to illuminate in all directions.
- PxrEnvDaylight - A daylight simulation shader where you can supply any time and location on Earth or simply place your sunlight where you like it.
- PxrPortalLight - For difficult lighting situations like indirectly lit interiors, this light along with the PxrDomeLight can be used to increase the quality and speed of your renders.