Date: Fri, 29 Mar 2024 08:52:08 +0000 (UTC)
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Subject: Exported From Confluence
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Lighting in RenderMan is flexible but also very straightforward =
for users.
RenderMan includes a set of basic geometric lights, built-in. Thes=
e specialized shapes - DomeLight, DistantLi=
ght, 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 impro=
ve lighting interior scenes lit indirectly through openings like windows an=
d skylights as well as a Daylight simulation.
Light Filters can als=
o be used to modify and direct the lighting with even more control and arti=
stic options. You can find real-world possibilities like Gobos and Cookies as well as advanced ways to link and control res=
ults like object specific =
intensities from a single light.
Note there are three main ways to ligh=
t a scene:
- Analytic Lights - These are the preferred c=
hoice. These provide superior memory usage, flexibility, and speed. Their v=
isibility is a simple on and off for camera visibility.
- Mesh Lights - These are great for using arb=
itrary shapes in lighting. These consume more memory since they are geometr=
y and complex shapes may increase noise. These can make use of visibility l=
ike any other object: camera, shadow/transmission, and indirect visibility.=
- Emissive Surfaces - These typically use a c=
onstant bxdf or "glow" parameter to light a scene indirectly. This is ineff=
icient 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 m=
apped with a high dymanic range image (HDRI).
- PxrRectLight - The rectlight is the commonly used rectangle-shaped area light.
- PxrDistantLight<=
/strong> - This light is perfect for use as a Sunlight or other distant sou=
rce 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 mak=
e 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 loc=
ation on Earth or simply place your sunlight where you like it.
- PxrPortalLight - For difficult lighting situations like indirectly lit interiors, t=
his light along with the PxrDomeLight can be used to increase the quality a=
nd speed of your renders.
Geometric Light Types
- PxrMeshLight <=
/strong>- The mesh light uses a piece of geometry and turns it into a light=
source. This is much more efficient than using glow or emission from a bxd=
f. It's great for things like neon lights.
Utility Light Types
- PxrAOVLight=
- This is a utility that's recognized as a light type but it doesn't=
em> illuminate anything. It's a useful tool for creating quick masks for ob=
jects through light linking.
Lights also have some special parameters regarding shadows and bidirecti=
onal path tracing made possible by the PxrVCM and PxrUPBP integrators. You =
can refer to the technical memo:
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