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What Is Sample Light?

A Dive Into Rendering!

Related Questions

So, what is sample light? You may be confused about the term, but don’t worry because we have all the answers to your query!

So, let’s start!

What Is Sample Light?

Sample light is the light source or light type in light sampling. It is pretty self-explanatory in its meaning. A sample of light.

We use light sampling in rendering videos.

Control Over Sample Lights

Control Over Sample Lights
Control Over Sample Lights

When working in the ‘RIS’ mode of ‘PRMan,’ the light sampling process is intended to be as straightforward and uncomplicated as is humanly feasible. The integrator is primarily responsible for controlling how the sample lights distribute. When creating the sample lights for the integrator, the two principal built-in integrators, ‘PxrVCM’ and ‘PxrPathTracer,’ offer slightly different interfaces.

The integrator normally manages the lighting system in RIS by using a single sample count requested by the integrator. The integrator usually comes with a ‘numLightSamples’ parameter subjected to a specific sample reduction when the ray tree traverses itself.

The system will typically automatically divide the samples per this budget. Because of this, the user is relieved of directly controlling the sample count. However, there are certain circumstances where automatic balancing may not be desirable.

These include instances in which the system cannot effectively automate the selection, and the user expressly requests that particular lights take on the responsibility of assigning a sample count. You may accomplish this by including the ‘fixedsamplecount‘ parameter in the call to the emit() method of the appropriate light.

In most cases, the software will remove the fixed sample count light from the automated sample selection process. Also, the software will give it the requested sample count. This indicates that the budget for automatically balanced samples equals the effective sample count defined by the ‘numLightSamples’ variable. In addition, the software will collect the total number of requests for the fixed sample count.

Suppose an integrator disregards this request as the ray depths grow or as the route significance drops. In that case, it will again consider the lights to share the available budget for automatically balanced samples.

Integrator Controls

Integrator Controls
Integrator Controls

Controls for ‘numLightSamples‘ and ‘numBxdfSamples’ may be found in ‘PxrPathTracer’ and ‘PxrVCM’, respectively. Light samples are selected according to the significance of the light, and they can effectively capture diffuse and glossy reflections.

It is less probable that these samples will ‘align up’ with the peak if the Bxdf lobes are tight. You can use the usage of multiple importance sampling to resolve such characteristics. The software obtains samples from the lights and samples their significance according to an important metric applied to them.

The software brings them together to form the completed product. We recommend you set the sample count for numLightSamples and numBxdfSamples to the same value in most situations.

The photos that follow demonstrate, in order, multiple importance sampling, light-only sampling, and Bxdf-only sampling. Nearer to the camera, the lights change in terms of both their size and the color temperature they emit, and the surfaces become smoother. Finally, the Bxdf (PxrDisney) has a specular component as well as one that is diffuse.

Final Words

So, that was all for today. We hope you found this article useful.

Written by:
Editor-in-Chief and lead author at WhyDo