---
title: "Light Cache Settings"
canonical: "https://documentation.chaos.com/space/VRAYHOUDINI/113281034/Light%20Cache%20Settings"
format: markdown
---
This page provides information on the Light Cache in the GI tab.


## **Overview**

---

These options control the **Light Cache** settings for the** secondary diffuse bounces** in the [GI rollout](https://docs-chaos.atlassian.net/wiki/spaces/VRAYHOUDINI/pages/113279796).


## **Light Cache Parameters**

---


> Macro (anchor)



---


### **Example: The Subdivs Parameter**


<span style="color: #000000">The </span>**Subdivs **parameter controls the number of rays that are shot into the scene, and the "noise" quality of the light cache samples.

<span style="color: #000000">Here is a scene rendered with different settings for the </span>**Subdivs **parameter, all other settings are the same.

<span style="color: #000000">As we add more samples, the noise is reduced, but the render times increase.</span>



> Macro (anchor)



---


### **Example: The Sample Size Parameter**


<span style="color: #000000">The </span>**Sample** **size**<span style="color: #000000">** **</span><span style="color: #000000">parameter controls the size of the individual light cache samples. Smaller values produce a more detailed lighting solution, but are noisier and take more RAM. Larger values produce less detail, but take less RAM and may be faster to calculate.</span>

<span style="color: #000000">Here is a scene rendered with different values for the </span>**Sample size**<span style="color: #000000"> parameter. All other values are the same.</span>

<span style="color: #000000">Note the difference in the noise level between the samples.</span>



> Macro (anchor)



---


### **Example: The Scale Parameter**

** **

The **World Scale** option determines whether the **Sample Size** and **Filter Size** parameters are in screen space, or world space.

In the table below the World Scale checkbox is not enabled, meaning that the Screen scale is used, and the scene was rendered with different image and world sizes. The **Sample Size** was constant (the default value of *0.02*) for all images.

As you can see, we always get the same number of light cache samples for all cases, regardless of resolution or scene size - in fact, when scaled to the same size, the images look identical. This is why the Screen Scale is applicable to a large variety of scenes.



In the table below, the World Scale mode was used. Again, the scene is rendered at three different resolutions and scales, but with the same light cache parameters. The sample size was set to be 1/6th of the sphere radius in the scene at normal scale.

You can notice that the number of samples again does not depend on the image resolution, but it does depend on the scene size.  
Also notice how the samples near the camera appear larger because of the perspective - in difference from the Screen scale mode which compensates for this effect and tries to make the samples with more or less equal size on the image.


** **


## **Notes**

---

- Do not apply perfectly white or very close to white materials to a majority of the objects in the scene, as this causes excessive render times. This is because the amount of reflected light in the scene decreases very gradually and the light cache has to trace longer paths. Also avoid materials that have one of their RGB components set to maximum (255) or above.