Light cache examples

Example 1: The Subdivs parameter

Example 2: The Sample size parameter

Example 3: The Scale parameter

Example 1: The Subdivs parameter

The Subdivs parameter controls the number of rays that are shot into the scene, and the "noise" quality of the light cache samples.

 

Here is a scene rendered with different settings for the Subdivs parameter, all other settings are the same.

• As we add more samples, the noise is reduced, but the render times increase. When the Subdivs parameter is increased twice, the light cache takes approximately 4 times as long to calculate.

 

Subdivs = 500	Subdivs = 1000	Subdivs = 2000

 

Example 2: The Sample size parameter

The Sample size 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.

 

Here is a scene rendered with different values for the Sample size parameter. All other values are the same.

• Note the light leak from the wall on the right in the last image - this is because samples from the other side of the wall are quite large (because of the Screen Scale) and end up being used on the side facing the camera (compare this with the World Scale in Example 3).
• Note the difference in the noise level between the samples.

 

Sample size = 0.01	Sample size = 0.02	Sample size = 0.04

 

Example 3: The Scale parameter

The Scale parameter determines whether the Sample size and Filter size parameters are in screen space, or world space.

 

In the table below, the Screen scale was used, and the scene was rendered with different image and world sizes. The Sample size was constant for all images - the default 0.02.

• 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 the large variety of scenes.

 

	Scene scaled down to 50%	Normal scene	Scene scaled up to 200%
Resolution 250x300
Resolution 500x600
Resolution 1000x1200

 

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 1/5th 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.
• Another thing to note is that we don't get light leaks (compare with Example 2), even when the samples are relatively large - this is because the World Scale forces a uniform sample size on both sides of the right wall.

 

	Scene scaled down to 50%	Normal scene	Scene scaled up to 200%
Resolution 250x300
Resolution 500x600
Resolution 1000x1200