Understanding Tracing Depth with Presto (MC)
What is Tracing Depth?
Tracing Depth is the most important parameter for Presto (MC) as it plays a significant role in the overall look of the scene and of course render times. The default value (5) is optimal for scenes with low complexity.
What is Diffuse Depth?
Diffuse Depth controls the amount of global illumination (GI) bounces inside a scene. When enabled, values control the light bounces in the scene. A value of 0 means that there will be no secondary bounces leaving only the direct lighting visible.
Note: When Diffuse Depth is disabled, Tracing Depth controls the number of secondary bounces.
What is Extended Tracing?
Extended Tracing makes it possible to increase the Tracing Depth for specific parts of a scene (e.g. transparent materials, tree leaves, etc) without the need of increasing the overall Tracing Depth that would result in higher render times.
Example using Tracing Depth
Image 1: Tracing Depth is set to 5 while Diffuse Depth and Extended Tracing are disabled. While the lighting in the scene is fine, transparent objects appear black due to the Tracing Depth having a low value.
Render Time: 4m03s
Image 2: To overcome the transparency issue, we raise the Tracing Depth to 20. This makes the transparent materials to render fine but light bounces have increased too, increasing this way the render time.
Render Time: 10m19s
Image 3: Tracing Depth has been set to the default value of 5 and Extended Tracing has been enabled using the default values (15 for all). In this way, the trasparent material will have a tracing depth value of 20 (5+15) while the light bounces remain at 5, reducing this way the render time.
Render Time: 7m52s
Example using Diffuse Depth
Image 4: Diffuse Depth set to 0. Only direct light is visible in the scene
Image 5-7: We gradually increase the Diffuse Depth to 1,3, and 5 accordingly. The light is now bouncing in the scene increasing this way the overall brightness.