Render Settings - RT - Basic

Progressive Passes

Controls the maximum number of passes that Progressive rendering mode can reach and therefore controls the maximum achievable visual quality of Progressive mode. The higher the number of Progressive Passes the higher the render quality and the less visual noise, default is 1024 passes.

Since Progressive mode can be used in either Interactive Rendering or Final Rendering the behavior of this setting differs depending on the rendering mode and the situation.

• Progressive Passes with Production Interactive and RT Rendering - In Interactive Rendering the Progressive render will only reach the maximum number of Progressive Passes if given the necessary amount of time between scene edits and changes. 
  • For example: If a scene edit takes place before the maximum number of Progressive Passes is reached then a new updated Progressive render will be started and again begin to build back up to the maximum number of Progressive Passes.

• Progressive Passes with Production Final Rendering - In Final Rendering the Progressive render will always reach the maximum number of Progressive passes before moving on to the next frame, no more and no fewer.
  • For example: If your maximum number of Progressive Passes is set to 64 then each frame will be rendered for as long as it takes to reach the 64th pass. Once the 64th pass is reached, Redshift will move onto the next frame and then start the process over for each frame until the entire batch is finished.

 

Denoising

The Denoising checkbox allows you to quickly toggle denoising on and off. Denoising allows you to easily render images at a reduced baseline quality (lower sample counts) and increased speed at the expense of some potential accuracy. Denoising can only do so much and a balance must be struck between Bucket Quality and the denoiser engine of choice in order to find what works best for your project.

Global Illumination

The Global Illumination checkbox lets you quickly toggle bounced indirect lighting on and off. For the most realistic lighting Global Illumination should be left enabled but it will increase render times. For more information please see  this page.

In the example images below notice how the bounce lighting from the floor and wall next to the lantern is realistically filled in when Global Illumination is enabled.

Combined Depth

Depth parameters control how many times a ray of its individual type can interact with objects in a scene until it is terminated.

The Combined Depth parameter specifies the maximum number of times any individual ray can be used for global illumination, reflection, transmission / refraction, or volume scattering. Even if the depth values for an individual ray type is higher than the Combined Depth the resulting render will still be capped at the Combined Depth value. 

Separating the controls like this provides more flexibility, allowing individual effects to be rendered with increased depth when needed but restricting unnecessarily high render times. For example, let's say that reflection and refraction are both set to a value of 4 and combined is set to 6. If a ray had already been reflected 4 times, then it could only be refracted 2 more times because the combined trace depth is 6.

Global Illumination Depth

The Global Illumination Depth parameter sets an individual cap on how many times an indirect lighting ray can bounce. Increase this parameter for interior scenes where many indirect bounces are required for realistic lighting.

Reflection Depth

The Reflection Depth parameter sets an individual cap on how many times a reflection ray can bounce.

Refraction Depth

The Refraction Depth parameter sets an individual cap on how many times a refraction ray can bounce or pass through objects.

 

Transparency Depth

The Transparency Depth parameter sets an individual cap on how many times a transparency ray can pass straight through objects. Transparency is utilized for things like Opacity in the Redshift Material to go much deeper than complex refractions and render much faster than refractions.

The test scene below was modified specifically to demonstrate the impact of the depth settings by putting 8 panes of glass in a row in front of the camera. Each pane of glass has actual thickness so for a ray to fully pass through one it requires a trace depth of at least 2, since there are 8 panes of glass a minimum trace depth of 16 is required to see through all 8 panes. See below that the glass on the lantern is not even visible until the refraction trace depth is high enough to get through all 8 panes of glass and the lantern glass itself. These same limitations are imposed on each ray type by their individual caps as demonstrated in the last example where the Global Illumination and Reflection Depths are reduced well below the Combined Depth resulting in the loss of most of the reflections and global illumination.