Iteration
These fields control behavior specific to the actual iteration process. They differ from other fields in that they will likely have different values between the interactive renderer, and the Final Render dialog.
For example, quality should be kept fairly low and supersample set to 1 for a responsive UI, however when doing the final render, you will want to increase the quality and set the supsersample to at least two.
Sub batch size
Iteration is broken up into chunks, and after each chunk the point trajectory is set to a random number before beginning the next chunk.
For images which need a tighter, more concentrated look, increase this value because larger values reset the trajectory less often.
In practice, this has no noticeable effect on most images and therefore will almost never need to be adjusted.
Default: 10,240
Fuse count
When starting each sub batch, the first fuse count iterations are not plotted on the histogram. This allows the image some time to converge before plotting to reduce noise.
For images which need a tighter, more concentrated look, increase this value because larger values allow greater convergence before plotting.
In practice, this has no noticeable effect on most images and therefore will almost never need to be adjusted. However it has very noticeable affects on others.
Default: 15
Rand range
When starting each sub batch, the first point value is chosen randomly.
When a bad point is computed, a new point is also chosen randomly.
This field allows you to specify the range in the x and y dimensions that the new point is chosen from in both cases.
For example, the default value of 1 means random points will have an x coordinate between -1 and 1, and a y coordinate between -1 and 1.
In practice, this has no noticeable effect on most images and therefore will almost never need to be adjusted. However it has a very noticeable effect on others.
Default: 1
Quality
The number of iterations per pixel in the final output image. Keep this value low for a responsive UI while editing, then increase it when using the Final Render dialog.
If this value is increased while a render is in progress, the updated value will be used once it finishes and it will pick up rendering where it left off.
This allows successive quality increases without restarting the render.
One way to increase the quality in this manner is to just type another digit in the field.
Decreases in quality will restart the process from the beginning.
Default:
CPU: 10
GPU: 30 * number of devices in use
Supersample
The value to multiply the dimensions of the histogram and density filter buffer by to help eliminate jagged lines. During interactive editing, it should always be 1, and should only be increased when preparing for a final render. Values greater than one will significantly impact performance and will increase memory usage.
While a value of 2 offers some visual improvement, values greater than 2 usually don’t offer noticeable improvement.
Default: 1
Range: 1 – 4