Bring back and improve the Square Samples option

The "Square samples" option has been removed from Cycles, but I'd like to have it back.

For those new to the concept, the "Square samples" option isn't as much a render option as it is a UI preference setting. Under the hood, it simply tells Blender to multiply the specified sample value in the Max and Min Samples fields by itself, to get the total number of samples to use for the final render.

Here's why someone might prefer this:

• The perceived render quality aligns more closely to the number you type in . Sample counts have extremely diminishing returns. At high values, you need to make exponentially larger adjustments to get the same difference in quality. Using squared samples makes this relationship more or less linear. If you want to double the render quality, you double the number of (squared) samples.

• Prevents needlessly high values . Squared samples means you don't have to deal with numbers in the tens of thousands, and don't need to make adjustments in the thousands. Very large numbers are harder to work with, you need to start counting zeroes and keep many more digits in mind. And dragging on the input field to make adjustments becomes very impractical.

• It's more industry compatible. Many, if not most, other render engines use squared sample inputs. Having this option back would make Blender even more familiar to industry professionals switching between render engines, if just a little bit. Blender is nearly alone in the industry in using straight samples instead of squared samples (or sampling subdivisions as it's usually called)

The rationale for the removal of this feature was that it can confuse new users who suddenly find themselves with extremely long render times after enabling it without knowing what it does. This could be mitigated somewhat with a couple of improvements:

• Display the true sample count as text next to the input field when the feature is enabled
• Rename the option to "Squared samples" to make the name more descriptive
• Hide it away under the advanced tab, where users should know to go at their own peril

I think it's reasonable to try to make the feature less mysterious rather than removing it for everyone who actually do use it. Many useful features of Blender are confusing to new users. It feels like the actual usefulness of the feature might not have been considered when deciding to remove it.