Percentage of Lighting Impact: Unlocking New Possibilities for Artistic Creation

I used to use this exact feature in vRay back when I was a Maya Vray user. Vray would only allow this granular multiplication or subtraction for diffuse/glossy/volume. It would be interesting to see if it is also possible for transmission.

I suppose it all depends on how cycles handles the relationship between light attributes and materials. It would be cool if it were as simple as including a float/percentage attribute connected math multiplication or subtraction operation that is global to all materials in the scene per light. I believe this is how vRay handles it somehow.

For me this feature was best used if wanting to pump only the glossy contribution of a light whilst keeping the diffuse contribution quite subtle.

It can be argued that this feature can encourage artists to create non physically plausible scene set-ups. Sometimes it can be necessary/useful though and avoid the need to render an extra pass to achieve a similar effect.

These sort of features though, should be used with caution and consciously adjusted knowing that it is a work around/convenience vs needing to render additional passes, very similar to light linking.

A photographer on a set has to shoot multiple scenarios and assemble in post to get the same effect vs ray isolation and light linking. In 3D, we can avoid this with granular controls not available in the physical world at the expense of more scene variables to track and control. It just needs to be used with caution whilst always considering real world lighting scenarios if the end result is photo realism. Breaking physically plausible setups is okay so long as used the correct way.