Assume you have a colour mix node that you are using to determine the roughness value of a Glossy BSDF. Is there any way to actually see the roughness value? Is there a way to see set values of nodes in general, if they are not set "in place"?

  • $\begingroup$ AFAIK you can't :( all you can do is preview the value (0<value<1) with an emission shader, but nothing accurate... $\endgroup$
    – Bithur
    Mar 15, 2015 at 1:26
  • $\begingroup$ I like to plug values into an emission shader to visualize them in the viewport. if I understand your question correctly I think that is as close as you can get. $\endgroup$
    – PGmath
    Mar 15, 2015 at 1:55

1 Answer 1


Plainly as a number, no. Approximately, yes.

You can plug anything into the color input of an emission node and plug that into the surface material output. This will let you visualize the values across the mesh in the viewport with rendered viewport mode.

There is a handy addon written by Greg Zaal, called node wrangler, which (along with a billion other useful things) will do this automatically by Ctrl + Shift + LMB (left clicking) on a node.

To make numerical values easier to distinguish you can plug the value into a color ramp node first, then you can create a colorful gradient in the color ramp which will make it easier to see the value in the viewport.

  • $\begingroup$ It would be good to have some kind of "probe" node to display values. The values exist and must be assigned somewhere and I bet a python script can do this. $\endgroup$
    – Pat Hertel
    Mar 16, 2015 at 3:04
  • $\begingroup$ @PatHertel Yes it would, but the problem is that often the value of a property will vary at each point on the mesh, which isn't really feasible to display in any way other than as a color. $\endgroup$
    – PGmath
    Mar 16, 2015 at 14:22
  • $\begingroup$ @PatHertel Holding the left mouse button over whatever part of the mesh you're interested in in the rendered image shows you the RGBA values (among other things). This could be problematic if the values you want are above 1.0 or below 0.0 though - I never tried if Blender retains such "impossible" colours. $\endgroup$ Mar 16, 2015 at 16:51
  • $\begingroup$ @MartinSojka Blender will keep RGB values greater than 1, they are in fact quite useful in the compositor. $\endgroup$
    – PGmath
    Mar 16, 2015 at 18:58
  • $\begingroup$ @PGmath Yeah, I just checked with a quick node setup (Geometry's Position output to Emission's Color input) - Blender also happily keeps and shows you negative RGB values in the rendered image (... or any image, for that matter). $\endgroup$ Mar 18, 2015 at 8:48

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