From the Blender Docs:


Strength of the bump mapping effect, interpolating between no bump mapping and full bump mapping

The idea of mixing together two effects isn't new to me, it makes sense, when I say, mix a blue diffuse shader with a red diffuse shader and plug it into the Material Output, the color would be a 50% mix of red and 50% of blue, getting me a new color. I can use the Fac input to precisely control the mixing to my liking

From what I know about bump maps, we calculate the derivatives of a specific pixel on a bump map when it's mapped to a mesh to find exactly where the new, perturbed normal on a part of the mesh should point

What does it mean to interpolate/mix between no and full bump mapping logically, however? In mixing between two diffuse colors, we mix the colors. But what exactly is mixed when we interpolate/mix between full and no bump mapping?

If a specific pixel on the bump-map perturbs the normal say to the right at 100% strength, at 50% strength would it only say, perturb it half as much to the right?

How does it work with the Distance input? If the distance = 1, would 50% strength leave us with a perturbed normal that is at a distance of 0.5 ,and distance of 1 at 100% strength?

  • $\begingroup$ Good question. What exactly is the difference between increasing tilt of the normal, and adjusting the height from which it is calculated? $\endgroup$
    – Robin Betts
    Sep 1, 2021 at 6:55
  • $\begingroup$ @RobinBetts Sorry I am not sure of the answer. Also what do you exactly mean by 'height from which it's calculated'> $\endgroup$
    – Hash
    Sep 1, 2021 at 7:15
  • 1
    $\begingroup$ I'm just saying I would like to know the answer to your Q, too. A Bump node converts height information to normals, approximating d_height / d_tangent_x, and d_height / d_tangent_y. Often using a Sobel filter.The 'Height' field scales the height input. The 'Strength' field mixes the resulting perturbed normal with straight-up Z, I think. (Could be wrong...) But I can't work out the mathematical difference between these settings.. (I have to get the pencil and paper out :) ) $\endgroup$
    – Robin Betts
    Sep 1, 2021 at 7:51
  • $\begingroup$ Does this answer your question? Understanding the bump node $\endgroup$ Sep 1, 2021 at 14:07


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