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The pic may explain better.

Cycles. . . . . .

I don't want smaller bumps that are still basically bubble-shaped... I could get that by just decreasing the strength of the normal in my normal map node.

What I want is for the bumps to come up from the surface at a certain strength, and then get abruptly clipped/clamped so that they're limited in how far they rise above the surface.

I thought of trying to use a color ramp or contrast node to limit the brightest and darkest parts of the image, to clip it that way, but it doesn't work. The normal map is one of those proper purple-colored things and not easily edited in photoshop. I tried playing with height and distance settings in a bump map, but that just seems to make shorter bubbles, not "cropped" bubbles.

normal clamping

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    $\begingroup$ Please specify Cycles Render or Blender Render. $\endgroup$
    – atomicbezierslinger
    Commented Jul 4, 2018 at 9:06
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    $\begingroup$ Cycles. . . . . . $\endgroup$
    – CreeDorofl
    Commented Jul 4, 2018 at 14:09

1 Answer 1

Reset to default
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Node Setup

Pass the bump height through a Math > Minimum node. Set the empty value to your desired clamp height.

0.5 Clip

0.5 Clip

0.75 Clip

0.75 Clip

Clip Off

No Clipping

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    $\begingroup$ ...and set the empty input of the math node to the value that will clamp the top. The 'Min' operation will output the minimum value between the height map and the other value, so anything higher than in the height map will revert to the other socket value. $\endgroup$
    – Secrop
    Commented Jul 4, 2018 at 6:45
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    $\begingroup$ OK, it sounds right... but I'm struggling to make it work. It may help to show what my node setup is. i.imgur.com/xGrXOuI.jpg It's one of the pre-built ones from blenderguru / poliigon. It has both a displacement and a normal map. It's confusing but I think the author of the setup wanted to make it so you can use both displacement + normals. So he has a bump node which accepts height input from a displacement map, and normal input from normal map. This bump node outputs to the shader. If I cut the displacement out, it doesn't change visually. So the normal is doing the work. $\endgroup$
    – CreeDorofl
    Commented Jul 4, 2018 at 14:32
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    $\begingroup$ Part 2: So I've tried putting the minimum node everywhere... between displacement and bump node (height input)... between normal and bump node... between bump and shader... none of them seem to work or produce odd artifacts. I test different values too like .1, 1, 10 to ensure the effect isn't just too subtle to see. $\endgroup$
    – CreeDorofl
    Commented Jul 4, 2018 at 14:34
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    $\begingroup$ ok, I finally see how it works. The normal map won't be affected by "min" the same way a displacement map would be... the normal map has all this extra information and is more complex than just "brighter = higher, darker = lower". But a displacement map IS that simple, just a grayscale image. The min node just changes the maximum amount of white/lightness in that image so the bumps can't go past a certain height. So I disabled the normal map, and did this: Grayscale image --> mininum math node --> height input of bump node --> normal input of shader. $\endgroup$
    – CreeDorofl
    Commented Jul 4, 2018 at 16:03
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    $\begingroup$ And if this confuses anyone else, the min node must very very close to 0.5 (in my case). If I make it 0.45, the bumps disappear completely and it's like the node isn't working. If I make it 0.6, the bumps are almost 100% height. To really get the look I wanted I needed exactly 0.485. I also had 0.3 strength on the bumps because at 1, their apparent height doesn't look any different, but their shadows look way too dark and black. $\endgroup$
    – CreeDorofl
    Commented Jul 4, 2018 at 16:06

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