Node Editor - invert
- Thread starter wal3d
- Start date
Rene66
0
the SUBTRACT node (in the Math category) will do the trick.
• Create a new material - in the Node editor, create a new IMAGE & SUBTRACT node.
• Set the "A" value in the SUBTRACT node to "1.0"
• Plug in the "Color" from your IMAGE node (that has the height map loaded) into the "B" value of the SUBTRACT node.
• Plug in the the "Val" of the SUBTRACT node into the "Bumpmap" of the MATERIAL node.
done
• Create a new material - in the Node editor, create a new IMAGE & SUBTRACT node.
• Set the "A" value in the SUBTRACT node to "1.0"
• Plug in the "Color" from your IMAGE node (that has the height map loaded) into the "B" value of the SUBTRACT node.
• Plug in the the "Val" of the SUBTRACT node into the "Bumpmap" of the MATERIAL node.
done
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Rene66
0
We learn by playing around with things - and reading posts on the forum. This inverse trick I learned from a post by Podperson.
With the nodes, it's all math I have discovered and Colors are like percentages: 0.0 = 0%, 0.6 = 60% and 1.0 = 100% etc.. In this case we're dealing with a bump map which is grey scale 0.0=black & 1.0=white.
If a pixel on your bumpmap is 67% grey and you need the inverse (33%) - using the SUBTRACT node gets you there.
(A)1.0 - (B) 0.67 = .33 (33%grey)
Hope that helps clarify what's happening with this "trick" - Continuing playing
With the nodes, it's all math I have discovered and Colors are like percentages: 0.0 = 0%, 0.6 = 60% and 1.0 = 100% etc.. In this case we're dealing with a bump map which is grey scale 0.0=black & 1.0=white.
If a pixel on your bumpmap is 67% grey and you need the inverse (33%) - using the SUBTRACT node gets you there.
(A)1.0 - (B) 0.67 = .33 (33%grey)
Hope that helps clarify what's happening with this "trick" - Continuing playing
A color image map can be inverted by subtracting from 1.0 in x y and z (which act as R G and B).
You can also brighten, darken, increase contrast, and -- if you're clever -- apply gamma correction. If you want to apply "curves" you can create a black-to-white gradient in Photoshop, apply the curve to that gradient, and then use a slice of that image as a "look up table" (if you're interested, I can post more details on this).
It's all arithmetic or a little algebra.
E.g. brighten an image, use an add node to add a small amount (e.g. 0.1, 0.1, 0.1) or add a color (e.g. light gray). To manipulate contrast, subtract 0.5, 0.5, 0.5, and then multiply by a number (1.0 has no effect; 2.0 increases contrast, 0.5 decreases contrast), and then add back 0.5, 0.5, 0.5.
(You'd be shocked at how simple most of the things Photoshop does are at a pixel level — my favorite discovery from a paper on this stuff was that sharpening is done by blurring an image and then subtracting that image from the original (!). Think of it as Sharpened Pixel = Original Pixel x ( 1 + epsilon ) – Blurred Pixel x epsilon. If you use a matrix blur you get crude sharpening, if you use guassian blur you get unsharp mask.)
You can also brighten, darken, increase contrast, and -- if you're clever -- apply gamma correction. If you want to apply "curves" you can create a black-to-white gradient in Photoshop, apply the curve to that gradient, and then use a slice of that image as a "look up table" (if you're interested, I can post more details on this).
It's all arithmetic or a little algebra.
E.g. brighten an image, use an add node to add a small amount (e.g. 0.1, 0.1, 0.1) or add a color (e.g. light gray). To manipulate contrast, subtract 0.5, 0.5, 0.5, and then multiply by a number (1.0 has no effect; 2.0 increases contrast, 0.5 decreases contrast), and then add back 0.5, 0.5, 0.5.
(You'd be shocked at how simple most of the things Photoshop does are at a pixel level — my favorite discovery from a paper on this stuff was that sharpening is done by blurring an image and then subtracting that image from the original (!). Think of it as Sharpened Pixel = Original Pixel x ( 1 + epsilon ) – Blurred Pixel x epsilon. If you use a matrix blur you get crude sharpening, if you use guassian blur you get unsharp mask.)
So you´re saying you can invert a colored map with the subtraction-node? All I see is inverted brightness not inverted RGB-values here.
I´m used to use another approach to invert colors. Just curious.
Cheers
Frank
I´m used to use another approach to invert colors. Just curious.
Cheers
Frank
Cool! :icon_thumbup:
Cheers
Frank
Cheers
Frank
Rene66
0
Downloaded these samples - Very Cool - Thank you for the insights!!!
Hi everyone
Podperson or anyone.
Are there math node equivelents to blending modes such as 'screen' & 'lighten', 'darken', 'overlay', 'softlight' etc. that you find in image editing apps?
Thanks, Shift Studio.
Podperson or anyone.
Are there math node equivelents to blending modes such as 'screen' & 'lighten', 'darken', 'overlay', 'softlight' etc. that you find in image editing apps?
Thanks, Shift Studio.