# Bump map question

I guess this applies to different mapping, but I’m doing a bump map atm

So I have a grey image as my bump map, and when I scribble dark grey on it, the bumping interprets that as where it should deepen, when I scribble white or light grey on it, the bumping is outwards… as I want it

I am wondering what Blender does to recognize the grey as the neutral colour? Meaning the colour that it doesn’t bump either way… Is it because it’s the most common colour or something?

I thought maybe it looks at the brightest colour and the darkest and uses the average of those colours as the neutral colour, but when I have the primary colour as black and scribble white, it takes the black as the neutral colour and acknowledges the white colour as what I want to bump.

Does anyone know?
Thanks

Try a mid grey, Red=0.5, Green=0.5, Blue=0.5

usually the backgroug should be in the middle like R=G=B0.5

see this site here

but alsp check out noob to pro site
which has a good description for bump normal and displacement maps

happy 2.5

Well… what else did you expect? You have a float value from 0-1 from your image… but you want bumps to have a direction so a value of -1 is as deep as you can go into the surtface and 1 is as high above teh surface as you get… 0 would be in the middle…

so how do you map a value from range 0-1 to be range -1 to +1?

You subtract 0.5 and then multiply by 2

(texture value -0.5)*2

Mathmatically a value of 0.5 (mid grey) will work out at zero… (no bump)

then you multiply by the “normal” slider in the “map to” tab to scale how high maximum an minimum depth are…