BumpMapping Level II

I think there is a lot of potential in bumpmapping that is overlooked and today im going to show you how you can add some complexity to the basic technique.

The key element of bumpmapping is blurring and as all my gimp-scientist-padawans know, blur means you can shape it with an alpha-curve ! :)

01. So for our exercise, i set up a square canvas 600x600px in scientific green, with guides at 50% horizontically and vertically.

02. Create a gradient on a new tansparent layer, from white to transparent, radial shape, with adaptive supersampling ticked

03. Shape the gradient with an alpha-curve, first in a rough form and then refine.

04. Create a new layer on top of your background and below the gradient in a 50% grey (#808080).....

turn off the gradient layer !

05. With the grey layer active, bumpmap the gradient layer and you get this "speaker" shape:

06. Next create a circular selection from the middle, save it to a channel, invert and delete from the grey layer....

07. deselect then blur the channel by 5px.

08. Activate the speaker layer and bumpmap it with the channel.
Of course i could have done this as before by filling the selection with white on a transparent layer, but there is no difference. You can bumpmap with layers but also with channels.
Sometimes using a channel is more convenient.

Now some decoration:

01. Create a new grey layer on top of the BG.

02. Create a circular selection from the middle and make it bigger than the speaker and delete from the grey layer.

03. Create a rectangular selection from the middle and delete.

04. Repeat until you get a nice decorative shape, that you like.

I also want rounded edges, so i blur (12px) and then tweak with an alpha-curve.

Alpha select your deco and save it to a channel for future use.

05. Duplicate decor layer, put it on top, lock alpha channel, drag white over it, unlock

06. Blur white layer (8px), then turn off the eye

07. Activate grey decor layer and bumpmap

08. For more decoration, call up the selection from the saved channel and shrink (i used 26),

then fill on a new transparent layer with grey.

09. Deselect – for rounded edges repeat blurring and an alpha-curve

10. Duplicate, put on top, lock alpha channel, drag white, unlock and blur (12px) as above for the bumpmap.

11. For a little variation we are giving the bump map a contour. Heres a reminder from a previous tutorial what contours can look like:

I used this one (basically the 'Ring Contour' with some customisation):

Here is a little trick: giving a bumpmap a contour and then applying the bumpmap often results in jaggy edges....

what can help is blurring the bumpmap again - 3-5px seem like good values....

then bumpmap !

12. You can repeat this forever, with texture, patterns, structures. Be creative !

For another example lets give text a contour:

Type your text.

For the bumpmap: duplicate layer, lock alpha channel, drag white over it, unlock, then blur (i used 10), shape contour, put on top.

See how you get all ugly jaggy edges when you bump map it like it is:

But blur the contoured bumpmap again by 5px and it looks nice and smooth like this !

To finalize the piece i mapped a gradient on the text, played with value curves and applied anisotropic smoothing (a bit like in my Kitsch Chrome Tutorial).

On top of that G'MIC 'Light Glow'.

Added a dropshadow that i displaced with the speaker bumpmap.

The blue light effect is just radial motionblur

That concludes this tutorial, hope you like it !

XCF Download


Update 2019

Noticed some interest in this thread so i had another look at the existing xcf file and tried to give it an update. Especially getting rid of the sterile grey plastic look.

First step was to bumpmap the decorative elements with 10% noise to give them a grainy surface, so they are more in line with the center element..

Then i added several textures with Layermodes, some of them very subtle, to make everything look more varied.

I used only Gimp's native patterns, but processed with the Resynthesizer plug-in. 

You can introduce some interesting tonal variation by simply putting a 'Difference Clouds' layer in 'Hard Light' or 'Soft Light' Mode on top (with reduced Opacity).

Colourised everything and then fixed the contrast with Curves.

Finally added a bit of yellow to the texturing with a luminosity mask.