[Award Winner] Using the mosaic filter to make towns in Gimp

[torstan]

Now we'll go back to that colour layer we left alone. First of all, we want to get rid of all the blocks of colour that represent houses that we no longer need.
1. Make sure your black and white mosaic layer is selected.
2. Select all (ctrl-a).
3. Copy (ctrl-c)
4. Select your colour layer.
5. Right click the colour layer in the layers dialogue and select Add Layer Mask...
6. Click okay in the dialogue
7. Select the layer mask in the layers dialogue.
8. Paste (ctrl-v) and anchor the pasted layer to the layer mask (click the little anchor at the bottom of layers dialogue).

Now the layer mask is the wrong way round at the moment - it is masking out the buildings and only revealing the white between. With the layer mask selected, go to Colours->Invert. You'll now have the mask the right way round. If you move the colours layer to the top of your layer stack you should now see something like this:



This is all very well, but the houses are just flat blocks of colour at the moment. We want to give them some substance. To do this, take the following steps.
1. Duplicate the black and white mosaic building mask layer and rename it something like "Building Bump Map"
2. Go to Colours->Invert to make the streets black and the buildings white. Remember, bump mapping takes white points to be the highest and black points to be the lowest, so we want the streets to be the lowest point.
3. Change to the Select by Colour Tool with threshold set to zero, and click on one of the white buildings to select all the buildings.

You should now have something that looks like this (note that I've turned off the visibility of the other layers so that I can see what I'm doing):



4. Switch to the gradient tool.
5. Select the Shaped Angular option in the Shape drop down.
6. Check the switch direction checkbox beside the Gradient: drop down
7. Click and drag inside one of your selected buildings to fill all of them with a shaped gradient.
8. Edit->Select None (ctrl-shift-a) to see your handiwork.

It should now look something like this:



This is now ready for use as a bump map.

9. Turn off the visibility of this layer and select your Colours layer again.
10. Right click the layer in the layers dialogue->Apply Layer Mask
11. Go to Filters->Map->Bump Map...
12. In the Bump Map dialogue make sure that your Building Bump Map layer is selected as the bump map.
13. Play with the Depth slider until the preview looks good.

Here are the settings I used:



14. Now click okay and you should have something like this:



In the next section we'll look at putting in a background and some finishing touches.