12.2. Bump Map
| 12. Map Filters |

### 12.2. Bump Map

#### 12.2.1. Overview

Figure 16.236. “bump-map” example

On the left, the original image that we want to emboss: a solid blue. In the middle, the bump map : a grayscale image, where black pixels will emboss backwards and white pixels will emboss forwards. On the right, the bump-mapped image. The filter adds a shadow effect.

This filter creates a 3D effect by embossing an image (the card) and then mapping it to another image. Bump height depends on pixel luminosity and you can set light direction. See Emboss for more information about embossing. You can bump map any type of image, unlike the Emboss filter.

#### 12.2.2. Activate the filter

This filter is found in the image window menu under Filters → Map → Bump Map.

#### 12.2.3. Options

Figure 16.237. “Bump Map” filter options

Preview

  Parameter setting results are interactively displayed in preview. Scroll bars allow you to move around the image.

Bump Map

  This drop-down list allows you to select the image that will be used as a map for bump-mapping. This list contains images that are present on your screen when you launch the filter. Images opened after starting filter are not present in this list.

Map Type

  This option allows you to define the method that will be used when creating the map image:

  - Linear: bump height is a direct function of luminosity.

  - Sinusoidal: bump height is a sinusoidal function of luminosity.

  - Spheric: bump height is a spheric function of luminosity.

Compensate for darkening

  Bump-mapping tends to darken image. You can compensate this darkening by checking this option.

Invert bump-map

  Bright pixels default to bumps and dark pixels to hollows. You can invert this effect by checking this option.

Tile bump-map

  If you check this option, there will be no relief break if you use your image as a pattern for a web page: patterns will be placed side by side without any visible joins.

Azimut

  This is about lighting according to the points of the compass (0 - 360). East (0°) is on the left. Increasing value goes counter-clockwise.

Elevation

  That's height from horizon (0.50°), up to zenith (90°).

Depth

  With this slider, you can vary bump height and hollow depth. The higher the value, the higher the difference between both. Values vary from 1 to 65.

X/Y offsets

  With this slider, you can adjust the map image position compared with the image, horizontally (X) and/or vertically (Y).

Sea Level

  If your image has transparent areas, they will be treated like dark areas and will appear as hollows after bump-mapping. With this slider, you can reduce hollows as if sea level was raising. This hollows will disappear when sea level value reaches 255. If the Invert bump-map option is checked, transparent areas will be treated as bright areas, and then Sea Level slider will plane bumps down.

Ambient

  This slider controls the intensity of ambient light. With high values, shadows will fade and relief lessen.

12. Map Filters |  | 12.3. Displace