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12.2.  Bump Map

12.2.1.  Overview

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

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

12.2.2.  Options

Figure 11.154.  Bump Map” filter options

Bump Map filter options
Bump Map

This drop-down list allows you to select the image that will be used as a map for bumpmapping. 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 heigth is a direct function of luminosity.

  • Sinusoidal: bump heigth is a sinusoidal function of luminosity.

  • Spheric: bump heigth is a spheric function of luminosity.

Compensate for darkening

Bumpmapping tends to darken image. You can compensate this darkening by checking this option.

Invert Bumpmap

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

Tile bumpmap

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

Azimut: This is about lighting according to the points of the compass (0 - 360). If you suppose South is at the top of your image, then East (0°) is on the left. Increasing value goes counter-clockwise.

Elevation

Elevation: That's heighth from horizon (0°), in principle up to zenith (90°), but here up to the opposite horizon (180°).

Depth

With this slider, you can vary bump heigth and hollow depth. The higher the value, the higher the difference between both. Values vary from 0 to 100.

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 bumpmapping. With this slider, you can reduce hollows as if sea level was raising. This hollows will disapear when sea level value reaches 255. If the Invert Bumpmap 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.

An example

Figure 11.155.  From left to right: original image, bump map, bumpmapped image

From left to right: original image, bump map, bumpmapped image

 
 
  Published under the terms of the GNU General Public License Design by Interspire