Lighting plug in

Current version: 0.37 beta (see notes below)
Last changed: 17-Sep-1996
Upcoming changes/bugfixes? Yes
Tested platforms: IRIX 5.3, SunOS 5.4 (Solaris 2.4), SunOS 4.1.3
GIMP API version: 0.54.1 (Tue Feb 13 10:29:00)

The plug-in source code is available [here]


Table of contents


This plug-in enables you to add various types of lighting effects to your (RGB) image. Optionally you can specify a refractive, reflective layer on top of the image to achive special effects (glass, water, slime, distortion etc.) You can choose among three light models:

You can choose to apply lighting on image only, layer only, both or none. Additionally you can specify two kinds of mapping to apply to your image or layer. One is the traditional "wavy" mapping which makes a -uhm- wavy mapping. The other is "bump-mapping", where you specify another image as source for your bumps. Also, for the refractive layer, you can specify seperate mappings for index of refraction and layer thickness (more on this later).

Light position and direction

In this section I will explain how to set the position and direction of the light source, and try to suggest some useful settings. All coordinates are relative to the image mapping, which is the unit square [(0,0)..(1,1)] (upper left, lower right).

Directional light

Directional light is non-local light such as the Sun, i.e. light-sources "infinitely" far away. A few common direction settings; [0.0,0.0,1.0] (light directly from above), [-1.0,-1.0,1.0] (light from above, upper left corner), [1.0,1.0,1.0] (light from above, lower right corner). Well, you get the idea :) The default settings for this light-type is [-0.5,-0.5,-1.0].

Point light

Point light is local light-sources, like a free-hanging light bulb of no size. Positioning it at (0.5,0.5,+Z) places it above the center of the picture. The Z value should be positive, although I have not (yet) restricted you from entering negative values; you could get pretty odd results by doing it, though. Default position is [0.5,0.5,2.0].

Spot light

Spot light is like a, er, well.. spot light :) A directional point light, or something :) In addition to a position (P), you specify a direction (D) and a angle (A), which controls the light fall-off effect. A spot light defines a cone with its apex at P, its principal axis along D, and its range controlled by A.

Usage examples

Main dialog

Refraction settings dialog

Material settings dialog

This dialog lets you adjust the material properties of your image or layer. The values set here are critical for how the result will look, so make sure you experiment a bit with them and understand what they do.

Wave settings dialog

Map from image dialog

From this dialog you can specify from what image you want to map, how to scale the data from the image and how to map the scaled data to fit your needs. Here's an explanation of what the various fields do:

Dialog screenshots

  1. Main dialog
  2. Refraction dialog
  3. Material dialog
  4. Wave dialog
  5. Map dialog

Last changed 17-Sep-1996 by Tom Bech (