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Howto:Multi-channel lightmap: Difference between revisions
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Lightmaps on the other hand only work for a static scene, but since they can be computed offline with the help of raytracing software (which can run for hours if needed), secondary shadows and multiple reflections of light on bright surfaces are not an issue. In addition, at runtime a lightmap corresponds to just a texture lookup, i.e. is very performance-friendly. | Lightmaps on the other hand only work for a static scene, but since they can be computed offline with the help of raytracing software (which can run for hours if needed), secondary shadows and multiple reflections of light on bright surfaces are not an issue. In addition, at runtime a lightmap corresponds to just a texture lookup, i.e. is very performance-friendly. | ||
For many situations where a light on an airplane illuminates that airplane (both in interior and in exterior view), lightmaps thus are a useful technique. | For many situations where a light on an airplane illuminates that airplane (both in interior and in exterior view), lightmaps thus are a useful technique and can lead to graphically very impressive outcomes: | ||
[[File:Shuttle lightmap.jpg|800px|Example of a raytracer generated lightmap for the Space Shuttle cockpit]] | |||
FG supports both single channel maps (the rgb value of the lightmap encodes the full color of the light at that pixel) and multi-channel lightmaps. In these, each r,g,b and a of the lightmap texture specify intensity of the light, the color (which can then not vary across the lightspot) has to be supplied per channel as a parameter. | FG supports both single channel maps (the rgb value of the lightmap encodes the full color of the light at that pixel) and multi-channel lightmaps. In these, each r,g,b and a of the lightmap texture specify intensity of the light, the color (which can then not vary across the lightspot) has to be supplied per channel as a parameter. | ||
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The multi-channel lightmap effect can be extended relatively easy to allow for as many as 8 light sources. The SpaceShuttle was extended to use 8 lights in the cockpit. | The multi-channel lightmap effect can be extended relatively easy to allow for as many as 8 light sources. The SpaceShuttle was extended to use 8 lights in the cockpit. | ||
But because it is out of the scope of this tutorial I will just refer you to look at the following files to see how it is accomplished. | But because it is out of the scope of this tutorial I will just refer you to look at the following files to see how it is accomplished. | ||
Extending the multi-channel lightmap to allow for more lights should only be undertaken by experienced developers that are somewhat familiar with the XML effects wrapper and GLSL code. | Extending the multi-channel lightmap to allow for more lights should only be undertaken by experienced developers that are somewhat familiar with the XML effects wrapper and GLSL code as it requires to have shader code aircraft-side. | ||