Lightmap Tutorial


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Radiosity Lightmap generation with Blender (Part 1/2)

This tutorial has been created with Blender 2.46 but it should be possibel with 2.45 too.
Note: Blenders UV Face mode has been removed since 2.46 and is now part of the edit mode.

The first thing you need is a scene. Here's mine:

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You can copy it or create your own but it should not be too complicated now.
As you see it is made of separate objects which will share one lightmap.

At first select the objects that will share one lightmap and enter UV Face/Edit mode (One of the objects has to be active).
Select all faces and push the 'U' button. you will see a menu choose Lightmap UV Pack.

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From the next menu disable Active Object and Selected Faces and enable Share Tex Space, New UV Layer and New Image. Select the image size you'd like for the lightmap. Also change the margin value to a higher value than 0.100, especially when you use a small image size. OK

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Now you can check the unwrapped faces by selecting the objects one-by-one and enter UV Face/Edit mode:

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Now select the ground and do the same as before to create a lightmap for it. But this time don't disable anything because it's not necessary here.
Enable only New UV Layer ( don't enable it if you unwrap it the second time to correct the UVMap i.e with different margin value).Somehow the New Image won't have any effect anymore. Because of that you will have to create a new image on your own. With all faces still selected go to the Image Editor and create a new Image (3). A size of 128x128 should be enough. Exit UV Face/Edit mode.

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The unwrapping is finished so far. The next thing is to create some light sources. Usual lamps do not work with radiosity you need a mesh with an emitting material. Select the latern and then select the faces where the light should come from. In the Edit buttons create a new material (2) and assign it.

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Now go to the Material buttons and change Emit to a non-zero value. You can change the color as well.

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Switch to radiosity buttons, select all meshes with 'A' or the right mouse button then push Collect Meshes (1) and Go (2).
The calculation will start. When it's finished decide if the result is ok. If not Free Radio Data (4) and change the Emit value otherwise push the Add new Meshes (3) button and then Free Radio Data (4). (Select Gour to get smooth schadow results).

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The result of radiosity:
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Lightmap Tutorial Part 2

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