This tutorial will guide you through some quick&easy steps necessary to setup a Global Illumination scene for a care-free compositing.

If your background picture is not an HDR image or in case you have an .avi file running you can use the good old (albeit only slightly modified) skydome for scene illumination and that's what we'll create first.

Step 1
In Modeler create a sphere,leave its resolution at their default values - just make sure that the size of the sphere goes well beyond your scene perimeter.

Since we are compositing,the Skydome horizon line will not be visible as such in your render but having a very distant horizon could help you with the camera angle matching and also it ensures that your scene elements will be well..."globally illuminated"

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Step 2
We need to eliminate the bottom half so in Polygon mode select all the polygons along -Y axis...

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Step 3
Go to Construct - Merge Polygons (Shift+Z) to collapse all of the selected polygons into a flat ground plane

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Step 4
In Point mode open Statistics panel ("w") and select all of the 0 polygon points (or you can simply Lasso them) and delete them all cos they are no longer of any use to you (space junk )

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Step 5
Now go back to Polygon mode and hide the ground plane (-) and then Cut the rest and paste it into Layer2

Press "q" and assign a new surface to the hemisphere ("skydome" or similar) and make it 100% Luminous and 0% Diffusive and set the colour to slightly off-white

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Step 6
Activate Layer1 too and unhide the ground polygon "" and flip both layers "f".
Save the model cos we're done modeling.

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* In case you wonder why we didnt make a simple flat box for the ground plane - the reason is that this way we have a perfect allignement with the dome so our ground does not extend beyond its area of illumination (it would produce a dark division band in the render) nor does it fall short of reaching the dome so you dont loose some of the illumination somewhere down in the underworld.

Step 7
Ok, last steps - load the model in layout and in TextureEditor set the Color channel of the Default surface (ground plane) to Image map,projection to Front and load the image or .avi you want to composite over.

This will map your ground plane with the background image so you dont need to texture it.

Also,make sure that the ReferenceCamera is set to the one you want to render from - just in case you've installed some security cameras to monitor the area for burglars.

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Step 8
Finally, select Layer2, press "p" and in the ObjectProperties panel - Render tab check UnseenByCamera to hide the dome so it doesn't show up in the render (it will still illuminate the scene,dont worry)

Switch off AffectDiffuse for all the lights in your scene but leave some AmbientIntensity cos it works very well in radiosity renders - add it to your taste though - EnableRadiosity while you're there

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Do a test render and adjust either the dome's Luminosity or the ground plane's Diffuse to match the brightness of the background picture and you"ll have seamless compositing right inside LightWave.

That"s all, if you run into any problems (but you won't, will you?) or if you have any comments on this you can email me.]