* Subject: Re: HALO AROUND LIGHT IN IMAGINE * Date: Mon, 19 Sep 1994 00:31:49 -0400 (EDT)  * From: firstname.lastname@example.org--- METHOD #1 (The Pain in the A$s Radial Texture Method)---------
Create a disk utilizing Imagine's standard Disk parameters.
Copy the disk and scale the new one by a factor of two.
Copy the larger disk and scale the new one by a factor of four. You should now have three disks of varying size.
Position the disks so that the smallest is in front of the middlesized. The middlesized is in front of the largest.
Make the smallest disk Bright with a Color of 255,255,255. Also, make it a Lightsource.
Apply Radial textures to the middlesized and largest disks.
The middlesized disk should be Bright and have a color of 150,150,255. The Radial texture should be set so that the disk's transparency is set to 0,0,0 at the center. Create a transition distance over the radius of the disk so that transparency is 255,255,255 at the disk's edge. You want the disk's color to fade as it moves toward the edge of the disk.
The larger disk should be Bright and have a color of 255,255,255, and a Transparancy of 170, 170, 170. Set the Radial texture so that the color fades to total transparency (255, 255, 255) at the disk's edge.
Transform the smallest disk's axis ONLY. Bring up the Transformation Requester, and Rotate the Z axis 180 degrees. Select the Transform Axis Only button and Perform. The disk's Y-axis should be pointing exactly opposite the other disks' Y-Axis.
Group the three disks together using the smallest disk as the Parent. This is a basic "Light w/halo" object. When rendering it be sure to always point the Y-axis at the camera. It's easy to do. Just Align Y-axis to Track to Object Camera.
Render that, and see what you get. In this example the smallest disk acts like the bright lightbulb, the second disk acts like the film burn area, and the third disk acts like the atmospheric dispersion area. This object, being 2D, has some limitations.
A primary limitation is that this object only works well in Scanline situations. This is because in Trace Mode the two larger Radial mapped spheres block the smaller disk's light travelling backwards. To work around it create an axis, make it a Lightsource, place it behind the larger disk, and group it to the smallest disk. It isn't infallible, however...
Experiment with values. The Color values given above were for a standard high intesity lightsource. Always remember what your lightsource would look like in the real world. In the case of a red exit sign, make the Color values predominently red, and substitute a polygon created "EXIT" object for the first disk. Or something like that...
--- METHOD #2 (The Fog Method) -----------------------------------
Create a primitive sphere. Make it Bright with the Color values 255,255,255.
Copy the sphere and scale it slightly larger than the original sphere primitive. Make this sphere a Fog object by experimenting with Fog Length values. Color it as necessary.
For those with Imagine3.0 assign the Ghost texture to the foggy sphere.
Experiment with values. I haven't actually tried this yet, but it should work...
--- METHOD #3 (The Haze Method) ----------------------------------
Use Global FX Haze to fuzz up your exit sign.
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