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   * Subject: Nebular Texture
   * Date: Sat, 30 Apr 1994 16:42:54 -0400 (EDT) [49]
   * From: Andrew McDonald <>

I've just been playing with the Nebular texture to create a little animated smoke. Works great, and I just thought some of you with 3.0 might make some use of this info.

Remember to render fog objects in front of a background object, and that this texture will apply to the area bounded by the texture axis, not the entire object. Scale the texture axis to affect the shape of the fog.

General Notes:

Noise 1 seems to affect the quality of the swirls. Higher numbers adjust the thickness and reduce the transparency. Noise 2 affects color transitions, color intensity of nebular color as set in texture requester, and color mixture, or grain. Grain appears as a very pointillated surface, as if there are thousands of dots of color rather than a smooth gradation or defined boundaries between object and nebula colors. Higher numbers of Noise 2 intensify the nebular color and increase grain.

Fog length and the 'T' value work together to determine amount and density of the fog appearing on the object. For stills I would set the 'T' value between .6 and .8, object fog length at .1, and adjust the 'Fog Length at T' to get the right density of fog. I would use the 'T' value combined with some of the noise values to create a fluctuating fog, or even to morph from a dense fog to one very nearly dissipated.

A nice, swirly smoke might use the following attributes in the nebular texture requester. I used these on a sphere primitive with diameter of 300, so use that number as a reference to fog length.

   Object color:
   Object Fog length:
   Nebular attributes:
   Fog Length at T:500
   Noise 1 Magnitude:5.0
   Noise 1 Velocity:1.0
   Noise 2 Magnitude:.2
   Noise 2 Velocity:10.0

The texture axis forms a square completely inside the sphere object, whose corners touch the inside surface of the sphere.

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