While working on an image (Disaster!), I became frustrated with
Imagine's Nebula texture. The texture creates a nice wispy, nebulous
look, but is inadequate for creating realistic astronomic nebulae. So,
I set out to discover a better way. After many hours of experimenting I
was ready to give up when a sudden inspiration hit. I tried applying
Pebbled to a fog object, then applied Ghost, and rendered. My jaw hit
the floor.
So what do bump textures like Pebbled have to do with fog
objects? The key to the resulting affect is Ghost. The Ghost texture
was designed to fade a fog object at its edges. In order to determine
what part of the object is facing the camera, and what parts of the
object are its 'sides', the texture looks at the angle the ray from the
camera makes with the surface normal. The surface normal is an
imaginary line that is perpendicular to the surface of the face
(triangle) being rendered. In other words, a line pointing directly out
from the surface. If the angle between the camera ray and the normal
direction is 0.0, the object is facing the camera. If the angle is
90 degrees, the face being shaded is currently on the side of the
object, etc. When Ghost is applied to a fog object, as the angle
between camera ray and normal increases, the fog length is adjusted
according to the values set in Ghost's requestor. Coincidentally, bump
textures do their magic by adjusting the surface normal of the point
being shaded. When Pebbled is applied to an object, it alters the
surface normal to give the illusion of bumps on the object. When Ghost
is subsequently applied, it finds modified normal values, which alter
where Ghost does its fog thinning.
Enter Detail editor:
- Add a primitive sphere.
- Use Magnetism or Deform Tool to distort the sphere into a shape
500 units long, 150 high and 100 deep.
- Add the Wrinkle texturew as follows:
Column One Two
____ ____
60 -1
8 0
8 0
1 -1
0.5 0
4 0
0.1 0
0.4 0
- Add the Fakely texture:
Column One Two
____ ____
0 60
0 0
0 150
0 255
0 180
0 200
0.9 0
0 0
- Make the object a fog object, set the object's Fog Length to 120.
- Add the Ghost texture and use the following settings:
Column One Two
____ ____
1500 0
0.35 0
0 0
0 0
0 0
0 0
0 0
0 0
In most cases it is best to set T to 1.0. This means the Fog
Length At T value will be specifying the fog length at the side of the
object, wich makes it easier to predict the results.
- Add 3 more instances of the Wrinkle texture:
Column One Two
____ ____
60 -1
20 0
20 0
1 -1
0.3 0
4 0
0.05 0
0.4 0
For more variety in the clouds, add more instances of the bump
Wrinkle texture.
Column One Two
____ ____
30 -1
8 0
8 0
1 -1
0.5 0
4 0
0.1 0
0.8 0
And a fourth Wrinkle texture:
Column One Two
____ ____
10 -1
10 0
2 0
1 -1
1 0
4 0
0.4 0
0.7 0
- For even more variety, add the Bump Noise texture as follows:
Column One Two
____ ____
40 0
10 0.3
5 0
0.4 0
0 0
4 0
3 0
1 0
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