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   * Subject: Seamless Waterfalls & Fire
   * Date:    Monday, 24 October 1994 22:45:31 [55]
   * From: (Shinobi)

First begin with a 2D outline such as the one below:

     |                     Z
     |                     |
     |                     |
     |                     Y-----X

This shape should be extruded by whatever distance you choose as the width of your waterfall.

Caller it whatever you like (I chose a very light blue), and turn the specularity way up so you can see how the light is affected by the texture. Now, add the BumpNoiz texture. Make the X, Y, and Z sizes something like 100,10,200, which basically give you long, thin bumps. Save this object as Waterfall.1.

Now, edit the texture axis and rotate it -120 degrees (you should see the axis roll forward, towards the left-side of this diagram). Save this object as Waterfall.2. Repeat again, saving the final object as Waterfall.3.

Rotate the axis locally around Y. This will cause the texture to rotate forwards to the camera, which is actually on the far left of the above diagram.

I've been asked to explain this in a little more detail, so I'll give what I can.

A 3D texture occupied 3D space. But the colours or bumps or whatever that appear occur only where the texture in 3D space intersects with the object. By positioning the texture axis away from the object, when you rotate the texture axis the intersection of the texture and the object changes. And because the texture occupies 3D space passing the texture "through" an object works the same as changing a "time" parameter that some textures have.

I'm not sure if that is a better explanation or not, so try this. Put a pencil or something on the screen, with the eraser at the texture axis. Now rotate the pencil around the screen, keeping the pivot point at the eraser. See how the pencil and object intersect at different points as the pencil is rotated? If you think of the texture as being full of bubbles, you can see that the object is actually "slicing" through the 3D texture when it intersets it (kinda like a CAT scan).

Enter the action editor and set the number of frames for, say, 90. Give some ambient light (say 40). Now, at frame 1 load your Waterfall.1 object. From frame 2 through 30, morph to Waterfall.2. From frame 31 through 60 morph to Waterfall.3. Finally, from frame 61 through 90 morph back to Waterfall.1.

Enter the stage editor and set the view up as you would like it. Do a test render to make sure all is well.

Render your animation, but leave off the last frame, so in a 90 frame animation you would render frames 1-89.

The trick is to offset the texture axis so that when it rotates the texture appears to flow along the surfaces it intersects. As I said, it works well with fire. You can use this technique to seamlessly morph a flame object (ala Steve Worley's example). Just make sure to place the axes of the textures where their rotation and intersection with the plane will give the appearance of movement.

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