Rectangular Coordinate Transformation


The first entries are rotation values around the X, Y, and Z axes. Think of your starting image as a flat map: the X value tilts the bottom of your monitor towards you by X degrees, the Y value pulls the left side of the monitor towards you, and the Z value spins it counter-clockwise. Note that these are NOT independent rotations: the image is rotated first along the X-axis, then along the Y-axis, and finally along the Z- axis. Those are YOUR axes, not those of your (by now hopelessly skewed) monitor. All rotations actually occur through the center of the original image. Rotation parameters are not used when a ray tracing option has been selected.

Then there are three scaling factors in percent. Initially, leave the X and Y axes alone and play with Z, now the vertical axis, which translates into surface "roughness." High values of Z make spiky, on- beyond-Alpine mountains and improbably deep valleys; low values make gentle, rolling terrain. Negative roughness is legal: if you're doing an M-set image and want Mandelbrot Lake to be below the ground, instead of eerily floating above, try a roughness of about -30%.

Next we need a water level -- really a minimum-color value that performs the function "if (color < waterlevel) color = waterlevel". So it plots all colors "below" the one you choose at the level of that color, with the effect of filling in "valleys" and converting them to "lakes."

Now we enter a perspective distance, which you can think of as the "distance" from your eye to the image. A zero value (the default) means no perspective calculations, which allows use of a faster algorithm. Perspective distance is not available if you have selected a ray tracing option.

For non-zero values, picture a box with the original X-Y plane of your flat fractal on the bottom, and your 3D fractal inside. A perspective value of 100% places your eye right at the edge of the box and yields fairly severe distortion, like a close view through a wide-angle lens. 200% puts your eye as far from the front of the box as the back is behind. 300% puts your eye twice as far from the front of the box as the back is, etc. Try about 150% for reasonable results. Much larger values put you far away for even less distortion, while values smaller than 100% put you "inside" the box. Try larger values first, and work your way in.

Next, you are prompted for two types of X and Y shifts (now back in the plane of your screen) that let you move the final image around if you'd like to re-center it. The first set, x and y shift with perspective, move the image and the effect changes the perspective you see. The second set, "x and y adjust without perspective", move the image but do not change perspective. They are used just for positioning the final image on the screen. Shifting of any type is not available if you have selected a ray tracing option.

3D Color Parameters

You are asked for a range of "transparent" colors, if any. This option is most useful when using the 3D Overlay Mode . Enter the color range (minimum and maximum value) for which you do not want to overwrite whatever may already be on the screen. The default is no transparency (overwrite everything).

Now, for the final option. This one will smooth the transition between colors by randomizing them and reduce the banding that occurs with some maps. Select the value of randomize to between 0 (for no effect) and 7 (to randomize your colors almost beyond use). 3 is a good starting point.

That's all for this screen. Press enter for these parameters and the next and final screen will appear (honestly!).

Light Source Parameters

This one deals with all the aspects of light source and Targa files.

You must choose the direction of the light from the light source. This will be scaled in the x, y, and z directions the same as the image. For example, 1,1,3 positions the light to come from the lower right front of the screen in relation to the untransformed image. It is important to remember that these coordinates are scaled the same as your image. Thus, "1,1,1" positions the light to come from a direction of equal distances to the right, below and in front of each pixel on the original image. However, if the x,y,z scale is set to 90,90,30 the result will be from equal distances to the right and below each pixel but from only 1/3 the distance in front of the screen i.e.. it will be low in the sky, say, afternoon or morning.

Then you are asked for a smoothing factor. Unless you used Continuous Potential when generating the starting image, the illumination when using light source fills may appear "sparkly", like a sandy beach in bright sun. A smoothing factor of 2 or 3 will allow you to see the large-scale shapes better.

Smoothing is primarily useful when doing light source fill types with plasma clouds. If your fractal is not a plasma cloud and has features with sharply defined boundaries (e.g. Mandelbrot Lake), smoothing may cause the colors to run. This is a feature, not a bug. (A copyrighted response of [your favorite commercial software company here], used by permission.)

The ambient option sets the minimum light value a surface has if it has no direct lighting at all. All light values are scaled from this value to white. This effectively adjusts the depth of the shadows and sets the overall contrast of the image.

If you selected the full color option, you have a few more choices. The next is the haze factor. Set this to make distant objects more hazy. Close up objects will have little effect, distant objects will have most. 0 disables the function. 100 is the maximum effect, the farthest objects will be lost in the mist. Currently, this does not really use distance from the viewer, we cheat and use the y value of the original image. So the effect really only works if the y-rotation (set earlier) is between +/- 30.

Next, you can choose the name under which to save your Targa file. If you have a RAM disk handy, you might want to create the file on it, for speed. So include its full path name in this option. If you have not set "overwrite=yes" then the file name will be incremented to avoid over-writing previous files. If you are going to overlay an existing Targa file, enter its name here.

Next, you may select the background color for the Targa file. The default background on the Targa file is sky blue. Enter the Red, Green, and Blue component for the background color you wish.

Finally, absolutely the last option (this time we mean it): you can now choose to overlay an existing Targa-24, type 2, non mapped, top-to- bottom file, such as created by Fractint or PVRay. The Targa file specified above will be overlayed with new info just as a GIF is overlayed on screen. Note: it is not necessary to use the "O" overlay command to overlay Targa files. The Targa_Overlay option must be set to yes, however.

You'll probably want to adjust the final colors for monochrome fill types using light source via color cycling . Try one of the more continuous palettes ([F8] through [F10]), or load the GRAY palette with the [A]lternate-map command.

Now, lie down for a while in a quiet room with a damp washcloth on your forehead. Feeling better? Good -- because it's time to go back almost to the top of the 3D options and just say yes to:


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Noel Giffin,
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