PatchAnim

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Thanks for your interest in PatchAnim.

This tool creates a sequence of color blends using Bezier Patches. This sequence of blends is tweened and animated giving smooth transitions from one blend to another. Blend animations can be outputted to animated gifs, animated pngs, animated mngs or a series of gifs, pngs or jpegs.

Unfortunately gif files are 256 color images, and so you get some grainyness. If you have FireFox 3.0 with the APNG Edit plugin, you can see the following Animated Png, which is shown in 24 bit color. If you do not, you will just see a still image.

A Cubic Bezier curve is a curve defined by 4 control points. The curve goes thru both end points, and the curve is influenced by the two middle points. In fact the slope of the curve at the first point is equal to the slope of the line from the first to the second point. Similarly the slope of the curve at the end point is equal to the slope of the line from the third to the fourth point. Rather than calculating a point on a curve, this application uses the shape of the curve to determine a color. In the following diagram, the y axis denotes a color from black to a full primary color (red in this case). By using a curve, we can give a separate color for each section of the curve, as seen in the color blend below the curve.

Now this tool uses Bezier patches, not curves. A Cubic Bezier patch is a description of a 3D surface consisting of 16 control points. You can think of a patch as a set of bezier curves running in parallel along the x axis, and a cross cutting set of curves running along the y axis. (This is an over-simplification, and in fact incorrect, but is good enough to understand what this application is doing). Again, though, the z value in this application is mapped to a color, where values of 0 are mapped to black, and values of 255 are mapped to full color (in this case red). In the color blend samples, then, you can imagine that you are looking straight down on the patch from above. In this application, you can only move the control points in the z direction (into the screen or out of the screen), the x and y positions are fixed.

To accomplish creating the desired effect, three such patches are available, one for red, green and blue. Each patch only controls one primary color, and then the values from each patch is put together to generate one full color blend. Since the description of the blend is very succinct (just 3 * 16 points), It is very easy to generate in-between images from two separate blend descriptions.

February 23, 2008

December 27, 2008

January 2, 2009

If you would like to see the tool as it progresses, you can run the webstart version here.