MSP: Twinkle a Star....using REGION

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MSP: Twinkle a Star....using REGION

Post by sjj1805 » Thu Nov 02, 2006 5:01 pm

Author: Terry Stetler
In another thread this question was posed;
Martin Keith wrote:What would be the best way to create a "twinkle" on a lone star on a black background in an introduction? I have been experimenting with this in CG Infinity and the results were resonable but if there is an easier or different way to achieve a better result I would be very grateful for any help.
There are a couple of ways to do this in either MSPro7 or MSPro8.

One would be to use the Star video filter and keyframe it to create and vary the intensity/size/color of one or more stars, but that's too simple :)

More instructive is to use this as a way to teach the use of the REGION function for video filtrers like Brightness & Contrast. Here's the step by step;

1. draw your starfield in the same size as your video frame and save it as a BMP.

I like to use a tool like Diard Softwares Universe Image Creator to do this as it lets one add features to the image like starfields, nebulae, galaxies, gas clouds, globular clusters, planets etc. While full features require paying and registering, the shareware version is more than enough for 90% of people as it can still do starfields, nebulae, gas clouds and globular clusters;

http://www.diardsoftware.com/index.html

Example:

Image

The below image wasn't done in UIC, but in PhotoImpact using the Particle/Stars tool. This "look" is simpler for purposes of an online example w/small images;

Image

2. load the saved image into your image editor and ERASE to BLACK all but the star you're interested in. Easiest done by choosing a large brush and black as the color;

Image

3. now choose a brush about the same size as your star and set the image editor to feather the edge of the brush. In Photoshop this is done by choosing a gradient brush, but in PhotoImpact this is set by a slider in the brush toolbar. Now pick the color WHITE and just stamp directly over the star. This was done in PhotoImpact with a brush size of 20 (zoomed for clarity);

Image

Now save this image as a BMP but with a different name. This is your matte.

4. now that the drudgery is over here's the fun part. Place the starfield on Va or Video1 (depending on your version) and open the context menu's Video Filters dialog. Pick the Brightness & Contrast filter.

5. still in the Video Filters dialog click the REGION button. In REGION set the Type to "Gray Key" and the Mask to "Image Matte", which will bring up a file dialog from which you load your matte image. Set the Threshold to a rather low, but steady, value. I use about 20 or so.

6. now keyframe the Brightness & Contrast filter to suit. I keep the brightness no higher than +20 and with a minimum of -20 to -50. Set the gamma and contrast to be constant. More keyframes closer together make for a faster, more natural looking twinkle.

Here's what you'll get;

http://digitalvideo.8m.net/tutorials/tw ... /stars.wmv

Full sized bitmaps used in this tutorial;

http://digitalvideo.8m.net/tutorials/tw ... /stars.bmp
http://digitalvideo.8m.net/tutorials/tw ... smatte.bmp

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