Static noise generation questions...

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Jan Barglowski (jan++at++archimedes.vislab.navy.mil)
Mon, 15 Jul 1996 16:38:59 -0700 (PDT)

Hi!

I'm trying to simulate a noisy video image. I'm generating the video
image with Performer, then adding a postdraw function to overwrite
a noisy image with alpha blending.

I use the glDrawPixel function to draw a generated random grayscale image
with alpha (to show noise level) using the GL_LUMINANCE_ALPHA format and
the GL_UNSIGNED_BYTE type.

Kinda works, but two problems:

1) The random image generation is slow. I use rand() for generating
random pixel values between 0-255 for each 256x256 of the pixels. Is
there a faster way, such as a "memory block" randomizer?

2) The alpha display has 4 discrete steps, rather than a continuous
blending. When I changed the format to GL_LUMINANCE it was continuous.
Is there some Alpha Blend mode I'm forgetting? I'm using a IR, if
that's any help...

Thanks for any hints, suggestions, etc...

jan.

-- 
Jan Anthony Barglowski	              jan++at++vislab.navy.mil
Animation & Computer Graphics         http://www1.ridgecrest.ca.us/~jan
Naval Air Warfare Center, China Lake  (619) 927-1057
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