Semi Transparency in Overlay Planes

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Julia Ellery (modellers++at++intersim.co.uk)
Wed, 02 Apr 1997 14:35:08 +0000


Hello

Can anyone tell me how to make an image I am drawing in the overlay
planes semi-transparent so that I can still see the underlying database
through it?

The image in question is an array of colour index pixels in the range
1 to 7. I use a call to pfuMapWinColors to setup the colour map starting
at index 1. My image has specially been "fixed" just to have 7 colours
in but this could be reduced to 5 if necessary. I am using the
glDrawPixels call to draw the image. I am currently doing this
in the perfly code, file perfly.c, routine drawOverlayName. The image
is currently being drawn ok but I want it transparent rather than solid.

Can anyone help?

Thanks to those who replied to my question about EarthSky and database
tearing. I actually wrote on behalf of a colleague who is abroad. I have
not forgotten - just been sidetracked for a while.

Regards,

Julia Ellery,
Senior Visual Software Engineer,
Intersim Limited, Units 7-8, Thorgate Road, Littlehampton. Sussex. UK
Tel: +44 (0)1903 733428
Fax: +44 (0)1903 730246
email: modellers++at++intersim.co.uk

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