Hi(gh)!

With a new computer finally at hand, I wanted to upgrade my POVSolar 
(and, thus, also POVEarth) project, replacing the simple 2048 x 1024 
surface and clouds texture by a more sophisticated one. After adding 
separate textures for surface (i. e. land, sea and sea ice) and clouds 
(on a slightly larger sphere to make them float at 5 kms above the 
surface), I also want to add a "city lights" texture showing only up on 
the night side of Earth.

To achieve this, I added the "city lights" image_map as a new texture 
layer beneath the daylight surface image_map - but to make it appear on 
the night side only, I'll also somehow have to add a gradient pattern 
for the alpha channel of the daylight surface texture. Unfortunately, 
the official manual is silent about this - it only contains notes on 
assigning alpha values to index colours or using the alpha channel 
provided with the image file...

So, how can I add an alpha gradient to my daylight image_map?

See you in Khyberspace!

Yadgar

Post a reply to this message