[GEM-dev] More Feature Requests posted to Source-Forge

[chris clepper]

On Jan 28, 2005, at 12:27 PM, B. Bogart wrote:

> Hey Chris,
>
> I was just guessing as to certain "possible" blend modes since a 
> pixelTANGO user asked me about it. (and its one of the few things that 
> Gem will not do that aftereffects can (and shadows, but I'm not asking 
> for that!).

Those blend modes are more than likely the Apple QuickDraw modes for 
CopyBits().  There's no point in attempting that for GEM, but you could 
probably come up with something comparable with abstractions.

> Ok so what do these blending modes actually do?

Pretty much exactly what they say - either take the source or 
destination alpha and set the blend based on that.

> Add, subtract, multiply could be pretty useful... there are the pix_ 
> objects for these operations but that is less flexible (texture only) 
> and perhaps will end up as shaders in the future?

A shader would be the best way probably, although I have no idea what 
the final implementation would involve.

> I just thought I'd put it on the map, but I'd much rather get support 
> to load alpha channels from files, and that point-in-volume test.

I think the file formats are the main limitation to loading alpha 
channels.  Have you tried None and Animation codecs in Quicktime?  
Those should retain the alpha.

> did you see my vertex array requests on source-forge?

No, can you post them here?

cgc