Re: [Algorithms] HDR translucency

[Jonathan B. <jo...@nu...>]

Bloom is generally done without alpha -- you render the scene to a 
render target, which you then use as a texture map, rendering into a new 
render target.  You basically sample the texture map with a blur filter, 
which gives you the bloom.

HUDs usually want alpha, but you probably do those after the bloom pass, 
thus they are probably down-converted to 8 bits per sample.

What you need alpha for is particles (smoke/sparks/etc), translucent 
surfaces or water, and lighting algorithms that want to implement 
multiple lights by rendering the lit surfaces multiple times and adding 
the results (very common these days).


Richard Mitton wrote:

> There's always a catch, isn't there..
>
> I suppose you could do it yourself -
> 1. Turn MSAA off.
> 2. Render scene in HDR, twice as big, with alpha stipple.
> 3. Use tone-mapping etc to convert HDR scene to A8R8G8B8.
> 4. Resize down to standard resolution.
>
> I reckon that might work.
>
> But thinking about it some more, if you can't do any alpha blending, 
> then how are you going to do the lovely bloom-style effects which make 
> it all worthwhile? I'm sure there's a huge flaw in this whole plan.
>