PDA

View Full Version : are light bleeding and highlighting done as 2d or 3d effects?



applesauce
01-28-2006, 03:02 PM
in the absence of shaders, for games that use these types of effects (halo, halo 2, mgs3, shadow of the colossus, etc), how is it done? as a 2d post-processing overlay, or with 3d sprites?

killerseven
01-28-2006, 04:30 PM
Not sure what you mean by highlighting, but light bleeding (bloom) is just a simple 2d effect that can be done without shaders.

applesauce
01-28-2006, 05:25 PM
highlighting as in the type of hdr seen in halo 2, or the xbox port of hl2. i get the idea that this is considered faked hdr, but i just don't know what else to call it.

killerseven
01-28-2006, 05:37 PM
yes that is all possible without shaders, and would be done as a 2d post process.

the key part of highlighting (tone-mapping) is determining the average brightness of the screen.

this would be done by down sampling the final 2d image of the scene to a relatively small size (32x32) and then reading back the video memory and calculating the average luminosity of the scene.

once you have that value you can then adjust the brightness of the scene relative to that value with a simple filter.

for more info there is a rough translation of some of the techniques used in shadow of the colossus here:
SotC (http://www.ga-forum.com/showthread.php/?t=78011)

applesauce
01-28-2006, 05:55 PM
awesome, thanks. another question. as seen here (http://www.watch.impress.co.jp/game/docs/20051207/3dwa14.htm) , how is that cross hatching achieved on the sword? obviously with a small repeated texture, but is this still a 2d post-process or not? it's part of the hdr effect in both sotc and halo 2, etc.

edit: as suggested by that thread, is this effect defined as part of the model data, like the rain "hit detection" in mgs2?

killerseven
01-29-2006, 05:01 AM
The bloom process sometimes contains a "star" filter that creates streaks of bloom. This is often used for car headlights etc.

This is quite expensive as it involves a lot of filtering, but again it does not require shaders.

However I doubt this is what is going on in SotC for the sword. My guess is they just define a 3d line for the sword, and distribute particles along it. They then adjust the colour and size of the particles based on some reflectivity value. The subsequent bloom process would help to fuzzy the whole thing up.

applesauce
01-31-2006, 08:43 AM
alright, thanks for all the help. i've edited it now, but i meant "effect" rather than "hand" in the addendum to my previous post. but i guess you got you that. anyway, thanks again.