Shader/UDK - Atmospheric Sky Scattering - Code sections not available?

Ace-Angel · May 2012

Hey to all,

I was wondering if anyone knew a good way to substitute certain function or math for application that don't have certain functions available?

For example, I'm trying for a Atmospheric Scattering material in UDK, but there are snippets of code which don't work in UDK, like this for example:

float fFar = length( v3Vector );

Currently, UDK doesn't allow me to access the Length function, so I approximated it by using the 'Distance' function instead, but that doesn't seem right since my current output looks like a glow ball of fire.

This happens both for Planet and Sky based Atom-Scatter.

Incase you need to checkup the codes I'm referencing, here they are;
http://www.gamedev.net/topic/621187-sean-oneils-atmospheric-scattering/
http://forums.create.msdn.com/forums/p/9117/454655.aspx
http://stainlessbeer.weebly.com/planets-9-atmospheric-scattering.html
http://forum.unity3d.com/threads/12296-Atmospheric-Scattering-help

Cheers!

haiddasalami · May 2012

Hey Ace, if I remember right distance node comes in Unreal Units so you need to scale it.

Ace-Angel · May 2012

Hey Haid,

That's a start, but any ideas on how I would go about doing that? I'm not sure how or what UDK's values vs. others is, google is coming up empty. I'm guessing it's scaled to Max?

ambershee · May 2012

UDK has one UU = 1cm by default (this is documented). As for other applications and this shader, I couldn't say.

cptSwing · May 2012

i thought 1 UU = 2cm?

haiddasalami · May 2012

Hey Ace sorry cant be of much further help, maybe try making the length formula back up for the vector? so:

sqrt(x^2, y^2, z^2)

Brice Vandemoortele · May 2012

or: sqrt(dot(v,v))

ambershee · May 2012

cptSwing wrote: »

i thought 1 UU = 2cm?

In Unreal Tournament games it is. In Gears of War it is 1UU to 1/2 inch.

Froyok · May 2012

cptSwing wrote: »

i thought 1 UU = 2cm?

That's the case but :

UE3 treats one Max Unit as one Unreal Unit, regardless of what length the units were originally set to in Max.

Same case from Maya.

The Units are also dependent of the game you use because they are specified in the script files. Gears of war use character much taller than in Unreal Tournament.
The "mobile" gametype in UDK use a player size larger than in the UT DeathMatch gametype for example.

Ace-Angel · May 2012

Sooo...based upon all this information, at least on a shader level, I'm pretty much plugged in my dark hole (aka fucked?).

almighty_gir · May 2012

ambershee wrote: »

In Unreal Tournament games it is. In Gears of War it is 1UU to 1/2 inch.

1/2 inch != 1cm

1/2 inch = 1cm * 2.54 * 0.5 = 1.27

1UU in GoW = 1.27cm

cptSwing · May 2012

yeah, i've switched to max's generic units as well.. after having used cm's in max and doing the 'math' in my head, which in retrospect is a little convoluted

Shader/UDK - Atmospheric Sky Scattering - Code sections not available?

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