Snow Glitter

[cplusplus]

does anyone know a good way to produce a really nice looking glitter effect seen from snow as the camera moves about (remember the snow in the coca-cola bears commercial) without having the 'jitters' ? Im not sure what the best way to approach this is (ie, shader, effects anim, composite tricks) I dont want it to sparkle unless there is movement of the camera to simulate crystal reflections like real snow.. Thanks in advance for any help someone can forward.
Squag

[loky]

I don't know, I'm just throwing it there... maybe linking with an expression the position of the camera to some random or noise channel of the texture applied to the specular channel of the snow shader. Although I'm a bit sceptical about it. Or write a script that would create an OpticalFX lens flare on all values greater than r250 g250 b250 on the specular channel... yeah right, sci-fi ... forgive me, it's late and I don't have Maya to experiment...

[inti-sun]

I think I found a solution for you:

First create a plane and deform it a bit; that will be the snow surface. Then create a camera (camera1) and a light.
Now open the Hypershade and create a Blinn node with the following attributes:
- Color to White
- Ambient Color to a dark blue (remember the snow is blue in the shadow)
- Diffuse 0.9
- a fine and slight rock texture as bump map (Bump Depth 0.03)
- Eccentricity 0.5
- Specular Color to White

Create a 2D fractal node (fractal1) with these attribs:
- Threshold 0.85, Ratio 1
- Level Min 10 Max 15
- Animated ON
- Invert ON (in Effects)

Connect the fractal's output to the Specular rolloff of the Blinn node.

Open the Expression Editor, create a new expression named 'glitter' and enter this (make sure the names match):

fractal1.time = (camera1.translateX + camera1.translateY + camera1.translateZ)/3;

Now everytime the camera changes its position the Time attribute of the fractal texture will change. The Time attribute randomizes the fractal texture.
I divided by 3 to make an average of the position of the camera, but feel free to put a lower/higher value if the glitter is too fast/slow. Now assign the snow shader to the surface.
I didn't make any animation test so maybe you'll have to tune it a bit. But the concept is there.
You could have put another texture instead of the fractal (a 3D texture for example), but make sure it has a Time or Phase-like attribute that can be keyable.

Have fun,

Inti