Snow level from Mario Galaxy - How did they do it?

It looks to me like a simple particle effect. Whenever you move the wand over an area of snow, nearby particles fade out quickly to give the appearance that you cleared it away. Then over time they fade back in. It also looks like they use some simple physics to push particles around while they fade, but nothing too fancy. Given that this is the Wii I wouldn't imagine they're using any complicated tricks.

I agree; it looks like a simple particle effect for flakes and puffs, combined with texture splatting and a shader for the ground itself.

To me it looks like nothing but a dynamic texture / normal map that gets cleared by the cursor and then slowly fades in over time, with particles making it appear as if its coming off.

It's either a dynamic texture or a dynamic mesh from what i can see. some kind of morph attribute in the vertex definition.

There are defintely particles, and the texture does appear to change as well; there does not seem to be anything like a dynamic mesh, and I see no normal mapping of any kind.

I think that the planet texture is obtained using two textures blended through an alpha mask (terrain + snow). When Mario walks on the surface it acts like a "brush" clearing out the alpha mask and causing the snow texture to disappear. I think they did not use particles nor meshes... using particles for such an effect would be a waste, IMHO.

But I can see the particles; there is depth, fringes above the surface..it really looks 3D, not just a texture effect.

Mmm... maybe the particles are only spawned when Mario walks through the snow, but I do not think that the snow is entirely made of particles.

Must be a multitexture effect with some bumpmapping(not quite sure if the Wii can pull normal maps)

Can't be particles as it would require way too many and also the snow 'regen' is done in a "whole" layering effect not a per-sprite basis...

Still not 100% clear... must boot it on the Wii and examine some more!

BTW: there should be a rule that an AAA game after X million sales or whatever should release the source code!:)

I think the snow is a low resolution texture. (look at the edges in the screen-shots below:)


I don't think a particle effect would cause such artifacts. But we have all seen such edges caused by low resolution shadow maps.
There are also some simple (short living) particles showing how the snow is moved around.
I have not play the game and the video has not the best quality thus I'm not sure whether there is a depth but creating depth with a texture is pretty easy: one needs to render several layers with small z offset. (Just like how fur can be rendered)

How 'bout Mario and the cursor clearing up the snow? How is that done?

You have a clean ground texture and a snow texture... To obtain the snow covered ground you use two texture stages: the first is the base tex and the second is the snow texture blended through an alpha mask. The alpha mask (that could be stored in an alpha channel) is a grayscale image: where the mask is black no snow will be blended, while the white areas are snowy. To clear the snow, think about the cursor or Mario as a black airbrush that paint the mask. Painting the mask with black will cause the snow not to blend with the first stage.

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Original post by yogr ...

Just wanted to share my agreement with this. The blend artifacts at the edges of the 'brush' distinctly remind me of my own shabby terrain painting code [smile]