Can someone give me a hint of how I can break a plane to simulate the effects of breaking a window into small pieces with random size?

there is the “breaking ice” legacy tutorial.
http://www.sidefx.com/community/learn/effects/index.html [sidefx.com]

this should get you started, in addition search for the cleave sop, its somewhere on odforce, I believe.

You can also search the mailing list archive, there was some discussion about this, if I remember correctly

Hope this helps
Achim

How about L-system? Does any one know how I can do the window breaking effects with L-system? because I do not want the pieces look too blocky

Do you mean to use L-system tree to simulate random growing cracks on the glass surface to create more uneven shards when breaking the glass?

That would be interesting if L-system tree can be applied to a surface!

I've never looked at the breaking ice tutorial but why can't you take a 2D Lsystem, project and/or extrude, and then cookie?

How do you create a 2D Lsystem? Does it involve writing a special rule?

No, it just involves making your rules so that they don't come out in Z. In the LSystem SOP parameters pane, expand the Presets toolbar. Under the Presets menu, you'll find a few examples.

the + and - deal with left/right (2d) rotation of the branch while the following deal in the 3d:

& Pitch up
^ Pitch down
\ Roll clockwise
/ Roll counter-clockwise
| Turn 180 degrees
* Roll 180 degrees
~ Pitch / Roll / Turn random amount

hth,
dave

You can try Suart Ramsden's Clave Sop [odforce.net]

Crap! Never mind that. I've just tried it myself and it turns out that this SOP
only works with Houdini version 5.5.226 and 5.5.52