RE: [Algorithms] Grass blowing in the wind effect

[Blake S. <bse...@pa...>]

That's similar to how PDI did the fields in "Shrek"...
They used a spring system for all the grass, flowers & trees
and then embedded the spring system in a fluid flow simulation,
recorded all the resulting motion and "played it back" at
something like 1/10th speed...=20

A friend was at the local siggraph meeting where PDI gave
a talk about the "Shrek" production.

-----Original Message-----
From: Ratcliff, John [mailto:jra...@ve...]
Sent: Tuesday, July 10, 2001 4:20 PM
To: 'gda...@li...'
Subject: RE: [Algorithms] Grass blowing in the wind effect


I've been toying with the ideal of taking one of those water simulations
you
see, the 2d surface deformation stuff, and write a really fast version
of
that.  Then (somehow???) translate the current state of the surface
deformation into a translation on the verts in the grass.  This same
surface
deformation source data would be used to make trees blow in the wind as
well.=20

Could be expensive, but would sure make a cool looking wind effect.

John

-----Original Message-----
From: Jason Zisk [mailto:zi...@op...]
Sent: Tuesday, July 10, 2001 5:55 PM
To: Algorithms
Subject: [Algorithms] Grass blowing in the wind effect


I've got some pretty cool procedural grass right now.  Making it blow in
the
wind would put it over the top, I'd love to hear some ideas on a good
way to
do this.

My first thought was to add a little shear into the transformation
matrix
when transforming the vertices of the grass.  Initial tests show that
this
will work pretty well.  My problem is getting from a wind vector to a
shear
matrix.  Right now we store wind in a 3D vector for direction and a
float
for speed.  I can't seem to wrap my mind around how to put that into a
shear
matrix that I can use in the grass transformation matrix.

Thanks for any thoughts on this.

- Jason Zisk
- nFusion Interactive




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