View Full Version : Grass on the Wind with Cloth FX

03-01-2007, 06:06 AM
I must make one thing in projects.I have grass who was made on polygons[grass made on sasquatch it can't be used in this project]and I must make animation who will be showing grass who is rolling on the wind. Making a wind was easy but making a rolling grass is not so easy. For this I used Coloth FX and results are not good. I used this parameters:
Basic Tabs:
Weight 0.4 [If I make this parameter for 0.1 fixed area disappeared]
Spring 1
Viscosity 1
Resistance 4
Sub 4000
Hold 10000
Collision Tab:
Collision Detect: grass surface
Exclusive collision wind
Collision Offset 200 mm
Bound 100%
Friction 0
Fix force 100
Advance TaB
Resistance Mode : Polygon
Mode Ration 50
Compress Stress 30%
Stretch limit 100%
Polygon 100%
With this parameters everything looks bad and I'm not happy. Maybe someone have any ideas or sulotion how to make it ??

03-01-2007, 06:08 AM
If some one what I can send scene file with this grass and wind.

03-01-2007, 07:06 AM
Why not use a texture displacement instead? Have falloff down the y axis (or use a weight map falloff) so just the tips are affected. PM me if you want further help.

bob anderson
03-01-2007, 04:53 PM
Why not use a texture displacement instead? Have falloff down the y axis (or use a weight map falloff) so just the tips are affected. PM me if you want further help.

This works well, but you have to actually model the grass.. here's a quick way to do this. I use a series of connected 2 point polygons (lines) Start with a single centered point. Hit <p> on your keyboard to convert it to a polygon. Extrude the point straight up, hit <n> to open the numeric panel, and enter 6 or 8 sides. (the more the better, but you are going to wind up with LOTS of polygons in the next few steps.) Once extruded, the point becomes a series of connected lines.

Next I use the array tool to make a field of these lines. (Array on x and z only, and you'll have to enter a manual offset, because lines have no actual dimension, so no matter what you enter under Automatic, the new lines will always occupy the same space.)

Next.. select all the points , except the bottom most ones. This keeps the grass bases all stuck in the ground. Then jitter the selected points. (I usually use the Gaussian mode.. experiment with values, as the amount of jitter you use will be dependent on the size of the object.)

Load the result into layout.

Apply a displacement map, setting the texture center to the height of the grass, and use a texture fall off so the texture is gone by the time you get to the base of the grass.

As for surfacing, the actual appearance of the grass is mostly dependent on an Object Property, not a surface attribute. Go to obj properties, and edges, and set your particle/line thickness to large.. or medium... Figure out what you like best, and remember that you can manually enter 4 or 5 to make them even thicker. I usually use a Surface colour where the bases are dark green, the middles a more grassy colour, and the tips a little more yellow green, using the gradient tool.

Once everything is set, animate the Displacement map, and you have grass blowing in the wind.

Hope this helps in your project,

Bob Anderson