modifiers - mask - vertex weight

1. add a vertex group to the plane

1. add modifiers – mask (turn it of for now)

2. and vertex weight edit

3. in vertex weight edit under Vertex Group: select the vertex Group created earlier.

1. still in vertex weight edit  set the Falloff Type: to Custom Curve.

1. still in vertex weight edit  – under Custom Curves – create a texture mask.

1. in Mask  select the Vertex Group: Group or what ever it is called and turn the Mask back on.

1. in vertex weight edit

– adjust the Add Threshold number

– and adjust the custom curve’s Curve

to get the masking resault