how to grow a selection?

[meshsmooth]

How mite I go about growing or shrinking a point selection procedurally... and is there a method to do the same to a face selection?

[stevenong]

Hey meshsmooth,

After you select a point, change the selection type to polygon which will selection all polys connected to the point then change selection type back to points & now you'll have a "growing" points selection. Unfortunately, you can't use the same method for "shrinking" selection.

Cheers!

steven

[meshsmooth]

ok what if the selection came from a ray sop as a sphear moved accross a grid how would you grow the selection in that situation ?

[David Gary]

You can use the GroupSOP:

Turn on Enable under Edges, and adjust the Edge Depth.

But you will see that it doesn't work well, because the selection cannot grow simultaneously from two distant points...

So i created a Vex SOP using mainly neighbour functions, that allows you to grow selection.

check this:

(download the scene here)

It's only to grow selections.

But if you can grow, you can shrink, yes?

(i let you search and if you don't find, i'll give you the solution!)

Is it useful enough to make it an OTL (and submit it to odforce...) ?

(with some tweaks of course!).

(oh... for the faces convert Primitive Groups to Point Groups -> grow/shrink -> convert Point Groups to Primitive Groups

[meshsmooth]

I just read your past and am trying to work out the solution from what you have shown. Thanks for giving me half of the solution.... probably more useful than the whole solution.

[meshsmooth]

i am stumped as to how the "zero parameter" works

it enters the for loop and has one added to it somehow and can not be replaced with a constant inside the for loop....

i think i understand most of the rest of the resto of the network.

[David Gary]

As far as i remember ( i haven't got Houdini here), the zero parameter is a stupid parameter that can be removed ( it sets the initial value for the for-loop).

You can replace it with a constant VOP ( value set to 0).

An answer:

to shrink a selection is to grow the complementary selection...

hope it helps

[meshsmooth]

I am now working on making a vex sop to smooth values such as point colour or another attribute. This is an attempt to do what I do often in Photoshop to grow a selection. Turn the selection into a mask then Gaussian blur the image then threshold the image to make it hard selection again.

[David Gary]

My idea for smoothing values would be to replace the value at a point by the average value of the neighbors ( plus the current point) .

You can do that with a for loop through the neighbors.

(mathematically, it's not a gaussian blur or smooth but it is largely

equivalent)

[David Gary]

Oops, maybe too complicated.

Just use the SmoothSOP !