Hello all
Three years late but better than never.
A student of mine was asking about selecting edges procedurally to polybevel.
After failing to find a solution with the group SOP, I found animatrix's wrangle solution.
At first, I too had the same weird 'shader error', but after some troubleshooting and clearing the extra brace added by vusta,
I managed to get things to work and added some comments in this example file in my journey to understand the code.
It is not fully procedural but it is a way forward instead of manual selection.

Hope it helps others jumping into this in future as I have done this Dec 2023.

p/s you have to click on the top right button in the point wrangle SOP to create the spare parameters after you paste the code.

Michael Ng
Nanyang Polytechnic

You could also use the facet sop like this…

To create the rock formation as shown it might be better to go by the displacement shader method as you would need a gazillion polys to get the details you see in that pic. Although most of the surface is flat, you need to get your polygon to the smallest chip on that rock.

Many thanks Tomas.
It works beautifully although it took me some time to make sense of the code.

Here is the working file with the solution and notes added for future reference and search.

MiKE

Hi edward
Thanks for the suggestion, I'm kinda lost in the VEX wrangling/coding world. I tried putting this code in the attribute wrangle after a connectivity node that gives me the ‘class’ attribute for each piece. But alas not getting the results. Some more advice please…

Run Over : Details(once only)
VEXpression:
if(@Cd[1]>0) i@redpiece=primattrib(0,“class”, @primnum,i@success);
if(@class==@redpiece) @Cd=set(0,1,0); //change to green to see better difference

Many thanks
MiKE

Hello Jeff,
There are already SOPs to do that e.g. file SOP, ROP out driver.
Here's a sample file to show you.

MiKE

Dear friends,
Would like your suggestions and help for a method to select voronoi fractured pieces by painting some points of the chosen pieces.

In the example file attached, I have fractured a box, then coloured it all black, painted some points of my chosen pieces with red, then promoted the Cd point attribute to primitives. This helps to spread the color to other points of the pieces but doesn't reach all of the connected primitives of the piece. The deletion at the end to just to isolate the chosen pieces but you will see I will not get the entire piece unless I paint every point of the piece.

I did try to use a foreach loop with attribute wrangle to go though each piece but can't seem to get the right code. Maybe I am heading the wrong direction cos there could be a simpler method.

Appreciate your suggestions.

MiKE

Thanks Jeff and Derrick
Great masterclass tutorials.
Good stuff.

Michael

You can partially fix the problem by putting in a rest geometry in the 2nd input of the divide node. My simed out animation is quite different from yours but I noticed that the geometry changes a lot from frame 44 when the glass hits the ground.

By plugging in the geo from frame44 the divide sop uses that as the rest geometry to do the convexing (it's in the help).

The topology of the input geometry changes again in frame 99, 133 and 188 from 21310 points to 21308 points so the divide will have different results again. (The reason for the popping in the video) So no fix for that even by switching to the new geos.

You could triangulate before dops if sim time is bearable.

For those who have been following this issue, hopefully we don't have to wait much longer.
Seems there is a fix on the way from Apple a long with other important things…

http://www.appleinsider.com/articles/09/10/16/apple_seeds_new_mac_os_x_10_6_2_beta_to_developers.html [appleinsider.com]

Michael