Deleting the shorter edge of a rectangle

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Hello dear Houdini artists,

I'm relatively new to Houdini and still struggling with some of the more basic concepts.

My problem is the following: I have a rectangle (created from a bound node) and I want to delete either the shorter or the longer edge of that rectangle, so that I can then create a vector that shows me the orientation of that rectangle.

How would I go about doing that? I have measured the lengths of the rectangle with a convert line node, but how can I compare the 2 lengths and remove one or the other?

Is there a better way to go about this?



I would really appreciate some help with this.

Best regards,

Julian

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rectangle_problem.JPG (24.8 KB)

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julianbragagna
I have measured the lengths of the rectangle with a convert line node, but how can I compare the 2 lengths and remove one or the other?
You can then use Sort SOP to sort prims by your length attribute

And then Blast SOP to keep or delete primitives: 0 1
Tomas Slancik
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julianbragagna
I have measured the lengths of the rectangle with a convert line node, but how can I compare the 2 lengths and remove one or the other?
You can then use Sort SOP to sort prims by your length attribute

And then Blast SOP to keep or delete primitives: 0 1
As those will be the shortest 2
Tomas Slancik
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tamte
You can then use Sort SOP to sort prims by your length attribute

And then Blast SOP to keep or delete primitives: 0 1
As those will be the shortest 2

That's a great solution! How would I go about applying this on scale, for an arbitrary number of rectangles?
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easiest would be to run it through For Each Block that iterates per rectangle
Tomas Slancik
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julianbragagna
How would I go about applying this on scale, for an arbitrary number of rectangles?

using the rest length prim attribute generating form the convertline can sort multiple rectangles with the same blast or delete node
if u precisely need per rectangle sort then go with tamte suggestion
Edited by Sweetener - May 7, 2021 10:59:23

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use rest length from convert line.png (575.1 KB)

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Naga Pavan
can sort multiple rectangles with the same blast or delete node
Only if no rectangle has larger edge smaller than other rectangle's smaller one
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julianbragagna
Is there a better way to go about this?

To obtain the short direction you could unroll your rectangles and subtract their minimal position from the primitive's center:

v@dir = normalize(minpos(1, v@P) - v@P);

To obtain the long direction you would calculate the cross product of the short direction and the primitive's normal:

vector nml = prim_normal(0, i@primnum, vector(0.0));
v@perp = normalize(cross(v@dir, nml));

Attachments:
rect_dir.hipnc (96.9 KB)

https://procegen.konstantinmagnus.de/ [procegen.konstantinmagnus.de]
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Alternatively you could iterate through the primitive's points, and compare the subtractions of their point positions:

int pts[] = primpoints(0, i@primnum);

vector pos_0 = point(0, 'P', pts[0]);
vector pos_1 = point(0, 'P', pts[1]);
vector pos_2 = point(0, 'P', pts[2]);

vector dir_10 = pos_1 - pos_0;
vector dir_21 = pos_2 - pos_1;

v@dir_short;

if(length(dir_10) > length(dir_21)){
    v@dir_short = normalize(dir_21);
}
else{
    v@dir_short = normalize(dir_10);
}

Attachments:
rect_dir_pts.hipnc (100.6 KB)

https://procegen.konstantinmagnus.de/ [procegen.konstantinmagnus.de]
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tamte
yeah, if rectangles vary in size it fails, I realized sorting with the attribute and deleting 0 1 per connectivity is safer

Konstantin Magnus thank you sharing your sorting methods
Edited by Sweetener - May 9, 2021 11:11:03
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