Forums Technical Discussion Trying to understand bbox terms

Trying to understand bbox terms

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proceduralist
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While using Bbox expression, I come across the terms D_YMIN, D_YMAX, D_SIZE



Using the following terms for Y component of 'translate' option within 'transform' node, I have the box move as follows based on the expression as follows, typed .

bbox(0,D_YMIN) - Box moves down at a distance equals to half of its height. i.e. half of its dimension in Y direction. So a cuboid with a height of 5 units, will move down 2.5 units.


bbox(0,D_YMAX) - Box moves up at a distance equals to half of its height. i.e. half of its dimension in Y direction. So a cuboid with a height of 5 units, will move 2.5 units upwards.


bbox(0,D_YSIZE) - Box moves up at a distance equals to its height. So a cuboid with a height of 5 units, will move 5 units upwards.

What is the exact meaning of YMIN and YMAX? They seem to be half of the Y dimension but the 'MIN' and 'MAX' in their names hints to something else.




Edited by proceduralist - Aug. 3, 2022 03:04:27

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tamte
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archz2
What is the exact meaning of YMIN and YMAX? They seem to be half of the Y dimension but the 'MIN' and 'MAX' in their names hints to something else
they refer to Minimum and Maximum bounds value in corresponding axis of the bbox

in your case your box is at the center so it may look like they have something to do with half of the size
but if you move your box 5 unit box up by 2.5 for example, you will notice that YMIN is 0 and YMAX is 5, simply minimum and maximum bounds of the bounding box in y axis, etc
Edited by tamte - Aug. 3, 2022 03:10:42
Tomas Slancik
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proceduralist
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I am not able to understand still what exactly is YMIN and YMAX. I placed the cube at different height and added a short cuboid above a plane just to find the measure of the gaps.







-------

Okay. The bounding box isn't the outer enclosure that encloses the geometry. It also considers the empty void between the geometry and the origin?

Edited by proceduralist - Aug. 3, 2022 05:27:28
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BabaJ
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The bounding box isn't the outer enclosure that encloses the geometry.

It is.

It also considers the empty void between the geometry and the origin?

It doesn't consider the 'void' the way you think. It's not the bounding box itself with the void.

The MIN and MAX values are given in terms of global coordinates.e.g.(with box faces planar to global xyz directions) where is the top face in relationship to global center, where is the bottom face in relationship to global center, etc. This is where you are getting confused.

Put the following in a wrangle set to detail, and look at the detail geometry spreadsheet of the values.

v@Max    = getbbox_max(geoself());
v@Min    = getbbox_min(geoself());
v@Center = getbbox_center(geoself());
v@Size   = getbbox_size(geoself());

f@Max_Size = v@Size.x;
if(v@Size.z > f@Max_Size) v@Max_Size = v@Size.z;
if(v@Size.y > f@Max_Size) v@Max_Size = v@Size.y;
Edited by BabaJ - Aug. 3, 2022 09:19:04
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proceduralist
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Awesome. Now I get it. Thank you so much! I was unnecessarily mixing things up and muddying the water for myself. Putting screenshots for later reference.




Edited by proceduralist - Aug. 3, 2022 11:15:22
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