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View Full Version : Instancing alignment: align to normals



jeric_synergy
09-09-2016, 06:01 PM
When I'm Distributing by Polygons, and Aligning by Normals, why are my instances not lining up along the normals of the polygons?

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Snosrap
09-09-2016, 06:39 PM
The instanced objects need to be modeled "Y" up in orientation you desire.

jeric_synergy
09-09-2016, 07:14 PM
The instanced objects need to be modeled "Y" up in orientation you desire.

Soooo, NOT along the Z axis (like everything else)?

Rephrased: the Y axis gets aligned to the normal?

erikals
09-09-2016, 08:36 PM
this happens in another situation too, where Z is Y, and the other way around. can't recall where.

can be confusing, not sure if that is logic or not.

prometheus
09-09-2016, 09:21 PM
This is pretty much the same as with place mesh, direction goes in y axis, and it respects rest to ground, so for placing against normals exact surface, it looks for the y-origin and y-direction as pivot point.

jeric_synergy
09-10-2016, 12:33 AM
The instanced objects need to be modeled "Y" up in orientation you desire.

Thanks, Snosrap.
++++++++++++++++
Next issue. ::sigh:: Taking Snosrap's advice, I reoriented the object and reapplied it as an instance. Due to its shape and the deformation, it was hard to tell how it was being oriented on the normal, so I added a small bit of geometry, the small pink sphere, as a marker.
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Note how in the 12 o'clock position the Instance is facing one way, while on the very next polygon clockwise it is turned on H 180. Basically, half the Instances face one way, half another.

What evaluation is changing that causes the rotation to be altered like this? The instancing object is a simple 18 sided Disk with the endcaps removed.

lertola2
09-10-2016, 08:33 AM
What evaluation is changing that causes the rotation to be altered like this?

I don't know this. Maybe its based on the point order of the polygons or their orientation in space. But you can create polygons that explicitly define the heading direction of the instances by making quads with one short edge. Use the edge alignment option in the rotation tab. Then the heading of the instances will point the +Z direction toward the short edges of the polygons.

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Snosrap
09-10-2016, 06:28 PM
Thanks, Snosrap.
++++++++++++++++
Next issue. ::sigh:: Taking Snosrap's advice, I reoriented the object and reapplied it as an instance. Due to its shape and the deformation, it was hard to tell how it was being oriented on the normal, so I added a small bit of geometry, the small pink sphere, as a marker.
134413

Note how in the 12 o'clock position the Instance is facing one way, while on the very next polygon clockwise it is turned on H 180. Basically, half the Instances face one way, half another.

What evaluation is changing that causes the rotation to be altered like this? The instancing object is a simple 18 sided Disk with the endcaps removed.

Does the the World, Local or Parent settings in the Instance panel make a difference?

jeric_synergy
09-10-2016, 07:21 PM
Does the the World, Local or Parent settings in the Instance panel make a difference?
Remember, I'm not looking for a solution per se, but more of an explanation. That said:

I haven't tried that yet, but using EDGE ALIGN rather than NORMALS (Alignment dropdown) makes them all behave consistently. I don't know why: I'm told (thanks, lertola!) that one edge of the hosting polygons should be shorter to use EDGE ALIGN, and these should.....well, opposite edges should be equal, so there shouldn't be a bias towards one Heading over another, although "fore-and-abeam" might have a bias.

Will have a loot at the coordinates mode next....still, it's baffling....