I get this every now and then with procedural modelling in Houdini and I thought this time I'd ask if anyone knows why it happens, and maybe a solution to it. Does anyone know why one of these polys seems to be flipped? They all have the exact same nodes added to them but one is out of whack… I've tried reversing the sort order on the points but it has no effect.
The extrudes have their transform space set to local. If you set them to global, you'll have the same result, obviously. On local however, point order is taken into account. A procedural approach is not always the best option. I don't know what you're trying to model there, but if you don't need everything to be 100% procedural, just extrude them globally and move them up or down (edit node). My $.02
Edited by anon_user_89151269 - April 27, 2018 04:22:21
Hey thanks for checking that out. I get that procedural is not always the best approach, but am building games assets and sometimes it can be a huge time saver. This is just one of those things that pops up here and there and I’d love to know how to remedy it. If it’s winding the wrong way, is there a way to reverse that? Sort seemed to have no effect. Also could it be bug? It seems like a pretty unpredictable result.
They're all winding the same way - clockwise in this case. Otherwise you'd have flipped normals. What did you sort and how? When doing poly modeling operations, point numbers get mixed up, I don't think it's a bug. Some vex master might know a solution for this, but it doesn't seem trivial from here.
edit: Same result in XSI
Edited by anon_user_89151269 - April 27, 2018 11:31:50
peteski If it’s winding the wrong way, is there a way to reverse that? Sort seemed to have no effect. Also could it be bug? It seems like a pretty unpredictable result.
use Reverse SOP to shift your vertex by 2 units. However this only seems to work on isolated primitives as the Source Group does not seem to work in the Vertex: Shift mode. Might be a bug?
On a technical note, I am no expert but the direction is not the problem I think. Otherwise the primitives normal would be reversed/backfacing. As far as my fundamental 3d knowhow goes this works the same way for all 3d polygonal content. So the winding I always thought as where the Polygon starts and ends. The direction of that will determine which direction the normal of the polygon faces. (Thats why it matters which direction you draw a polygon when using curve sop or the stroke tools with closing the ends etc.) The vertex numbering (Not Point Numbers!) will always change when doing a reverse of polygons or shifting the vertex's with the reverse sop. I think you can display vertex numbers in houdini so you can visualize it for yourself. Hope this helps.
You can also check in other 3d Application and see when creating polygons clockwise vs counter clockwise.
edited to make clear I mean vertex numbers not point numbers
It's really interesting that the same ting happens in XSI. Good to know you can use the reverse sop to shift it like that, I was thinking of point numbers, that's why I was using sort but I guess it needs to be rebuilt to adjust the underlying vertex numbers and maybe the reverse sop (or rebuilding with Add) does that? Well that's awesome thanks for all the help!
Hope this helps. 