# How to get planar quad meshes?

Hi,
I have a project to create a 3D surface with 2D panels (with laser cutting). I actually know how to do it with triangular meshes, but I would prefer quads.

I want to obtain planar quad meshes and edge maximum lenght fixed (10 for ex.)

Initial surface :

Generate Mesh fromm Nurb surface

Then I used the “reduce mesh option” with “planar only” wich create some triangles :

I want to export this mesh to a .dxf file. or.3ds file (to use in sketchup).
But when I open it on an another soft (sketchup), I have only triangles :

Is there any solution to create perfect planar quads ? It looks that the one created on rhino are not recognised as “planar” in sketchup ?

Thanks,

Vincent

Triangles are planar by definition. Quadrangles need not be. For example: take an ordinary rectangular sheet of paper and tape or tack 3 corners to the table. It’s a planar quad, right? Now lift up the 4th corner. Still a quad, but - oops - no longer planar. In fact there is a kink in it connecting the two corners which are adjacent to the lifted corner. That kink defines what is essentially a 5th edge which would be the joined edges of two triangles which ARE planar.

The implication here is that ANY surface can be tiled (meshed) with triangles built from 3 corner points which lie ON the surface. This is not true in general for the 4 points of quads, though there are many surfaces for which it can be true. Thus, in general, a system for tiling a surface with quads must choose between maintaining the the corners as points that are actually ON the surface (and losing planarity), or maintaining the planarity and losing the strict location of all corner points on the original surface. Which is better depends on what you want to do with the mesh downstream.

So, no, there is no solution to creating perfect quads in all cases. You need to choose which approximation is more important for your situation and (here’s the problem) your software’s mesher must be able to handle either case. Rhino’s builtin mesher is a one-size-fits-all which will give triangles whenever it can’t meet the tolerance spex you’ve given it using quads. The panelling tools that Rajaa wrote give you better control over this.

As to Sketchup making everything into triangles, I suspect that’s just what it does with a set of points defining a surface. I can’t say for sure as I don’t use Sketchup.

There may be two limitations:

1. Sketchup may not use quads but only triangles (like AIW I don’t use Sketchup). If Sketchup displays quads, it may actually be using triangles in the background and be hiding the middle dividing line of the quad (3dsmax can do this).

2. Your output file formats of .dxf and .3ds only use triangles, I think. I could be wrong on this. If you can, output to an .OBJ file, which will hold quads, and try importing that .OBJ file into Sketchup. Conversely, Rhino can export directly to a Sketchup file. Try that too.

Matt

ANY trimmed edges will have triangles, btw-

No way around it in rhino, unless the surface can be shrunk or rebuilt to being just a non trimmed 4 sided patch.

I am working on a project now that involved panelizing an irregular surface into planar quads, and I found paneling tools to be just what I needed. There is a panel command called ‘panel planar quads’ that should give you the outcome you’re looking for.

Hi Vincent,

maybe the tool _-QuadrangulateMesh is helpful for your need. It has a planarity option, maybe it can remove the triangles after reducemesh.

Hi Micha,

Initial surface :

After reducemesh (planar option)

Adn then after quadrangulateMesh with planarity = 0 and rectangulary = 10.

Wich looks great, BUT if i do again a recemesh (planar)

So I don’t know how to configurate the quadrangulateMesh to have perfect planar quads ? (does’nt matter if they’re far from initial surface).

Hi Tommy, Really interested by your tool, but I don’t understand where I can find it ?

Sorry for several answers. I’ll try to recap in one.

For AIW, “must choose between maintaining the the corners as points that are actually ON the surface (and losing planarity), or maintaining the planarity and losing the strict location of all corner points on the original surface”

=> I really would like to choose the second option. But I don’t manage to do it.

=> I tried to remove manually these triangles on Sketchup, but it also delete faces, (because i think they’re not planar).

=> I just DL a plugin to import .obj in sketchup, but still the same problem

OK so to recap, my objectif is to have perfect planar quads, but I don’t care if points are far from initial surface geometry and I don’t care if quads are not rectangles. I just want to fix a “maximum” and “minimum” lenght for edges.
For the export problem : If I have perfect planar quads, triangles generated by export are not a problem. I can remove them manually on sketchup and (if initial quads are planar), I’ll recreate the quads faces.

Thanks a lot for all these answers,

Vincent

PanelingTools Plug-in for Rhino 5
http://wiki.mcneel.com/labs/panelingtools

After you install the plugin its a matter of setting up your grid of points based on your form and then panelizing the points.

@tommy (or someone skilled with paneling tools) : Would love to see a step by step on howto achieve this.
Getting quad mesh from Rhino would be a great time saver for me - but I’ve never used paneling tools and so far haven’t felt a need for them (thus I am completely stuck when trying to use them for this purpose).
I know I’ve written that in the past , but damn, good quad mesher inside Rhino would be such a bliss.

Did you look at the paneling tools manual that tommy linked to? It’s pretty detailed and comprehensive. It might seem daunting at first because it covers a lot of capability that you might not be interested in at the moment, but a bit of time spent scanning it and finding the parts you are interested in will surely be time well spent.

Hi Vincent

If you are trying to go cleanly from rhino to sketchup, by far the best way i have found is to open your rhino file in MOI, and export to sketchup from there.
You can also cut and paste between rhino and MOI, which makes the process very easy and fast.
MOI has a great sketchup export.
Rhino - not so good.

cheers
rabbit

I just tried to use “paneling tool”, wich looks really great.

I’ve done a few tests, I manage to do perfect flat quads, with a define “distance” between panels and original grid.

But as you can see, it doesn’t look really “smooth”.

I’ll keep working on, but if someone has an idea of wich parameter i can change…

Thanks,

Vincent

@AIW: to be honest I don’t have time to dig into those manuals - especially considering I don’t need the whole functionality of the package. What I need is to get a quad mesh from Rhino , nothing more .
I know PanellingTools are awesome, but there’s a limited amount of things I could dive in.
If anyone has came across video that shows step by step how to get quads using PanellingTools please post. I think I’ll be able to figure out howto get quad mesh (not quad nurbs patches) from those panels .