Overview
A big deal of organic modelling workflow spin around good topology of quads (faces with four vertices/edges). Quads allows for many very useful mesh operations, such as selection rings and loops. Quads are predictable which is why they are so useful.
Many applications let you work with non-planar quads. In SketchUp however, it is not so easy. When you modify a vertex of a quad in SketchUp it auto-folds and breaks the quad into two triangles - where as other 3d applications might leave it as one unit.
At the core of every 3d applications, everything consists of triangles - the only difference is how they expose the triangles to the user. However, there is no reason why SketchUp users can't work with non-planar quads - it's just that the tools need to be aware of them.
This toolset is an attempt to begin on such a suite of tools to let SketchUp users work with quads. My approach is conceptually simple: When two faces are separated with a soft edge (smooth only affects shading) then the two faces are treated as one Unit. Click one and you select both and the Entity Info window says you have selected a Surface. Based on that, here is how I define quads in SketchUp:
( QuadFace 0.6+ )
- Native quad face, face with four vertices.
- Two triangles, joined by an edge with the following properties:
- Soft = true
- Smooth = true
- Cast Shadows = false
- Border edges can have any property, just not all of them.
- Faces that makes up a QuadFace cannot have holes in them.
This definition was designed like this because the Hidden property is modified by a model's pages. Each page remembers what entities are hidden or not. When you copy entities from one model to a new one the Hidden property will be lost when you activate any of the existing scenes. This caused problems with the R2 definition which relied on the Hidden property to define the diagonal.
Cast Shadows is a property that is by default on by SketchUp for edges. A diagonal is always an edge that is not visible, it's set to Soft so that the two triangles it separate is treated as one and it's also set to Smooth so the shading blends across the quad. This means a diagonal will never be casting shadows and we can then use the Cast Shadows property, setting it to false, to mark the edge as a diagonal.
This means that bordering edges can be Soft and Smooth as long as they have Cast Shadows set to true. Outlines can then be used on quad face meshes without any artefact which the R1 and R2 used because they relied on Hidden.
( QuadFace 0.4+ )
- Native quad face, face with four vertices.
- Two triangles, joined by a soft + smooth + hidden edge. Border edges can have any property, just not all of them.
- Faces that makes up a QuadFace cannot have holes in them.
( QuadFace 0.1 - 0.3 )
- Native quad face, face with four vertices.
- Two triangles, joined by a soft edge bordered by non-soft edges.
- Faces that makes up a QuadFace cannot have holes in them.
This is just the start of this suite. More will be added progressively. However, I do have some other projects that takes priority at the moment.
Feel free to contribute to the project, but please contact me so I can make sure people are not working on the same thing.
Do not soft the bordering edges of triangulated quads. It is essential that they remain un-soft and that their shared edge is the only one being soft. If you do not want visible edges, hide them. (To ensure a smooth shading, smooth them. Smoothing has no effect on the definition of a quad.) Beware of the different between Soft and Smooth edges!
When you have mesh with hidden & smooth edges instead of soft and smooth edges you will not be able to see an profile of the mesh if you enable Profile edge styles.
Tools that works well with QuadFaces:
http://forums.sketchucation.com/viewtopic.php?f=323&t=28586
Website: Sandbox Tools
The From Scratch tool creates a QuadFace grid of pre-triangulated quads. Perfect start for a quad-mesh.
Convert the Sandbox mesh to QuadFace quads by using Tools > QuadFace Tools > Convert > Sandbox Quads to QuadFace Quads
Website: Vertex Tools
Vertex Tools automatically softens SketchUp's autofolded faces. So if you use it to manipulate a native quad it will ensure that it remains a quad even after it's been auto-folded into triangles. No need to pre-triangulate the quads.
As of 0.4 - when the definition of a quad changed - one need to convert the mesh afterwards by using: Tools > QuadFace Tools > Convert > Sandbox Quads to QuadFace Quads
Future versions of Vertex Tools will preserve QuadFace quads without any post-converting.
A list of related links in regard to quads and topology. Please submit your own links.