How best to do architectural sections



Architectural sections are typically different from strict planar sections.
There may be no single plane which captures all of the post/brace/window-framing,
roof-to-wall connections
Elements may be aggregated from several parallel planes to generate a
representative composite.

I’ve been monkeying with a completed model and generating a satisfactory section
is proving more challenging than I expected…

Using a section plane eliminates the “foreground” entities OK, but all the “background” stuff is still there.
So I just create a white plane to drop behind the section plane.
There are still lots of both missing and extraneous items.

When doing the floor plans, I resorted to creating FP_ON and FP_OFF layers to put model geometry in
which would be selectively shown/hidden depending on the view one wanted.

Now, adding another orthogonal “layer” of selective hiding has me head-scratching

I am considering creating groups of items which are unrelated except by the need to show/hide them when doing composite sections.
Another tack would be to copy single-instances of all the required geometry to a new location
but that seems kludgey as hell - any model-changes would require changes to the secondary-“section”-model
This is such a standard “thing” that someone must have worked out a simple rigorous effective solution.

In the 2D drafting world, the exclusion/inclusion of geometry was implicitly done on the basis of the particular drawing-view… how to deal with this ?.


[details=General commnet on SketchUp sections …]Any entities collection can have multiple section planes, but each can have only 1 active at a time.
To have multiple section planes active in a view (ie, scene) you must have some of the active section planes inside visible groups or components.

Because it is supposed to still be seen, as a section plane is a viewing plane, just as if you took a knife and cut the building in two along the sectioning plane.[/details]


Its nearly possible! but failed at the final hurdle. Ive tried useing Skalp to do this as you can save a scene for each section, coordinate the camera positions, styles etc through scenes palette, in skalp you can also white out / occlude the background and then layer the views in Layout. The problem is that Layout does not support transparency through the SU views, if it did it use the fog element (as a depth map/ transparency map) it would be relatively simple.


Yes, I comprehend how the section tool works.
(Well, all except for the super bizarro behaviour of throwing up a white shower-curtain in front
of the view any time one edits any components/entities. How can that be by-design ??)

Architectural sections are a deviant form of section.
I am asking how people use the various SU tools/attributes to create architectural sections

The problem is similar to architectural floor plans.
While one could simply do a horizontal section of a model and call it a good floor plan,
a whole whack of stylistic conventions would get clobbered.


[details=Model Info > Components > Fade rest of model …][quote=“kootzie, post:4, topic:44985”]
(Well, all except for the super bizarro behaviour of throwing up a white shower-curtain in front
of the view any time one edits any components/entities. How can that be by-design ??)

It’s by your model settings.

Model Info > Components

See the two “fade” sliders? Move them all the way to “Darker” if you like.[/details]


Sounds like you pounded on it pretty hard, and that it would be a finnicky kludgey process even if it did work…

I’m thinking that it may be easier to simply filter out the occluding/background stuff using groups plus layers or else just layers

My approach of using suitably named layers to manage the FloorPlan vs non-FloorPlan views was
pretty straightforward.
I have a sense that gratuitously grouping stuff just for selective hiding would become brutally painful…


LO does handle transparency if you are in Raster (maybe hybrid) as well? So you can drop a white rectangle, set opacity at 0-whatever percent, and have it work in LO.

But I use multiple windows in LO with a white plane in between. Control stack order by layer. Furthest back is Raster rendered scene, then the white out rectangle, then the vector rendered cut only, on its own layer and scene, as generated by section cut face.

For structural details I usually build detailed models showing how it all comes together.

Structural plan view - colored lines for structural elements added in LO with notes, the timber is in one viewport with only the timber turned on, this is sitting atop the normal plan view below.


And here is an example of laying the timber components in a window on top of the general building view so people can easily understand how the structural system works with the overall house.


To control what you see, I use layers in my SU models - Exterior Walls, Interior Walls, Entourage, Furniture, Etc. all existing on layers, so I can tune visibility per view. This makes adding people (on my A-ENT layer) work in section or elevation view - but not in plan (where they don’t show up correctly.

I’ve purged that list - but:

A layers are ‘Architectural’ (A-F-0=lower level, A-F-1=main floor, etc.).

S- are for my section / plan cuts.

WO are white out planes for ghosting or obscuring. I- are for interiors - stuff that I might not need on certain sheets - furniture, etc.

I also have a bunch of X layers I usually purge out when I get to construction documentation stage - references / sketches / old geometry I might want to keep around, etc.


wow. thats pretty fantastic. I like that. alot

this is the sort of thing I have been trying to achieve - I haven’t been able to get it to work in hybrid. I hadn’t though of of stacking using different render modes and a sheet of ‘tracing paper’ in between


It’s way simpler than you think if you just consider using a section group.

You’ll need:
1 - A section plane;
2 - A layer for that section;
3 - A scene for that section with the view aligned with that section plane.
4 - A new geometric group that is created from the intersection of the section and your model’s geometry which you insert in the layer of the section.

Skalp does that dynamically and automatically. People seem to love it.

I use SectionCutFace plugin for #4 and Supersection for setting up #2 and #3 as I like my Section Groups to be static so I can draw details and draw faces that hide what I want inside the group.


Weird!! I could swear there was a section-plane-dependant fading of the edited component when viewed through the section plane, but now, I can’t replicate it.


You’ll have to take a second look. That fading should be of a section plane. It’s a grey transparent face. Usually you don’t want to see that fading as it interferes with all the model.

Fade rest of model is a modelling help but not useful for detail.

As mentioned already you want to use fog for that, but it will only work in Raster mode. No Vector or hybrid mode in Layout and no export to dwg.

If you want to hide away parts of your model, the best way is to draw geometry inside the section group.


Thanks bmike for sharing your screen,


I do not understand the need of set your #2, can you explain the benefit of it?

I’ve been doing my Layout section with SketchUp scene without ever assigning the section plane to its own layer.

I’ll appreciate it.


In my workflow having the actual geometry of the cut (along with the ghosted section plane) on its own layer means I can stack views, isolate that geometry, and makes drawing organization and workflow much smoother.


What @bmike said.

I often have 20+ sections per project. If you view them all at the same time, it’s a mess. Having a layer and scene per section allows me to focus on a single section at a given moment, isolating it from the others that would, otherwise, be scattered all over the place.

That layer can also hold geometry like the section cut grouped geometry. This can be geometry that exists only to facilitate the reading of that particular section, which is your particular case. This can, however be other kind of geometry. I use it, for instance, to draw details in section cut face groups:


I do have the geometry of the section (created with SectionCutFace) on its own layer, but no the section plane.

My Layout section plan inluded stack views from 3 to 4 SketchUp scenes, but I do not have the section plane on its own layer, but I would like to understand the benefice to have the section plane on its own layer.


PS. I posted the above before reading JQL answer, now I know why is better to have each section plane on its own layer.

Tanks bmike & JQL


As bmike has suggested above, why not generate a separate model that you can cut a section through to give you the appropriate view.

However, from the perspective of a long time Civil/Structural draughtsman, I really do question the wisdom of generating the composite sections you’re referring to.

I say that because I frequently find myself in a situation where Engineers or local Councils cannot follow, what I consider to be a basic 2D detail, and require a 3D representation of the detail. That’s where Sketchup comes in to it’s own, and why I love it so much … :smiley:


In these cases I sketch in a physical paper with a physical pen. They will eventually get there and finally understand all the drawings, 3d models, physical models, renders, descriptive texts and all the amount of useless data they force us to create so they can clearly understand our projects… The more they force us to document, the less they have the time to see and the less they understand. In the end all that effort makes you return to the basics so they can get a hold of the base idea.

Nonsense if you ask me…


Nonsense you say. Unfortunately, I have to agree with you, and I say unfortunately because the ability to read a set of construction drawings seems to be a dying art …