Changing colours in sections

I am interested to find out how others deal with this problem.

When doing alteration work on buildings, you often want to distinguish elements that are to be retained, those that are to be removed, and the new. For clarity, it is nice to use different colours.

Let us say that we want to do this for walls and that they are constructed such that they sit on the surface of a floor. To create a floor plan, you are likely to use a section cut.

By default, without Section Fill, you should see the default back colour. You can change this easily enough. But you will get Z fighting with the floor and the colour may not show up.

One workaround would be to create a “ghost” horizontal element somewhere above floor level, hiding the lines that define it and leaving just a surface. It works but it is somewhat messy as a solution. But you do get what you want like this:

Any other neat ideas?

I would use TIG’s Section Cut Face to create actual faces at the section cut so they can have different materials applied to them. I used that with some different hatch patterns for the section view of the spark plug I modeled recently. It could just as easily have been different colors.

Same thing with colors in the model of a steam engine.


I usually trace over in Layout Simon.

Or sometimes if it’s, say, an extension off the rear or side elevation, I’ll resize the viewport back to the existing wall elevation and then create a separate viewport for the extension using a different style.

Dave’s solution is one I often use. Another method would be to use tags and stack scenes in LayOut using different styles for the different tags.

Using TIG’s extension in a section that is contained within a group allows you to colour it individually. You can then just change the back face default colour for everything else and switch off Section Fill. It can leave various lines showing within the open section cut but it’s probably good enough. You do have to watch out if you move the group section cut as the coloured face doesn’t move with it automatically.

I can see that the other solutions would work too. So, thanks to all for suggestions.

That’s not right. You can set the section cut face to automatically update when you move the section cut.

Or update on demand.


Wow that’s something I wish I knew about a long time ago…very helpful!
How did I miss that?

(oh yeah…i dont read sketchucation very often)

Let me open a proverbial can o’ worms…

How about NOT using Section cuts to create floor plans?

Why would you do that?

  1. not dealing with section planes
  2. colours and patterns for walls, without having to explode or model extra bits in LO or SKP.
  3. ablility to create floor plans from floors that have elements that dont line up on a horizontal plane, eg:

This applies to Demo plans and “wall type” plans.

Have a look at the following SKP 2021 file:

Demolition Plan Example.skp (131.0 KB)

I presume the house in the screenshot has a single split level floor? How do you go about showing the lower floor when you also have upper floors?

Also, your demo building is not doesn’t have full 3D detailing. Your windows wouldn’t show in elevation and you have instead chosen to use a 2D element to represent them on plan. It’s fair enough, but not everyone would want to model in that way.

I must have missed a setting then. When I tried doing that, the cut face got left behind. Better try harder!

It doesn’t hurt to read and poke at the UI in the various plugins and extensions out there.

Screenshot - 7_4_2021 , 5_52_43 AM

…Not quite sure what you mean about not being in 3d - the windows are in the model, in 3d ,and show in the Elevation scene. I just used simple windows, but you coudl make them as detailed as you like or apply the tecnique to any object (furniiture, plants, etc).
The same technique (2d and 3d versions) can be applied to all furniture, fittings, etc (not just windows).

Do you mind posting your example SKP file? Im just curious to see how it’s set up.

In any multi level home I create differnet levels or structures, each a seperate component.
One of the problems I wanted to overcome was that of generating a (simplified) 2d floor plan (per level) without the use of multiple section planes per level.
I notice your floor plan appears to be a literal slice through 3d geomtery, but I needed to adapt my workflow to scale up to projects involving drawing scales as high as 1:1000. That’s where symbolic 2d compoments (including widows, furniture, electrical fittings,etc) are essential.
Simple 2d elements are also very fast to render in LayOut, and can still be legibile at scales up to 1:1000.
My 2d/3d approach is also designed to adhere to my local building regulations, which require basic plans that look like this.. The detailed views (explaining structure or construction methdology) are isolated exploded or zoomed in perspective diagrams, not necessarily connected to the main 3d model.

I’ve personally never enjoyed managing numerous section planes…some models can have over 100, and it just gets too much. 100 tags, 100 scenes, 30 styles, 100 section planes…then LO tag/style/view adjustments…yikes.

I acknowledge that this “hollow wall” technique is not for everone, but it does acheive your request of being able to colour the different walls in unique colours/materials without having to create seperate geometry :slight_smile:
I always find it educational to see what other professionals are producing with SU+LO.

Me too. Hence the OP.

I guess there are many different ways to do this. One alternative to using sections would be to generate 2D plans using Create Group from Slice and then colouring those appropriately. But then it wouldn’t update automatically with subsequent changes. Also, I have developed a system now that has a single model to cover all aspects including before and after. It’s a lot neater than having an existing and a proposed as in the old days.

You seem to be in NZ and I am in the UK. I suspect the requirements for standard architectural representation involving 2D plans, elevations, and sections, may be very similar. Certainly, your indicative plan looks just like ones I am familiar with.

I am glad to say that I never have anything like 100 section planes. On the kinds and sizes of buildings I work on, I rarely need even double figures. So maybe that makes a difference to how it is best to work.

I will PM you with the drawing.

Thanks - I see that’s a good workaround…particularly useful with stairs.

Do you model upper and lower levels of a building in seperate components?
I do that anyway because it makes it easier to lay things out, furniture, interiors, etc.

And do you model windows and other similar elements always in 3d, but with two levels of detail (on seperate tags?) so when you do sections you are likely to turn off some of the 3d window hardware, glass and other stuff?

Our industry spec is here:

Standard details usually come from a library (sometimes manufacturer-supplied) and we dont tend to do a lot of CDs beyond that.


When I am working in 3D, I do model windows and doors. I don’t need 2D elements for the windows as my sections cut through the 3D models of them. Doors are different because I like to show them closed in elevations and open in plans. I guess I could have two models of the same door in 3D (open and closed), but I actually use 2D elements in plans (as you seem to do).

No, see above.

We don’t have anything like that in the UK but I can see its usefulness in new build, especially for organisations like housebuilders. Because so much of our housing stock is very old, off the peg solutions don’t work so well.

Simon, if you have a 2D element for your windows you can make use of the tag override ability in Layout to have windows in a different line weight.

Because of some of the issues to do with tag override that I have mentioned in other posts there are some situations where the override for some structural opening configurations produces undesirable results but for for me I have developed a workaround for these situations and it works well for me.

For all standard rectangular structural openings using tag override behaves as I expect it to.

Paul, I will investigate your lineweight suggestion. However, I have started to wonder whether it is either necessary or desirable to have 2D elements in a 3D model. I don’t need them for windows but I do use them for doors showing on plan. However, it is possible to have a door component that contains both the open and closed version and to use tags in scenes to control visibility. The only fly in that ointment is the door swing. I don’t see how to overcome that anomaly.

Here is an example:

762 flush door open_closed.skp (178.6 KB)

Your tags are so organised Simon :exploding_head:

Shucks - forgot to purge…

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I do too, but end up with various door groups, some open, some closed. For a walk through or presentation views, closet doors are closed and room doors are open. Some exterior doors are closed, while others like to outdoor decks are open.
Screen Shot 2021-07-05 at 3.14.18 PM