Simplified alternative to Dynamic Component Railing for use in large SU models

As regular forum participants may know, I’ve been working with Scott Baker (@NewThinking2) on a very large and complex SU model. To give you an idea of scale, it is currently (in round numbers) about 270MB, has 27 million edges, over 11 million faces, 560,000 component instances, 5,500 component definitions, and 60,000 groups (mostly imported 3D warehouse models - they could probably usefully be converted to components).

One particularly resource hungry type of component is a Dynamic Component Railing. It is widely used in the model tor terrace railings, of which there are several hundred sets, some quite long with many vertical spindles. This adds dramatically to the edge count, and can drastically slow down not only modelling, but even viewing when you try to orbit or zoom, once SU has too many to deal with.

Here’s a typical example:

In typical DC fashion, you use the Scale tool to adjust the length, and the number of spindles adjusts to fit, keeping a constant spacing:
DC Railing

I wanted to create a much simpler component, to avoid both the high number of edges in the full ‘solid’ railing, and the per-component overhead of a DC which seems to be about 5KB.

So I have devised a simpler structure, one version with and the other without corner posts.

They use a small image of the spindle as a repeating element in a texture applied to a face between top and bottom rails and the posts, or blank ends for the short cross railings.

This is made from a screenshot of a solid railing (image on the left), saved as a PNG file, and modified to have a transparent background (image on the right)using Preview/Instant Alpha on a Mac, or some equivalent image editor on Windows.

I then imported this image as a texture, and applied it to a face in the simplified railing component, which is loose geometry inside a single-level component.

Turn on View Hidden Geometry to make the edges of the face visible, and able to be acted upon by the Move tool, and you have a lightweight component which behaves much like a DC. To change the length, window select round the end post and the end of the face with the textured image, and Move along the axis.
Imaged Railing

Even close up, from the right viewing angle, it’s hard to tell the difference between the simplified and the original versions


And here’s the SKP file (saved back to v8):
[EDIT] I forgot to purge the file uploaded earlier - here’s the purged and MUCH smaller version - just 53KB.
Terrace railings - imaged.skp (52.9 KB)

The equivalent 3-railing set of DC railings is about 290KB.

The DC railing set has (again, in round numbers) 1600 edges, 800 faces, and 130 component definitions (of which, most are copies of the spindle, but separate definitions, not just instances).

The imaged version has fewer than 160 edges, 70 faces, 3 component instances and 2 definitions (two types of railing, one with, and one without, corner posts).

At a distance, the imaged version doesn’t appear so ‘heavy’ visually (even with Profile edges turned off, the DC goes almost black as the ‘real’ edges merge when you zoom out).

The windows too are a simplified version - done again mainly to reduce edge count from all the verticals. That’ll be the subject of a separate post. There are two images to give the illusion of depth as you orbit.


Replacing geometry with textures almost always pays in terms of performance. Difficulties arise only when the model has to be exported to other formats or viewed in hidden line mode.

For just that reason, we are keeping copies of the solid terrace railings as well, but on a separate layer for each type, with the solid ones normally turned off.

I never have a model that big because I like to break my models in pieces like I would do in Autocad.
for example… I divide always: Site, Landscape, Sitework, Building …if the building is getting complex I divide it even more: Exterior Glazing and Doors, Interior doors…and maybe sometimes Build-ins.


  • Easy to handle so I can add more detail per piece
  • Easy to work in team ( I use cross reference organizer) so I know if I do need to update one of the files
  • I can link or unlink the piece that I need temporarily.
  • If for any reason crash or the file is corrupted I don’t lose everything

And because of everything above I work way faster and my computer is running smoothly most of the time.

My models are well-detailed way more than I can see there and with textures and never had any problem,

We have it partially divided into sub-models and I can and often do work on one of more of those separately from Scott, but he needs to be able to see most of it to judge how to handle the complex interactions between different parts of the building. The geometry is unusual and challenging.

And things have had to be reworked more than once, when a design decision carried on up the building proves not to work well, and lower floors then have to be revised.

It’s becoming both more modularised, and better structured, so we are (just) containing the complexity and model size as it grows. We’ve made a number of simplifications, which have reduced the model size from what it would have become, which would otherwise have made it unworkable long ago.

What you see in the images here is a very small fraction of the whole building, and only the exterior. There’s a lot more going on inside, too.

John to me there is not another way around to divide the model into pieces, components as much as possible and I do have a master model where I put everything together… If I’m working on the exterior glazing I import the shell of the building via “cross reference organizer” … that extension tells me if one of my pieces have been updated so I can reload it.
I purge my models as well very often because I have the model in pieces and set up the auto backup every 1hr or more and sometimes I turn it off…I found SU crashes most of the time when is autosaving and you are in the middle of something.

I add a lot of detail to my models because I use them for construction documents as well as Renderings in 3ds Max+Vray… I use two sizes of maps, one for SU at (1024px maximum) and the high resolution for 3ds.

Regarding the railing, it’s very simple so I don’t see why you should simplify them even more…probably your problem is memory and video card… I work with 32GB RAM and 8GB video card on a laptop combined with the workflow that I use I didn’t have major problems handling models.

If you want I can take a look at your model.


every little thing counts… I would turn off profile under styles…I use a style for modelling … Very simple one without any fancy feature

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