Reading a 3D model without CAD experience: what you need on the shop floor

Someone puts a tablet in your hands. It has a 3D model on it of the project you are currently working on, and the idea is that you get on with it yourself. You have been reading drawings for years, so that is not the problem: a dimension line, a section, a scale, you grew up with those. What feels strange here is something else.

The image turns. You swipe with a finger and the whole building tilts with it, and after a few movements you no longer know which side you are looking at. On paper, up was always up, and the facade with the gate was always on the left. On a screen that is not fixed, and it is exactly that loose quality that can leave someone with years of drawing experience searching for a moment.

That is easy to fix, and it does not take a course. What follows is the handful of words and habits you need to find your way around a model, without anyone having to explain what a beam or a wall is.

The handful of words you need

A model uses a handful of terms that you pick up quickly because they connect to what you already know. An element is the part you can tap: a wall, a beam, a pipe, a door. A model is built up from those elements, not from separate lines like a drawing. Where a drawing shows a line, a model shows the thing itself.

A layer or group is a set that you switch on or off in one go, for example the structure, the services or the finishes. A view is where you are looking from: from above, from the front, or in perspective. A section cuts through the model virtually so you can see inside, just as a section on a drawing does, except you choose where it falls. And a version is the model’s state when the drawing office published it. That is all the jargon you need on the shop floor.

Orientating without getting lost

Rotating, panning and zooming all work with two fingers, and you pick that up within a few minutes. The most important habit does not come naturally: find the button straight away that resets you to a fixed view. In most viewers it sits in a corner of the screen, often shown as a little house or a cube, and whatever it looks like, it always returns the model to a position you recognise. That way you can always find your way back, whatever you turned.

Also pick a landmark before you start turning the model: the facade with the gate, the stairwell, the storey you are currently working on. As long as you keep that point in mind, you still know where you are even after a few turns. Someone who gets lost in a model is usually not lost because of the turning itself, but because they zoomed in on something and lost track of where it sits in the whole. Zoom back out first, then, before you keep searching. What that button bar looks like on the shop floor is described under the viewer controls.

Tapping and layers: seeing what is underneath

Tap an element and you see what it is and which properties the draughtsman gave it, such as material, dimension or type. Switch off the finishes layer and you suddenly see the studwork or the pipework behind it, without having to look for a separate drawing.

What you switch off is not gone. You are only hiding it from yourself for now, and as soon as you tick the layer back on, everything is there again. No tap breaks anything: a viewer lets you look, not change. For a lot of people that worry disappears the moment someone tells them once and they try it themselves.

What a dimension in a model does and does not mean

A dimension you look up in a model is the dimension as it was drawn, not necessarily as it is built. There is play on the shop floor, and there is a difference between a shell dimension and a finished dimension. For a routine check, what the model shows you is enough. For a critical connection, where a few millimetres make the difference, the tape measure is still the instrument you fall back on.

What the draughtsman has not drawn, you cannot measure in a model either, however sharp and polished the image looks. A dimension you measure yourself between two points in the model is also different from a dimension line on a drawing: the draughtsman placed that deliberately, from a reference point they chose, while yours falls between two arbitrary points. Both are useful, but it helps to know the difference before you base a decision on it.

Why version is the word that matters

A model that looks polished and current can just as easily be last month’s state. The screen shows no rust and no dust, so you cannot tell from the model itself whether it is out of date, as you sometimes could from a yellowed printout. So look for where on the screen it shows which version you are looking at and when it was downloaded. Most viewers show that at the top or in a side panel, usually in small type.

If you are unsure about something that cannot be undone, a cut you are about to make or a pour you are about to start, call anyway. A viewer does not replace the conversation with the drawing office, it makes it shorter and more focused, because you can say exactly which element and which version you are looking at.

No training, just a few agreements

Ten minutes at the workstation is usually enough to get someone started, because the controls themselves are not the hard part. What needs to be agreed beforehand matters more. Someone sets up the layers and the starting view for a particular workstation, so nobody starts from scratch every morning. There is a known name for who you go to when you see something in the model that is not right. And the agreement that is missing most often: asking a question is cheaper than guessing, even if work stops for a moment.

Every trade also looks at the same model with its own eye. What is a detail that barely matters to one team is, for another, exactly the element everything turns on. What each trade needs on its screen differs from trade to trade, so it is worth agreeing this per team. Once those agreements are in place, reading a model comes down to little more than what you have already done with a drawing for years: look, measure where it is needed and get on with the work.