Surface Deflection Analysis

Easily visualise deflection and accurately measure planes on any surface.

Josh Sinclair avatar
Written by Josh Sinclair
Updated over a week ago

Video Overview (6 min)

Roof Deflection Analysis

Trendspek 2.0 has simplified the process of producing a roof deflection visualisation

1. Outline the Roof Plane

Begin by right clicking on the corner of the roof and click start drawing to draw a polygon of the rooftop.

💡 Place your first and second points so that the line between them is on top of a load-bearing structure or the peak of the roof.

You want to identify and outline a single plane of the roof as shown below.

Style it accordingly → typically neutral colours for the roof deflection visualisation work best, just so the colour of the polygon doesn't conflict with the visualisation.

2. Change to Roof Deflection

Before we click create to turn this into an annotation, we are going to click on the polygon drop down and convert it into a Roof Deflection.

3. Choose Plane Type

There are two algorithms that can be used when identifying the surface of the plane that the visualisation will be produced against:

  • Average

  • Fixed

Average Plane

Average uses tens of thousands of points to create a plane that represents the roof's surface, producing a visualisation of high and low spots above and below the plane.

Average is best used for deflection visualisation on large concrete slabs or similar surfaces.

With a roof, we find that the fixed plane is more suitable – especially if you have some knowledge of the underlying roof structure.

Fixed Plane

Fixed fits a plane that coincides with the first two points of your polygon, then pivots the plane down to best match the remaining points.

Here, you need to be careful with the position and ordering of the points as you're drawing the polygon on the roof so that the algorithm can calculate the deflection accurately.

This is why its important to place your first and second points so that the line between them is on top of a load-bearing structure or the peak of the roof. This method produces a visualisation more consistent with what our users are expecting.

4. Choose Accuracy Type

  • Normal

  • Precise


Normal accuracy evaluates what's currently on your screen. In most cases, normal mode is more than adequate.

To get the best results, position the 3D model so that the roof section that you're visualising fills the entire screen you’re working on.


Precise accuracy will request the highest possible level of accuracy from the 3D model from Trendspek servers.

This mode takes a lot longer because it can potentially require thousands of files to be loaded from Trendspek.

5. Generate your Roof Deflection Analysis

Once you’ve selected your plane and accuracy, click create.

Trendspek will analyse thousands of points across the roof to produce the visualisation. Be patient, this does take a few seconds and, or if you used the precision accuracy, potentially minutes, depending on your internet connection.

6. Analyse your Roof Deflection

Once you’ve generated your analysis, click on the drawing tab. Here you can tweak your visualisation to suit your reporting requirements.

Hover over the visualisation to see the deflection measurement from that plane you produced. This allows you to identify low spots within a surface such as a roof.

Please contact [email protected] if you have any questions or feedback.

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