The Deviation Tool is used to analyze the distance between two Mesh objects. The tool will highlight areas where the distance between the meshes is larger than the Max Deviation setting in the property panel, shown to the right. An example is shown below.
By default, measurements are only taken from the first selected object to the second selected object. This is usually sufficient if the meshes on each object have similar sampling rates. However you can get a more precise result by checking the Bi-Directional box, which tells the Deviation tool to compute distances in both directions. This does take additional computational time.
The image below shows two slightly different bunny meshes in the left two images. Then we show the result of the Deviation tool at 0.5mm and 0.25mm. Areas that are close to the Max Deviation are highlighted in yellow, increasing to red as the deviation reaches the threshold. Above the threshold, the triangles are colored dark red with a boundary highlight, and a stick-ball marker identifies each separate region. You can left-click on the ball associated with a region to automatically start the Select Tool with these triangles selected.