DIC Tool

The DIC Tool is available as a tool in the PreProcessor and may be used to manually (and visually) optimize the mesh between to images. The two images has first to be loaded into the two views (View1 and View2) of the PreProcessor.

Often, this tool is used to optimize the mesh between two cameras (as needed in 3D-DIC), and often a coarse fit is first found using the Mesh Extender Tool.

• To open: In the PreProcessor menubar click Tools ⟶ DIC

This toolbox contains two main functionalities, separated in two panels, i.e. FFT Filter and DIC

FFT Filter

Using this option it is possible to apply a low-pass filter on the underlying images in both views of the PreProcessor. This low-pass filtering of the underlying images, allows the DIC optimization to search for its global minima in a larger region of the image. Thus, it is possible to optimize the mesh even though the nodes are relatively far from its optimal position. It is typically required when trying to match the mesh between images coming from two different cameras.

A 2D FFT algorithm is used to convert the images to frequency domain. A mask is applied, removing the high-frequency components of the image before an inverse FFT alorithm transforms the image back to its original domain. The resulting image will then be a low-pass filtered version of the original image.

The FFT Size has to be power-of-two. It is possible to choose between 1024 and 2048. The default value of 1024 is sufficient for most cases.

Note

Apply the low-pass filter to the images in the two views by first checking the Use FFT checkbox. Then apply an integer number between 1 and 500 in the Mask Size textbox and press Enter. The filtered version of the images should then be visualized in the two views of the PreProcessor.

The Mask Size is defining how much of the low-frequency components to preserve in the filtered version. Thus, a mask size of 1 means that almost all information in the image is filtered out. A mask size of 500 on the other hand will look very much like the original image as most frequency components are preserved. Note that the maximum Mask Size is half of the FFT Size.

Hint

Typically the mask size may be varied between 10 and 300 in the process of matching a mesh between two cameras.

Note

To turn off FFT filtering, uncheck the Use FFT checkbox.

DIC

Here, the mesh may be optimized between two views, typically from View1 to View2. The FFT Filter (as described above) may be used to increase the incremental steps allowed in the optimization, typically if the nodes are far from their optimal positions.