3.3. Deformation Visualization

In order to intuitively reflect the deformation of the inner wall of the tunnel on the projected image, the proposed method will visualize the deformation values of the inner wall of the tunnel in three colors: red, green, and blue. Simultaneously, in order to improve the visualization effect, the deformation values will be represented by particular color gradients. This technique is implemented as follows.

First, when the point cloud data are rasterized, the method for interpolating the deformation value is the same as that used to generate the grayscale image (described in Section 3.2). Then, the grayscale value is mapped into the corresponding three channels of red, green, and blue according to the size of the deformation value, and the generated image will display different colors according to the deformation values. However, in order to reflect differences in the amounts of deformation for each case, the grayscale values in each channel are linearly transformed so that the colors in the generated image are displayed with a gradient, thereby improving the visualization effect.