[feat] Create a filter to compute pointcloud volume

Goal

This MR creates a filter to compute the volume of a space formed by an input pointcloud and a plane.

The volume is estimated by doing integral of areas formed by scanlines and the plane.

Input

• a pointcloud
• a plane

Output

• Rasterized pointcloud w.r.t input plane
• Rasterized pointcloud display in xy plane direction
• The estimated volume

Method

• Step 1: Get the input pointcloud and the plane.

  The plane is used to defined which part of volume would be calculated:

• Step 2: Rasterize pointcloud into a 2D grid.

  The resolution is defined by Raster resolution. To simplify the calculate, we rotate input points onto XY-plan. So, the x, y coordinates of a points is used to place the point into the grid. Then we keep one point who has the max value of z in each bin of grid.

• Step 3: Compute integral volume.

  To compute volume, we compute the area of each column of grid by following the scan direction. The we integrate the column areas as the estimated volume.

Parameters

• [double] Grid resolution: the size of a raster bin. The raster size depends on the pointcloud size and the raster resolution.
• [enum] Scan direction: direction of the integral.