I classified laying logs (tree trunks) from CHM (Canopy Height Model = Digital Surface Model (DSM) - Digital Terrain Model (DTM)) created from LiDAR point cloud. I converted classified logs into polygon shapefile. I now have polygons that represent logs and CHM image. CHM were clipped by polygons (logs), now I am thinking of calculating volume of each log using QGIS. Is there any existing method?