Volume rending representations of the ¹³CO(1–0) emission and the corresponding G-virial map. The upper panel shows the result from the Perseus molecular cloud and the lower panel shows the result from the Ophiuchus molecular cloud. Blue stands for ¹³CO(1–0) emission and red and orange stand for G-virial. Both clouds are projected along the velocity direction. For the Perseus molecular cloud, the iso-surfaces of ¹³CO(1–0) emission start from 0.3 K and increase in steps of 0.64 K. The contours of the G-virial starts from 1.2 and increase in steps of 0.8. For the Ophiuchus molecular cloud, the contours of ¹³CO(1–0) emission start from 0.3 K and increase in steps of 1.24 K. The contours of the G-virial starts from 1.2 and increase in steps of 0.8.