# Differences

This shows you the differences between two versions of the page.

 tutorials:graphics:opengl:quaternion [2019/08/20 14:51]alanzheng created tutorials:graphics:opengl:quaternion [2019/08/20 14:53] (current)alanzheng [Reading quaternion] 2019/08/20 14:53 alanzheng [Reading quaternion] 2019/08/20 14:51 alanzheng created 2019/08/20 14:53 alanzheng [Reading quaternion] 2019/08/20 14:51 alanzheng created Line 23: Line 23: ==== Reading quaternion ==== ==== Reading quaternion ==== - This format is definitely less intuitive than Euler angles, but it’s still readable: the xyz components match roughly the rotation axis, and w is the acos of the rotation angle (divided by 2). For instance, imagine that you see the following values in the debugger: [ 0.7 0 0 0.7 ]. x=0.7, it’s bigger than y and z, so you know it’s mostly a rotation around the X axis; and 2*acos(0.7) = 1.59 radians, so it’s a rotation of 90°. + The xyz components match roughly the rotation axis, and w is the acos of the rotation angle (divided by 2). For instance, imagine that you see the following values in the debugger: [ 0.7 0 0 0.7 ]. x=0.7, it’s bigger than y and z, so you know it’s mostly a rotation around the X axis; and 2*acos(0.7) = 1.59 radians, so it’s a rotation of 90°. Similarly, [0 0 0 1] (w=1) means that angle = 2*acos(1) = 0, so this is a unit quaternion, which makes no rotation at all. Similarly, [0 0 0 1] (w=1) means that angle = 2*acos(1) = 0, so this is a unit quaternion, which makes no rotation at all. refer to: http://​www.opengl-tutorial.org/​intermediate-tutorials/​tutorial-17-quaternions/​ refer to: http://​www.opengl-tutorial.org/​intermediate-tutorials/​tutorial-17-quaternions/​