fix definition in function pytorch3d.renderer.cameras.look_at_view_transform (#120)

Summary:
fix Args' definition at line 1016, 1018, 1020 in function pytorch3d.renderer.cameras.look_at_view_transform.
Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/120

Reviewed By: bottler

Differential Revision: D20597565

Pulled By: nikhilaravi

fbshipit-source-id: e10a221e3dccc0adf20b26808ad67328408a4388

pytorch3d/renderer/cameras.py

@@ -939,11 +939,11 @@ def look_at_view_transform(
     Args:
         dist: distance of the camera from the object
         elev: angle in degres or radians. This is the angle between the
-            vector from the object to the camera, and the horizonal plane.
+            vector from the object to the camera, and the horizontal plane y = 0 (xz-plane).
         azim: angle in degrees or radians. The vector from the object to
-            the camera is projected onto a horizontal plane y = z = 0.
+            the camera is projected onto a horizontal plane y = 0.
             azim is the angle between the projected vector and a
-            reference vector at (1, 0, 0) on the reference plane.
+            reference vector at (1, 0, 0) on the reference plane (the horizontal plane).
         dist, elem and azim can be of shape (1), (N).
         degrees: boolean flag to indicate if the elevation and azimuth
             angles are specified in degrees or radians.