Animating 3D object using Mask layer - Page 2

Step 2

Create a new layer. With the line tool and the shift key depressed (this will constrain the angle to 45 degrees) draw a line from the vanishing point to the lower left corner of the page. Repeat this step but this time draw to the lower right corner. Extend the created lines beyond the page boundaries and now intersect the two lines with another one outside of the movie borders. Select the paint bucket and fill the created triangle. This determines our field of view. Later this layer will be a mask but for now just name it Mask and lock it.
See picture: