I think it means "letting the vanishing point of your visual field go to infinity".

One would not say "making" it go, because it happens more by cessation of action, than by pushing it toward infinity.

visual field / field of vision

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Note added at 26 mins (2011-11-25 15:05:57 GMT)
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Then probably "making" it go to infinity would work.

Dmitri, why do you have doubts about "vanishing point"? This is used in various contexts, with respect to the field of vision.


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Note added at 33 mins (2011-11-25 15:13:12 GMT)
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Literally or metaphorically:

"Perspective, taken in this sense, does not denote the
fixed position of a vanishing point which unifies the field of vision"
http://www.concentric-literature.url.tw/issues/Affect/11.pdf

"Your vanishing point in this case would be very far to the right of the painting. You very seldom, in real life, can introduce the vanishing point into your field of vision, unless your intent is to distort objects for dramatic effect."
http://www.wetcanvas.com/forums/showthread.php?t=623597

"In sum, we have three reasons to say that the vanishing point can be seen: the vanishing point plays a role in optical illusions, it can be precisely located in the visual field through visual means, and it can be blocked from view."
http://artsci.wustl.edu/~rsorense/PAPERS/Vanishing point.pdf