Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Let's say we're transforming a square to an arbitrary 4 points via projective transform.
Is there a way to ensure that the resulting points have homogeneous coordinates that are >0 ? i.e. sending the square (0,0),(1,0),(1,1),(0,1) to (x1,y1,w1),(x2y2,w2),(x3,y3,w3),(x4,y4,w4) -- it is sometimes useful to use w<0 as an indicator that the point is behind a clipping plane attached to a virtual camera.

a matrix may be of the form found here: these are 2d image warps, but may produce homog. points with w<0;

thank you!

share|cite|improve this question

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.