How to build lookup table for inverse perspective mapping?

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Here's what I have: http://img21.imageshack.us/img21/9017/imag1160p.jpg

Right now I'm using warpPerspective() to generate the birds eye view (inverse perspective map) but it's really slow.. I've been reading in some papers that you can build a lookup table and use that to map the points. ( for example here: http://shanetuohy.com/fyp/Images/Shane%20Tuohy%20Thesis.pdf >> @ page 23 >> 5.1 Generate lookup array

I would say, give it a go. I haven't done anything related in the area so can't help ya for the moment :)

razvan i'm trying to implement inverse perspective mapping in image of road for calculate the distance but i can't generate bird-eye view :( how do you calculate destination points?

I did it by hand, manually, on a sheet of paper.. Basically on the src array you have 4 points in a trapezoid shape. On the dst array you put the corresponding calculated 4 points that represent a sqare/rectangle. I tried multiple values for the dst array, until I got a good result. Using the data from the calibration tutorial (extrinsic parameters w/ rotation and translation vectors) didn't work as expected. The source code for the transformation matrix is written in my initial question (the "m" matrix). After that you apply:

 Imgproc.warpPerspective(mRgba, tempMat, m, ddsize, Imgproc.INTER_LINEAR | Imgproc.CV_WARP_FILL_OUTLIERS);

 mRgba = tempMat.clone();