ov_cmat_apply: Apply the camera matrix to 3D coordinates

In openvolley/ovideo: Volleyball Video Utilities

Apply the camera matrix to 3D coordinates

Description

The camera matrix characterizes the mapping of a camera from 3D real-world coordinates to 2D coordinates in an image.

Usage

ov_cmat_apply(C, X)

Arguments

C	: camera matrix as returned by ov_cmat_estimate(), or the coefficients from that object
X	matrix or data.frame: Nx3 matrix of 3D real-world coordinates

Value

An Nx2 matrix of image coordinates

References

https://en.wikipedia.org/wiki/Camera_matrix. For general background see e.g. Ballard DH, Brown CM (1982) Computer Vision. Prentice-Hall, New Jersey

See Also

ov_cmat_estimate()

Examples

## define real-world and corresponding image coordinates
xX <- dplyr::tribble(~image_x, ~image_y, ~court_x, ~court_y,   ~z,
                        0.054,    0.023,      0.5,      0.5,    0, ## near left baseline
                        0.951,    0.025,      3.5,      0.5,    0, ## near right baseline
                        0.752,    0.519,      3.5,      6.5,    0, ## far right baseline
                        0.288,    0.519,      0.5,      6.5,    0, ## far left baseline
                        0.199,    0.644,      0.5,      3.5, 2.43, ## left net top
                        0.208,    0.349,      0.5,      3.5, 0.00, ## left net floor
                        0.825,    0.644,      3.5,      3.5, 2.43, ## right net top
                        0.821,    0.349,      3.5,      3.5, 0.00) ## right net floor

C <- ov_cmat_estimate(X = xX[, 3:5], x = xX[, 1:2])

## fitted image coordinates using C
ov_cmat_apply(C, X = xX[, 3:5])

## compare to actual image positions
xX[, 1:2]

openvolley/ovideo documentation built on March 19, 2024, 9:52 p.m.