get_line_of

Herror ::get_line_of_sight ( const HTuple &Row, const HTuple &Column, const HTuple &CamParam, HTuple *PX, HTuple *PY, HTuple *PZ, HTuple *QX, HTuple *QY, HTuple *QZ )

Compute the line of sight corresponding to a point in the image.

::get_line_of_sight computes the line of sight corresponding to a pixel (Row, Column) in the image plane. The line of sight is a (straight) line in the camera coordinate system, which is described by two points (PX,PY,PZ) and (QX,QY,QZ) on the line. A pinhole or telecentric camera model with radial distortions described by the internal camera parameters CamParam is used (see ::camera_calibration). If a pinhole camera is used, the second point lies on the focal plane, i.e., the output parameter QZ is equivalent to the focal length of the camera. The equation of the line of sight is given by

  |X|   |Px|       |Qx-Px|
  |Y| = |Py| + t * |Qy-Py| .
  |Z|   |Pz|       |Qz-Pz|

The advantage of representing the line of sight as two points is that with this, it is easier to transform the line in 3D. To do so, all that is necessary is to apply the operator ::affine_trans_point_3d to the two points.

Parameters

`Row` (input_control)	real-array `->` HTuple.double
Row coordinate of the pixel.

`Column` (input_control)	real-array `->` HTuple.double
Column coordinate of the pixel.

`CamParam` (input_control)	number-array `->` HTuple.double / long
Internal camera parameters.
Number of elements: 8

`PX` (output_control)	real-array `->` HTuple.double *
X coordinate of the first point on the line of sight

`PY` (output_control)	real-array `->` HTuple.double *
Y coordinate of the first point on the line of sight

`PZ` (output_control)	real-array `->` HTuple.double *
Z coordinate of the first point on the line of sight

`QX` (output_control)	real-array `->` HTuple.double *
X coordinate of the second point on the line of sight

`QY` (output_control)	real-array `->` HTuple.double *
Y coordinate of the second point on the line of sight

`QZ` (output_control)	real-array `->` HTuple.double *
Z coordinate of the second point on the line of sight

Example

HTuple CamParam,Row,Column,PX,PY,PZ,QX,QY,QZ;
// get internal camera parameters
::read_cam_par("campar.dat",&CamParam);
// inverse projection
Row[1] = 100;
Row[0] = 50;
Column[1] = 200;
Column[0] = 100;
::get_line_of_sight(Row,Column,CamParam,&PX,&PY,&PZ,&QX,&QY,&QZ);

Result

::get_line_of_sight returns H_MSG_TRUE if all parameter values are correct. If necessary, an exception handling is raised.

Possible Predecessors

::read_cam_par, ::camera_calibration

Possible Successors

::affine_trans_point_3d

Module

Camera calibration