Perspective Projection: determine the 2D screen coordinates (x,y) of points in 3D space (x,y,z)
I wish to determine the 2D screen coordinates (x,y) of points in 3D space (x,y,z).
The points I wish to project are real-world points represented by GPS coordinates and elevation above sea level.
For example: Point (Lat:49.291882, Long:-123.131676, Height: 14m)
The camera position and height can also be determined as a x,y,z point. I also have the heading of the camera (compass degrees), its degree of tilt (above/below horizon) and the roll (around the z axis).
I have no experience of 3D programming, therefore, I have read around the subject of perspective projection and learnt that it requires knowledge of matrices, transformations etc - all of which completely confuse me at present.
I have been told that OpenGL may be of use to construct a 3D model of the real-world points, set up the camera orientation and retrieve the 2D coordinates of the 3D points.
However, I am not sure if using OpenGL is the best solution to this problem and even if it is I have no idea how to create models, set up cameras etc
Could someone suggest the best method to solve my problem? If OpenGL is a feasible solution i'd have to use OpenGL ES if that makes any difference. Oh and whatever solution I choose it must execute quickly.
Answer
Here's a very general answer. Say the camera's at (Xc, Yc, Zc) and the point you want to project is P = (X, Y, Z). The distance from the camera to the 2D plane onto which you are projecting is F (so the equation of the plane is Z-Zc=F). The 2D coordinates of P projected onto the plane are (X', Y').
Then, very simply:
X' = ((X - Xc) * (F/Z)) + Xc
Y' = ((Y - Yc) * (F/Z)) + Yc
If your camera is the origin, then this simplifies to:
X' = X * (F/Z)
Y' = Y * (F/Z)