I try make drag window on canvas (world space) with mouse (screen space) (dont ask me why :), but I have problem with convertion data.delta in OnDrag event for correct window offset in world space.
My formula for perspective projection: delta’ (world space) = delta (screen space) * zFar / zNear. It follows that delta’ > delta, but on real example empirically derived that 1 pixel ~ 0.471 units (zNear = 0.3, zFar = 40, 800x600). I dont undestand why delta of far object less than delta near object?
Rather than trying to manually calculate position, use related Camera functions:
That’s because your code would break on as soon as camera gets an orthographic matrix on it.
There’s also matter of FoV, which you ignore completely.
If you insist on using camera manually, then you should forget about “deltas”, use previous and current world position, and manually multiply those by camera view * camera projection matrix.
To properly multiply a 3 component vector (x, y, z) by projection matrix, you need to convert it into 4 component vector (x, y, z, 1), multiply that by a matrix, then divide x, y and z by w.