I have 2 lines in 3d coordinate system AB and AC. I need to find a point "D" that lies on the line AB such that the angle between DA and DC is 90 degrees.
Next might be irrelevant information but: A is position of a perspective camera. B is the position where the camera is looking. C is the position of an edge.
I'm making a 3d modeling a tool and I have to grab an edge and drag it in 3d space. To change the depth I'm going to use the mouse wheel which is nothing you just have to bring it closer or further to the camera. But I'm not understanding how to the horizontal and vertical movements according to the camera.
What is bothering me is that if the 3d point C according to the 2d view plane of the camera is (20,89) if I drag the mouse from (20,89) to say (30,50) what would the new 3d position be. My idea is to consider a flat screen in 3d on which C lies and the screen is parallel to the camera.