i'm in the process of making a gis with directx and i have to drag the mouse around the map see different part of it (like google map). The main problem with this is the speed of the drag when zooming in and out. Setting the scroll speed to a static number when zoom out and draging the map is easy but when I zoom in i have to slow the speed of the dragging in order to give the gis a proper smooth movement. I wonder if anyone has any experience with this and if someone has any idea of a mathematical formula to do this smoothly. The way I do this right now is the following and static but is working well. thanks in advance.
If you're using an orthographic projection, the area the camera can see has a width height, and depth. Transform the mouse position data to normalized coordinates (a range from zero to one) if you're currently using pixels or something else. Then multiply the size of the camera view with delta mouse position, negate, and use the result to translate the camera.
If you're using a perspective projection this won't work, so let me know if that's the case.