converting screen coordinates to world coordinates

rogerdv · Post by **rogerdv** » Sat Dec 13, 2003 4:14 pm

I need to convert screen coordinates (x,y) to the corresponding coordinate in the 3d world. I cant find in the docs any idea about how to do it. Can somebody point me in the right direction?

Boogle · Post by **Boogle** » Sat Dec 13, 2003 5:49 pm

In the collision manager, you have getRayFromScreenCoordinates which will get you the ray from the camera's position all the way to the end of the field of view. The ray represents the possible positions in 3d space the 2d position could represent. You can then determine how far along the ray you want to go. The collision manager has some other functions for converting 3d to 2d or vice versa, such as selecting the scene node located at a screen position.

The documentation for getRayFromScreenCoordinates is at http://irrlicht.sourceforge.net/docu/cl ... er.html#a3

rogerdv · Post by **rogerdv** » Sat Dec 13, 2003 6:57 pm

I cant pick a node, because the "floor" is only one node: a bsp mesh. I need to get an aproximate 3d coordinate that corresponds to the screen 2d coordinate of the mouse click.

Boogle · Post by **Boogle** » Sat Dec 13, 2003 7:04 pm

You will have to use getRayFromScreenCoordinates then and decide on a point along the ray. There is no single 3d point that corresponds to a 2d screen coordinate.

rogerdv · Post by **rogerdv** » Sat Dec 13, 2003 8:20 pm

Thanks. Really, there is no a single point. And as i only need x and z (y is supposed to constant), the only thing I need to know is how to extract x and z from the ray, given a constant value of y.

Boogle · Post by **Boogle** » Sat Dec 13, 2003 8:47 pm

Ah, ok. Well then, after you get your ray, the ray has a property called start, which will be an x,y,z point just in front of the camera, with an offset related to the screen position. If you want a point that is x distance away from the camera at the given mouse position, you can use something like:

vector3df lineVector = ray.getVector().normalize();
vector3df pos = ray.start + lineVector*x;

stampsm · Post by **stampsm** » Mon Dec 15, 2003 4:10 am

is there some way to obtain the z buffer value from the engine if you do this then all you have to do is follow the line you get for the value obtained from the z buffer to get the exact x,y,z value of any pixel on the screen
i haven't tried this but if you can get the z buffer value it should be quite easy