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_Alex_

Direct3D IM object picking

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Hi,

here''s a short algorithm for picking objects

1. Compute a ray with the origin in the camera position
2. Pick the object that this ray intersect closest to the camera

The keywords here are ''ray'' and ''intersect''.

The ray''s direction is computed by unprojecting a screen coordinate by multiplying it with (ViewMatrix*ProjectionMatrix*ViewportMatrix)-1 and then subtracting the camera''s position from the result.

Then you check for all objects if the ray intersect any of their triangles. Then finally you pick the objects which was intersected the closest to the camera.

You can find info on how to check if a ray intersects a triangle here: Fast ray/triangle intersection test



- WitchLord

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