i know how to converting 2D mouse coordinates to world coordinates,but whether the world coordinates convert into a 2D mouse coordinates if i know the world position ,uv,and the normal of the face.
Maybe this helps? https://manu.ninja/webgl-three-js-annotations/ If this link dies, it’s about using
vector.project(camera); to convert a 3D world position to screen coordinates.
vector.project( camera );
This only converts a vector to normalized device space. You still have to map the vector to 2D screen space. Something like:
vector.x = ( vector.x + 1) * width / 2; vector.y = - ( vector.y - 1) * height / 2; vector.z = 0;
height represent the dimensions of the canvas (
@Mugen87 thanks very much for this. Why do you add 1 to the x coordinate and subtract one from the y coordinate?
After the call of
Vecto3.project(), the components of
vector are in the range of [ - 1, + 1 ] (assuming the vector originally was inside the view frustum). The mentioned calculation will then convert this range to [ 0, 1 ] and then multiply the values with the respective dimensions (width or height). The y-coordinate is handled in a special way because in screen space the origin of the coordinate system is top left (and not bottom left).
Awesome explanation, thank you very much!