Two drawing question

[victor-freedom]

1、How to convert a 3D coordinate system into a corresponding 2D coordinate system based on camera's eye and target parameters？
I want to draw an arrow pointing to a certain point，And rotate along with the rotation
2、How to draw text on the canvas?

I just want to achieve the effect shown in the above image

[aothms]

You're in luck we have sth related to this https://github.com/opensourceBIM/BIMsurfer/blob/master/viewer/svgoverlay.js

It's used for measurements for example, draw a polyline as 3d points in the model, but render them as 2d SVG elements with lengths, because text looks so much better in svg than webgl.

hope that helps.