Thanks again Steve.
It looks like I’m not far from the goal but I miss a kind of scale factor.
I get the Xform:
ON::world_cs, ON::camera_cs, world2camera);
then activate page view’s main viewport
then compute projectedPoint:
ON_3dPoint projectedPoint = world2camera * myWorldPoint;
then add a text block by running _Text command:
myStream << L"-_Text " << projectedPoint.x
<< L"," << projectedPoint.y
<< L"," << projectedPoint.z
<< L" Height=5 " << "myText";
I’ve run a test with a selection of several objects. And the resulting text blocks almost well positioned: there is just a scale factor (see attached snapshot).
Any clue about which scale I should use ?