Projection of Sketch
How to project sketch or snap points of sketch from one plane to another plane in CATIA?
In the sketch tracer there is a button called Project 3D elements. This allows you to project any sketch lines/points from one sketch to another. The pictures below show an example of how to use it.
1-Sketch to be projected. Plane 1 is where sketch 1 is, and plane 2 is where I will make the 2nd sketch.
2- In the second sketch I press the Project 3D elements button and project the circle in the 1st sketch onto the 2nd sketch. Projected elements are yellow.
3- You can use them as you use any normal lines in sketch with the usual relations.
4-How it looks when finished.
4- If you change the circle in the 1st sketch, it will change in the 2nd.
As usual when learning any CAD, I recommend that you play around with this feature to find out how powerful it is. You can use this tool for projecting 3D solids and surfaces onto sketches too. You have to be careful however with what you link to your sketch, since if you delete Sketch 1, sketch 2 will not be able update your circle. If you want to project the geometry and then delete the relationship, right click on the yellow circle, press Mark1.object, and finally click Isolate. You keep the projection but if you change Sketch 1 it will not change Sketch 2.
Hope this was useful, if you have any more questions about this element, I'll answer (if I can of course :) ).