can't snap to point on other sketch

[titanium.rainbow]

hi, sorry if this is annoying.  i read a few other posts on this topic, but i don't understand the answers.  i have all the necessary settings turned on in Preferences/Design, but it's still not working.  i'm trying to follow this tutorial:

https://www.youtube.com/watch?v=HmgwKewMcw8

around 37 minutes in, he's drawing arcs on surface planes.  he is snapping the start of each new arc to the end of the previous arc, on an inactive sketch plane.  i cannot do this, whether or not i have Snap checked in the Sketch Palette.  i get an X-shaped snap when i cross the edge of the surface, but i do not get the box-shaped snap when i cross the point that terminates the arc i'm trying to select.  i also don't understand how to use Look At, which other have suggested; it seems to fly to random vantage points.

POSSIBLE SECOND QUESTION:

as a result of being unable to snap, the arcs together, i am unable to later create a Patch from those top edges after trimming the surface segments above the arcs.  i also tried the Move command, using the point-to-point option for trying to bring the endpoints together.  while it correctly identified the points and snapped them together, it seems that was insufficient to create a continuous edge.  the Patch preview showed the correct surface, but i got a Compute Failed error when i said OK.  i am posing this as a second question, because it crossed my mind that i might have to use imported geometry from someone else's file someday, and i'd like to know how to fix a problem like this rather than having to rebuild the sketch lines as i must do now.

sorry, just another frustrated n00b...

[jhackney1972]

He is indeed creating a sketch on that first surface plane at time index 35:55.  The "multiple arcs" as you call them are not arcs but one continuous Fit Point Spline.  A Fit Point Spline is controlled by points which he is selecting.  It seems like arcs but he is just picking points that make the spline follow arc patterns.  He is "snapping" to a coincident point on each side of the surface.  I created a short Screencast where I demo the creation of a surface, started a new sketch on it, drew a Fit Point Spline and showed you how the automatic sketch constraints work on the edges of the surface.  I also show you the advantage of the Look At command.  Make sure you have the Show Constraints on in your sketch panel, it will help you see the sketch constraints after they are applied.  I have attached two screen captures, one of the Sketch Panel marking the Show Constraints and one where I am hovering, while still in the sketch, over one endpoint of the spline to cause the Coincident Sketch constrain symbol to appear.

I think your the second part of your question will become clear once you understand the first part.  I would suggest that you repeat over and over the videos you watch at the point where you are having issues and you will probably see what you have missed, in this case the sketch and at point 35:59 where he selected the Fit Point Spline command.  The icon is very similar to the line command, that is why it is easy to miss.

Learning, on your own, can be challenging so please do not hesitate to come back if you get hung.  One thing you can do to help us help you is to attach your model to your post so we can help you directly on your work.

[titanium.rainbow]

hi John,

thank you for your prompt reply and video!  i must apologize, because i was expecting to get an email notification, as i normally do, when a get a response to a query.  however, it seems i did not, and today i thought i should log in and see if there was a letter in my mailbox.  otherwise i would have responded much sooner.

i understand everything you showed in the video; i guess i was using Look At with too many things selected at once.  but what i still don't understand is what Jason was doing in his tutorial:

1. after you draw your spline across the surface, you must then jump over to the next [perpendicular] surface and draw a spline attached to the endpoint of the previous one.  how is this possible?  once i am on sketch #2, i cannot reference objects on sketch #1 in this way.  i also tried using Move [point-to-point] after drawing splines 2, 3, and 4; it looked like it was creating the proper attachments, but after i had finished Trimming the tops and Stitched the box together, Patch still wouldn't recognize the spline borders as a continuous edge.  i even tried doing the entire box as one 3D sketch, but i found that i was unable to get the cursor to understand where i was trying to place the unattached endpoint, and the splines seemed to "float" near the surfaces, but not attach to them.

2. furthermore, it crossed my mind that i might someday have to import a client's file with bad geometry like this, and fix it myself.  if the Move command won't fix it, i don't know what will.  it seems like such a simple thing, i don't get it.

i await your reply, should you choose to accept this dangerous mission...

[g-andresen]

Hi,

I think an essential element to your concern is the projection of lines, points, edges... to be used for active sketches. This can be done automatically if you have allowed this in the preferences

or manually (better) via the Sketch Tools > Project or alternatively with the shortcut "P".

günther

[titanium.rainbow · Accepted solution]

hi Gunther, thanks for your assistance.  i already have the auto-project settings on in Preferences/Design, and in Sketch Palette.  but it still doesn't allow me to lock on the endpoint of a spline on an inactive plane.

i just managed to do it by manually projecting each endpoint, and then i could lock the next spline to it, but it's sort of glitchy.  it took me a few tries to get it right.  i was able to trim all 4 surfaces to the spline edges, and then Patch the top of the box, but the Patch tool couldn't recognize a continuous edge on top.  it did let me select the bottom of the box as an edge, but i had to select all 4 top edges separately.  when Jason did it, it looked easy, but it's not working for me.

weird...

[laughingcreek · Accepted solution]

do yo have 3d sketching enabled in your preferences?

and in your sketch palette?

[titanium.rainbow · Accepted solution]

no, i don't.  i tried it both ways.  can't make it work either way.

[laughingcreek · Accepted solution]

well, we're all just shooting in the dark.  can you post a screen cast and show what your doing.  this is working for me.

[titanium.rainbow · Accepted solution]

hi again, sorry for the overly brief reply, and thanks for responding.

i should have said that i first tried doing the splines in 2D, but could not snap the new spline to the previous endpoint.  then i tried 3D, which allowed the snap, but the new spline seemed to hover about 1mm off of the new surface, i don't know why.  then i went back to 2D and tried again, after which i started asking for help.

checking the auto-project options doesn't seem to do anything.  when i used the Project command on the old spline, i still had a hard time snapping to the endpoint.  but for some reason, when i only Project-ed the endpoint of the spline, i was able to grab it.  i still don't know what Jason was doing in the video, but he didn't seem to be using Project at all.

i don't think sending a screenshot or sharing the file will accomplish anything at this point.  i made it work, but i don't know why it was such a hassle.  i can live with it the way it is.

i guess i should close out this thread now?