I've been working on another new piece for the v2 beta - a new "On surface" object snap for drawing directly on surfaces.

At first I was only going to focus on doing this for planar surfaces, but after messing around a bit it seems to be working pretty well for curved surfaces too, here is a small demo:



You can see there that grid snap is also in effect at the same time for the second pick.

Commands that are planar in nature like Circle, Rectangle, Polygon, will use a plane aligned with the surface normal if you are working in the 3D view. If you pick the second point in the Top, Front, or Right views it will align the object with the world axis of that view instead.

Still some things to fix up for it, but it is generally coming along better than I had originally thought it would.

- Michael

Is it Christmas !!! a lot of presents there Michael.

>>Commands that are planar in nature like Circle, Rectangle, Polygon, will use a plane aligned with the surface normal if you are working in the 3D view.

Just those commands ? can it pick up points on the surface when drawing a freeform curve ?

~Danny~

Hi Danny,

> Just those commands ? can it pick up points on the surface
> when drawing a freeform curve ?

It'll work as a snap in other drawing commands too, just those ones will place points individually on the surface and won't track along the surface normal plane.

For the freeform curve drawing, the result tends to be kind of shrunken down slightly to the inside of the sphere, kind of like if you were to snap a few curve points on to a circle. But if you use more points, it will be only shrunken down a little bit and you can still use a curve like that to trim a hole in a surface with Edit/Trim.

Maybe it would be a good idea if I could detect if all the points of a freeform curve were snapped on to a surface, and automatically project the curve on to the surface in that case instead of having it in the shrunken-down type state, but there can be some tricky things about that... That might have to wait for a while.

There are a few more interesting aspects to surface snapping that I'm going to experiment with in the next couple of days, I may be able to do some stuff for tracking along a surface normal with a straight-snap line (like tangent or perp tracking off of curves), and maybe enable a kind of grid overlaid on planar surfaces...

- Michael

Hi Michael,

> For the freeform curve drawing, the result tends to be kind of shrunken down slightly to the inside of the sphere,
> kind of like if you were to snap a few curve points on to a circle.
> But if you use more points, it will be only shrunken down a little bit and you can still use a curve like that to trim a hole in a surface with Edit/Trim.

That's fine, we could project those curves manually using curve -> project, after that if you move the original points ( if they stay associated to the surface) would the resultant projected curve update ?

~Danny~

Hi Michael,

>>It'll work as a snap in other drawing commands too,

Sounds like a nightmare.
How will you know if you are snapping on a line in front of a surface, on a surface, or a line/surface behind a surface.
I have to waste too much time now constantly zooming in/out having to verify snaps made.

- manz

Hi Danny,

> That's fine, we could project those curves manually using
> curve -> project,

Actually, you don't have to do that, this kind of projection is also already built directly into Trim.


> after that if you move the original points ( if they stay associated
> to the surface) would the resultant projected curve update ?

It will if the result of the projection is just one curve, like if you use Mode: Closest pt for the projection. But this will be pretty awkward, you will have to keep both the old curve and the new curve around.

History needs to be tuned up some more for that to work very smoothly.

- Michael

Hi Steve,

> Sounds like a nightmare.
> How will you know if you are snapping on a line in front of
> a surface, on a surface, or a line/surface behind a surface.

It's really easy to tell - it puts up a label on the point that actually says "On srf", so if you see "On srf", you've got that snap. If you don't see "On srf", then you don't have it - it's really pretty straightforward.

It also works similar to the "on" snap for curves, it has the lowest priority (even lower than curve "on") and only kicks in if no other snaps were targeted.

Basically it will only kick in when in v1 you were going to miss all snaps and your point was going down to the construction plane instead.

If it does get in the way, there is an easy method to turn it off, there is a new "On surface" checkbox in the list of object snaps on the menu that pops up when you move over the Object Snap button on the bottom toolbar. You can uncheck that to disable if it causes you any problems.

It's brand new but so far it seems to be working a lot more smoothly and easily than I had expected, so nope, not looking like any kind of nightmare so far at least.

- Michael

Hi Michael,

>>It's really easy to tell - it puts up a label on the point that actually says "On srf",

But which surface? front/back/distant. As with current snaps for "On" the side/edge of a cube in a 2d view, sometimes the snap will be on the front line/edge, sometimes on the back.

>>Basically it will only kick in when in v1 you were going to miss all snaps and your point was going down to the construction plane instead.

As with snap "on" a curve, that over-rides the grid snap, will the surface snap do the same?

>>If it does get in the way, there is an easy method to turn it off,

You have mentioned before that you dont want users to have to do that.


- manz

Is it possible then to use this 'on surface snaping' to drag and align objects over a surface nornal ?

Hi Steve,

> But which surface? front/back/distant. As with current snaps for
> "On" the side/edge of a cube in a 2d view, sometimes the snap
> will be on the front line/edge, sometimes on the back.

It will be the surface that is being displayed at that point, so the one most to the front.

Again this is very straightforward - it snaps to the object that you can see that is under your mouse, there isn't much mystery about it.

You won't really be able to grab a surface that is being displayed edge-on with this snap, surfaces like that are generally not visible (their edge curves are because edges are drawn with a thickness).


When you run into that problem with "on", the solution is generally to switch to the 3D view so you can more easily target one particular edge with your mouse. This surface snap will be similar - if the surface you want to snap on to is edge-on to your current view, you will need to switch to some other view where you can clearly see it in order to snap on to it.


> As with snap "on" a curve, that over-rides the grid snap, will the
> surface snap do the same?

For curved surfaces yes - for planar surfaces I'm going to see if I can make grid snap work with them, but I'm not quite sure how that will work yet, the grid may be relative to a base point in the object rather than the world grid...

Another thing I was thinking of was possibly only enabling the onsurface snap in the 3D view and not in the ortho views at all. Then that would not interfere with grid snap there.

Maybe I can tweak things a bit to make grid snap co-exist better with both the regular "on" snap as well as the new one though, I have an idea on that.


> You have mentioned before that you dont want users to have to do that.

Not for general simple use. But if you have some particular workflow that it ends up causing a problem for, turning it on or off will certainly be a solution for that.

- Michael

Hi PaQ,

> Is it possible then to use this 'on surface snaping' to drag
> and align objects over a surface nornal ?

Not really by itself yet - it is basically something that assists commands that pick points.

I do want to make a set of orientation commands which would be focused on doing that (moving an existing object to align with a surface normal), and certainly this snap will be a part of how some of those commands will work.

However, this new snap should allow for drawing brand new objects aligned to a surface normal right from the beginning, once I get the normal-line straight snap working.

- Michael

Hi Michael,

>>It will be the surface that is being displayed at that point, so the one most to the front.
>>Again this is very straightforward - it snaps to the object that you can see that is under your mouse, there isn't much mystery about it.

But that is how I would expect it to work now for snapping onto the edge of a cube in 2d view,.. but it does not, the snap changes from front to back (or top to bottom depending on 2d view) as you move around the edge.

>>When you run into that problem with "on", the solution is generally to switch to the 3D view so you can more easily target one particular edge with your mouse

I think it strange to have to go to 3d view to be able to correctly create a planer(2d) curve via snapping.


- manz

Hi Micheal,
Referring to your animated gif, if we were to draw a rectangle normal to a contoured surface and apply a planar surface to the rectangle, could we then use that planar surface as a sort of datum plane to draw on with this new "On Surface" command ?

~Danny~

Sounds great!

Marc

Hi Danny,

> could we then use that planar surface as a sort of datum plane to
> draw on with this new "On Surface" command ?

Yup, that will definitely work - it will be kind of a basic way to set up a drawing plane.

You actually don't have to create a rectangle first and then make a plane second, you can create the plane all in one step by using Draw solid / Plane.

- Michael

Hi Michael,
The 'What's new' in V2 sounds exciting, can't wait! and thank you Michael for being so dedicated to your software, your tech support runs rings around the big guns in the design world.

Cheers
~Danny~

Hi Steve, today I did some experimentation with making "on" snap and grid snap co-exist better.

One thing I tried was letting grid snap override on snap if your mouse was close to the grid intersection point.

That didn't really work out very well, it did let grid snap work but at a pretty normal zoom level there is always a grid point close to your mouse so it basically has the effect of disabling "on" snap entirely.

What I think I'm going to do is for "on" snap I will only let grid snap override "on" snap if the object snapped on to is a line that is actually running along a grid line.

For "on surface" snap - I will disable "on surface" snap in the ortho views if grid snap is also turned on, and maybe have an option for having it disabled in all views if grid snap is on.

I think those tune-ups will help make things work more smoothly when all kinds of snapping are simultaneously enabled.

I've also made a related tune-up to straight snap - both "on" snap and "on surface" snap will now have a lower priority than straight snap.

- Michael

Hi Michael,

Could you possibly make it so that the "on" snap is only current for selected objects?


- manz

Hi Steve,

> Could you possibly make it so that the "on" snap is only
> current for selected objects?

It should be easy for me to put in an option for that.

- Michael

Hi Steve, I think I've got the combination of on/onsrf with grid snap worked out now.

If you have grid snap enabled, doing an "on" snap on to a line that is aligned with the grid's x, y, or z axes will also get grid snap applied to it.

Similarly, if you do an "onsrf" snap on to a plane that is normal to one of those axes, grid snap will also be applied there. So for instance if you draw an axis-aligned box, you can grid snap on to points on the box's surfaces.

There are some additional settings (for now just in the moi.ini file) that will allow some control over some additional details:

[Drawing Aids]
DisableOnSrfInOrthoWhenGridSnap=y
DisableOnSrfWhenGridSnap=n
OnSnapOnlyToSelected=n


The first setting (turned on by default), disables onsrf snap in ortho views when grid snap is enabled, except still allowing it on axis-aligned planes which snap to the same grid at that plane's elevation. This should generally allow regular grid snapping kind of behavior in ortho views, but still allow you to place an "onsrf" point on to a surface in the 3D view.

The second setting (off by default) will cause onsrf to be disabled entirely when grid snap is active.


Also the last setting doesn't have to do with grid snap, but instead only enables "on" or "onsrf" snaps on to selected objects only (and construction lines) instead of all objects. That may help you gain some additional control over that snap.


Also "on" and "onsrf" will not kick in if a straight-snap line is active, which is different than v1 for "on".


There are a still a couple of snapping areas that I am going to look in to like avoiding hidden-point snaps if hidden lines are turned off, but I think that the combination of grid snap + on snaps is worked out now.

- Michael