Cinema 4D Release 17 includes several methods for matching vector paths to 3D geometry. The Project Spline from prior releases can be used to match a spline to geomety based on an axis of view. With the new Spline Smooth tool you can interactively project a spline onto geometry, or utilize new spline snapping with either the Pen or Sketch tool to draw splines directly on geometry.
One of the coolest aspects of the new spline tools in Cinema 4D Release 17 are some new options to project your splines onto geometry in your scene. Because really, if we're just dealing with splines in two dimensions, it's not a 3D application, right? So you're probably familiar with the old option to project splines directly onto geometry. So if I have a spline selected with points, and I right-click and choose Project, I can choose the plane that I want to project onto, like down the XYZ plane. And hit Apply, and it's going to project those points down onto the landscape. So now I have a spline that sort of matches the landscape. One of the downsides to this command is that its resolution is only as good as the subdivision of your spline. So you might have to tweak the resolution of your spline back and forth until you get a nice projection that really matches the geometry. Well, in Cinema 4D Release 17 we had the option to now project interactively, regardless of the spline resolution. So I'm gonna undo that projection that I did a second ago. And now what we're gonna do is go ahead and expose the top view, and I'm going to enable the Spline Smooth tool. Now, by default, what you're going to see is the smooth parameter is enabled here at 50%. And that's nice, because it can kinda smooth out the stroke of a spline. But what I'm gonna do is uncheck that, and instead choose the Project option. And now, if I simply drag over this spline, and you look in the left-hand side, you'll see that it's projecting over the geometry as I drag. And I'll just enable the sweep once more so you can see really clearly that I've now got a spline that precisely matches the landscape that's underneath it. Being able to interactively project our splines is already super cool, especially if you have an existing spline, like a logo, that you need to project onto geometry. What if you're trying to draw a new spline? Well, one of the really nice enhancements to the spline tools in Release 17 is that they now support snapping. So if we go in here and enable Snap, and just go in and make sure that Polygon Snap is on as well, we can use either the Pen tool or the Sketch tool to draw a new spline that snaps to the existing geometry. So I'm just gonna choose the Sketch tool, which you'll recall is the new tool that allows you to very quickly freehand draw a spline out, but in a very smooth way. And we can just simply drag right here in the view, and you can see that what it did is automatically add a segment onto my existing spline. If you wanna create a new spline, you can always check this check box here in the attribute manager. But this is actually kinda nice, because I can just draw additional paths down the mountain. Now, of course, with the spline Sketch tool, I can continue to refine these splines by increasing the radius within the tool. And now as I draw new splines, any spline that's within the radius is going to be refined, rather than a new spline being created. And you can add some blending, too, to blend between the spline that's already there and the spline that you're drawing. Now, as I mentioned, you can also do this same snapping with the Pen tool. I usually prefer using the Sketch tool, because it automatically creates the resolution necessary to properly project the spline onto the geometry, so you have all the points that you need. With the Pen tool, you'll have to interactively create the points necessary, and so you might not get as exact a match of the spline onto the geometry. So those are a few options for how you can project splines in Cinema 4D Release 17.