Hi Rudl, so to start with I'd probably delete many of the curves you've got there since they'll get in the way and also you'll probably want to make sure that the points you have are right on the surface so that you'll be able to get "surface normal snap". Many of the points that you've got there currently are just slightly off of the surface and so you won't get surface normal snap when drawing a line starting on them.

So for this point here for example I just deleted it and placed a new one using "onsrf" object snap so I knew that it was on the surface:

With the point on the surface, you can then draw a line from it and get "surface normal" snap like this:

Here's another view of the same line:

So there I enabled the "Both sides" mode for the line, each one of these lines will be a kind of leveling reference line that you can use to find the 4th planar point starting with just 3.

Once you have drawn in the surface normal line you can then delete or hide the point, because we will be generating a new planarized point that will be pretty close by it and so you don't want to get them confused.

The way to find the 4th point is to start by making a 3 point plane, which you can do either by Draw solid > Plane > 3 points or another way is to draw in 3 lines and select them and run Construct > Planar. Probably hide the big base surface before doing this so it's easier to select and work with the planar fragment.

Now you will have something like this - a triangular plane and a vertical line off to the side a bit:

You now need to extend the plane until it runs into that vertical surface normal line - probably the easiest way to do that is to just grab the corner edit frame handle which I've circled in red above and just drag that off to the side until your plane is big enough to where you see the vertical line being divided by it like this:

Now you can generate the 4th quad point by selecting both that stretched out plane and also the vertical line at the same time and running Construct > Curve > Isect - that will calculate the intersection between the plane and the line and create a point object there. Now you have 4 points that are on one single plane and you can draw lines between them and use Construct > Planar on those lines to build a planar quad face:

So anyway this method might be general enough for you to proceed with creating planar quads across the area that you want, start by placing points directly on the surface, maybe one by one delete each one you've currently got and replace it using "onsrf" object snap in the same general location. Then draw in surface normal lines and delete the on-surface points. Then it's possible to start with one 3sided plane and get an adjusted planarized 4th point by extending the plane and generating the intersection point.

Let me know if this does not do what you need. Basically paneling tools in Rhino would probably automate a bunch of this for you.

- Michael