How can I edit this polysurface?

Hi, I am new in Rhino and trying to model my first house.
I followed some tutorials to make the terrain but I’m having some trouble with some geometry like the stair here. I edited the surface with solid points, but now that I’ve extruded it I cannot turn them on.
How can I keep on editing now? For example, I would need to extrude a bit more the area around the beginning of the stair to then carve out a flat platform
Also how can I make a smoother transition between the terrain and the already carved out base of the house? There is one area that is a garage, so I don’t want there to be a “step” between the terrain and the floor

I read I should explode the polysurface and then work with the surface, but when I do that and turn SolidPtOn it looks like in the second image, I only see points around the geometry I carved

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Bit tricky…
Just some basics you might know or not know:
For a single surface, trimmed or not, you can turn on Control Points (command PointsOn) as well as Solid Points (SolidPtOn).
When multiple surfaces are joined together to form a polysurface, only SolidPtOn will work.

So, to have more granular control over that top surface, it’s probably best to either explode the whole polysurface, or extract only the top one, using ExtractSrf. Then deform it as needed, then join it all back together.

Are you using the Gumball? You could put it to good use here. I’d recommend to set it to ‘snappy dragging’ in it’s menu ball up front, because then it will snap to things when you move or relocate it (holding CTRL).
image

To make the terrain match nicely with the garage floor,
image
you can then select this,
image
relocate the Gumball to the garage floor, click on the vertical axis,
image
and enter 0 to scale those points to align.
image

There are many other ways, of course, like Align _Top.

To get a flat surface at the stair bottom, either scale the surrounding control points to 0 vertically (given there are enough of them - use Rebuild to get a finer grid of points for the surface), or use BooleanDifference to cut off the ‘hilltop’ with a box.

Happy modelling!

Hi! Thank you so much for the detailed answer. My main problem now is that I can’t turn on the control points on the top surface. As you can see in the image, I just get the ones around the area I substracted to place the house.

The explanation about the garage floor was very helpful.
Anyways, I’ll keep on trying. I’m still used to SketchUp so I get quite frustrated with this problems where it seems that I can’t go back and forth editing the terrain as needed as if it was a mass.

Strange. You should definitely be able to turn on control points for that surface, not just solid points.
What is written in the command line when you select it?

image

Here it says “1 open surface added to selection”. Then it should work.

Yes, it says exactly that…
I’m attaching a file with just the terrain.
Terrain.3dm (395.0 KB)

Works here…
image

PointsOn

Ok apparently I was trying SolidPtOn only. Thank you so much