in houdini,
how to draw a nurbs curve directly on a nurbs surface without using project/ray SOP? is it possible?

thx

Hit Ctrl+j to turn on snapping.
Hit Ctrl+Shift+J to open the snapping options. Once there turn on Primitive Snapping.

It never occured to me that the primitive snap option did that, that's awesome! I owe you a Red Bull.

thanx,
the only problem that it only snap the points , means if i draw the nurbs curve on a sphere, then the points of the curve is on the sphere's surface , but the curve itself cannot really stick on the surface.
or did i miss something?

metaclay
thanx,
the only problem that it only snap the points , means if i draw the nurbs curve on a sphere, then the points of the curve is on the sphere's surface , but the curve itself cannot really stick on the surface.
or did i miss something?

Yes it will only snap the points, if you need to curve to fit exactly on the surface then you'll need to use more samples (points) to create the curve.

metaclay
thanx,
the only problem that it only snap the points , means if i draw the nurbs curve on a sphere, then the points of the curve is on the sphere's surface , but the curve itself cannot really stick on the surface.
or did i miss something?

that's because of the nature of the primitives and the curve you're drawing…

in short.. nurbs curves are based on point which doenst live on the curve itself.. so you might want to draw a polygon curve which instead have points on the curve…. over the nurbs surface.

hope this helps.

If you change the method from CVs to Breakpoints that will get you much closer.

Alternative approach would be to use a project sop to build the curve into the surface then use a profile sop to extract it back out.