Python How To: Get Point Position, Store It In A String

[pclaes]

Hi guys,

I came across a little problem and I am trying to get through it with python. I have experience with scripting but not with python in houdini.

I have to convert a polygon curve to a nurbs curve, but... the polygon points need to be used as breakpoints (curve points), not as Cv's. The only way I see of doing it is of attaching a "curve sop" to the polygon curve. But the curve sop takes a string as input which is like: "x1,y1,z1 x2,y2,z2 x3,y3,z3 x4,y4,z4 ...." so basically it takes in the translation values of each point. I need to generate that string. I am currently looking into python as it seems like a simple for-loop and in mel I would write it a bit like:

string result = "";

for( i=0, i < $NPT, i++)

{

result += getTranslateX + "," ;

result += getTranslateY + "," ;

result += getTranslateZ + "," ;

result += " ";

}

return result;

So far I got an new python sop that does:

geo = hou.pwd().geometry()

pos_string = geo.addAttrib(hou.attribType.Point, "posString", "")

for point in geo.points():
	print point.position()

Now I think it would be best to store the resulting string on the "detail" level rather then on point, but I haven't figured that out yet.

Also I find navigating the help files not that easy (as in Maya), but that is probably because I am not used to it yet.

thanks for any help!

Peter

[graham]

To get the positions into a string you just need to do:

result = ""
for point in geo.points():
	result += str(point.position()[0]) + ','
	result += str(point.position()[1]) + ','
	result += str(point.position()[2]) + ' '

geo.addAttrib(hou.attribType.Global, "posString", "")
geo.setGlobalAttribValue("posString", result)

Detail attributes are referred to as Global attributes in HOM.

Edited February 22, 2008 by graham

[petz]

you can also use point numbers as input for the curve sop like p0 p1 p2 ....

just put down a partition sop and use p$PT as rule, so you

poly_to_nurbs.hipnc

[pclaes]

Thanks guys !!

I'll try it out asap.

[sibarrick]

Try the fit sop

[rdg]

to complete the list:

you could also group all or a subset of the points with a groupSOP and use this expression to generate the string:

`

[pclaes]

thanks again !

I have tried out all solutions and they are all very interesting!

I love some of the creative expression use!

Never though of using the partition sop as a way of generating a string and not actually using the groups, just their names. The fit operator works too, but gives slightly different results.

rdg: that is some very cool name linking, it took me a bit to figure out your expression but using opinput(".", 0) to refer to the previous node and combining it with $OS to get to that group is a very nice way!

I've put all these different solutions in one file for my own personal future reference. I thought I attach it so other people can learn from this if they come across similar challenge.

python_curve_string_01.hip

[JoshJ]

Hi Peter,

I tried loading up your file and I'm getting this error message for the curve_test1 sop:

# Couldn't find Python code. Please check that

# oplib:/Sop/curve_test?Sop/curve_test.py is in the proper location.

thanks again !

I have tried out all solutions and they are all very interesting!

I love some of the creative expression use!

Never though of using the partition sop as a way of generating a string and not actually using the groups, just their names. The fit operator works too, but gives slightly different results.

rdg: that is some very cool name linking, it took me a bit to figure out your expression but using opinput(".", 0) to refer to the previous node and combining it with $OS to get to that group is a very nice way!

I've put all these different solutions in one file for my own personal future reference. I thought I attach it so other people can learn from this if they come across similar challenge.