what's the Geometry traversal's application in houdini?

[amin.khormaei]

what's the Geometry traversal's application in Houdini?

best regards.

Edited June 17, 2021 by amin.khormaei

[acey195]

Hey, you mean this? :

https://www.sidefx.com/docs/houdini/vex/geometry.html

it allows you to run your vex code over for example primitives, while retrieving(or changing) data on points or vertices among other things

Edited June 19, 2021 by acey195

[amin.khormaei]

Could you show me a simple example?

[acey195]

why not

you could do something like (creating a prim attribute from points data):

//run this over primitives, to calculate the perimeter using the point data.
//note that this is not the most efficient way to do this, but as an example to what options this gives you:

int pts[] = primpoints(0, @primnum);
float sumOfTheDistances = 0; 

for(int i=0; i < (@numvtx-1); i++){
	vector pos0 = point(0, "P", pts[i]);
	vector pos1 = point(0, "P", pts[i+1]);
	sumOfTheDistances += distance(pos0, pos1);
}
                             
f@perimeter = sumOfTheDistances; // create a primitive attribute

or the other way (creating a vertex attribute while processing prims):

//run this over primitives to calculate the same thing a polyframe would, but as a vertex attribute, so you do not have to make the points unique:

int verts[] = primvertices(0, @primnum);
vector forwardDir;

for(i = 0; i < (@numvtx-1); i++){
	vector pos0 = point(0, "P", vertexpoint(0, verts[i])); //get the point data, from the vertex (just to demo the conversion, 
	vector pos1 = point(0, "P", vertexpoint(0, verts[i])); //the "P" data should also be fetchable here using vertex() instead of point()
	forwardDir = normalize(pos1 - pos0);
	setvertexattrib(0, "N", verts[i], -1, forwardDir);
}

setvertexattrib(0, "N", verts[-1], -1, forwardDir); //put the same data on the last vertex, as the second to last one

note that I have coded this "blind" (did not test it) so hopefully the code runs, but there could be a typo somewhere

[amin.khormaei]

Thank you , you made my day

[konstantin magnus]

My favorite "traversal" adds primitive objects to points.
Unfortunately there is very little types to choose from.

// Choose random primitive types from list
string types[] = {'sphere', 'circle', 'tube'};
int index = int(rand(i@ptnum) * len(types));
int prim_add = addprim(0, types[index], i@ptnum);

// apply point orientation from polyframe node
matrix3 xform = set(v@tangentv, v@N, v@tangentu);
scale(xform, 0.05);
setprimintrinsic(geoself(), "transform", prim_add, xform);

 

add_prims.hipnc