VEX compare attrib values to each other

[Iraklo]

Hi guys,

 

how do I compare to each other and get max and min values of attribute for different elements.

 

Basically I want to compare these guys and get min and max.

[konstantin magnus]

Use an attribpromote from points, verts or prims to detail and set the promotion method to min or max.

[konstantin magnus]

As you requested a VEX solution, I would put something like this into a detail wrangle:

int all = nvertices(0);
@min = vertex(0, "uv", 0);
@max = vertex(0, "uv", 0);

for(int i = 0; i < all; i++){
    float compare = vertex(0, "uv", i);
    if(compare < @min) @min = compare;
    if(compare > @max) @max = compare;
}

Unfortunately I would not know how to access a single vector component in this manner:

@min = vertex(0, "uv.y", 0); // these lines
@max = vertex(0, "uv", 0).y; // do not work

Maybe someone can help me out here?

[f1480187]

@konstantin magnus, try function-style cast:

vector(vertex(0, "uv", 0))

 

[konstantin magnus]

@f1480187, ah thank you! So I guess, its:

int all = nvertices(0);
@min = vector(vertex(0, "uv", 0)).y;
@max = vector(vertex(0, "uv", 0)).y;

for(int i = 0; i < all; i++){
    float compare = vector(vertex(0, "uv", i)).y;
    if(compare < @min) @min = compare;
    if(compare > @max) @max = compare;
}

 

[Iraklo]

@konstantin magnus

@f1480187

Thanks for help guys

[ikoon]

I am used to access vector component like this, I hope it is a good solution as well:

    vector compare = vertex(0, "uv", i);
    if(compare[2] < @min) @min = compare[2];

Edited August 21, 2017 by ikoon
grammar check

[petz]

you could put the following two lines in a vertex wrangle:

setdetailattrib(geoself(), "min_val", @uv.y, "min");
setdetailattrib(geoself(), "max_val", @uv.y, "max");

 

[Iraklo]

@ikoon @petz

Thanks for reply guys.

One quick question here: how is it possible to create array from numbers I marked in the first post's screen? Right now it's irrelevant, but in future it would help me.

[f1480187]

You can do it in Detail Wrangle:

for (int i = 0; i < @numvtx; i++)
{
    vector uv = vertex(0, "uv", i);
    append(f[]@uvx, uv.x);
}

Or in Vertex Wrangle (very slow):

float uvx[] = array(@uv.x);
setdetailattrib(0, "uvx", uvx, "append");

 

[petz]

depending on the number of vertices, the easiest method is most probably using setdetailattrib() like in f1's second example. however, for very dense meshes and if performance is important it's better to iterate over the vertices and resize the array in advance instead of appending in a loop. this way you avoid continuous bounds checking of the array.

int num = detailintrinsic(@OpInput1, "primitivecount");
f[]@val_array;
resize(@val_array, num);
for(int i = 0; i < num; i++)
    @val_array[i] = vector(vertex(@OpInput1, "uv", i)).y;

hth.

petz

[Iraklo]

@petz @f1480187

  Thanks again guys. Much appreciated.