Command Name ?

[Arthur Spooner]

$YMAX + bbox("../box1/", D_YMAX)

This command is 1 + which is ontop of box1, how is that calculated ?

[f1480187]

$YMAX is topmost Y coordinate of input geometry. Same as bbox(opinputpath(".", 0), D_YMAX) but shorter and cleaner.
bbox("../box1/", D_YMAX) is topmost Y of box1 node. The whole thing can be written as:

bbox(opinputpath(".", 0), D_YMAX) + bbox("../box1/", D_YMAX)

Note that $YMAX will work only on transform node, it's a local variable. Expression function will work anywhere. Also note that $YMAX and D_YMAX are totally different things, first is an actual point Y value, the latter one of aforenamed eight "integers", used to determine result you need to get from a function.

Edited February 5, 2016 by f1480187

[Arthur Spooner]

Also note that $YMAX and D_YMAX are totally different things, first is an actual point Y value, the latter one of aforenamed eight "integers", used to determine result you need to get from a function

 

 

Sorry I didn't understand the latter of your explanation ?

 

$YMAX takes into consideration the top most of box1 when it's combined with anything ?

[f1480187]

$YMAX has no idea about box1. The one who consider it is bbox function with a path to that box. Both sides will evaluate to some float values before adding.

Edited February 5, 2016 by f1480187

[Arthur Spooner]

Both sides will evaluate to some float values before adding.

 

 

I don't understand how do both sides evaluate ?

[f1480187]

If you have no idea what variables and functions are, try to follow a starter's tutorial (sections 3 to 5) on Python's website. Houdini's Python Shell (Alt+Shift+p) is a typical Python interpreter, no need to install anything. If you talking about exact in-code implementation, probably only devs can answer this.

Edited February 5, 2016 by f1480187

[Arthur Spooner]

Do you know how to know what floating point values both sides evaluate too, if it's possible ?

Edited February 5, 2016 by Arthur Spooner

[michael]

a good read through the docs would really help here, and in the textport (Windows > HScript Textport) you can do:

/ -> exhelp -k bbox

will return

 

bbox     centroid 

 

"help -k somthing" or "exhelp -k something"= when you use the -k flag the command will return all the commands or functions that have the string after the -k in them

 

then you can do 

/ -> exhelp bbox

 

and you'll get 

float bbox (string surface_node, float type)

        Returns bounding box information for a surface node.

        

        USAGE

        

            bbox(<surface_node>, <type>)

        

            The <type> can be one of D_XMIN, D_YMIN, D_ZMIN, D_XMAX, D_YMAX,

            D_ZMAX, D_XSIZE, D_YSIZE, or D_ZSIZE for the corresponding values of

            the bounding box.

        

        RELATED

        

        

         *  centroid

 

D_XMIN etc refer to the dimentions of that component

for a 1 unit box sitting on the ground

D_YMIN = 0

D_YMAX = 1

D_XMIN = -0.5 (if the box is at the origin)

D_XMAX = 0.5

etc

 

the local variable $YMAX would in the above case refer to the maximum value in the Y dimension = 1

 

 

Houdini used to call a Transform node "xform"

now we actually call the node "transform"

but they are the same node

[Arthur Spooner]

That was helpful Michael.  In other words this $YMAX + bbox("../box1/", D_YMAX);

 

$YMAX + What do you call the path for bbox in Houdini, is it simply "path" ?

[f1480187]

1. You can click on the parameter's label to see exact field's values. However, will not work for anything using local vars currently, showing zeros. Ctrl+Shift+LMB on parameter will forcefully evaluate it to the true value. Try this for different parts of expression, e.g. for $YMAX or for bbox("../box1/", D_YMAX) alone, or even for D_YMAX.

 

2. bbox function returns a float, not a string with path. The path is what you provide with the first argument - a string looking like a path. Two dots means parent network of this node, so, it is a relative path similar to something absolute like /obj/geo1/box1. Then bbox function use that path and return a number to you. There are 8 possible floats can be returned, and second bbox's argument is used to determine it.

Edited February 6, 2016 by f1480187

[Arthur Spooner]

Try this for different parts of expression, e.g. for $YMAX or for bbox("../box1/", D_YMAX) alone, or even for D_YMAX.

 

 

Sorry, what do I try that is different, I have that expression in place ? 

 

What you are saying is; $YMAX is the interger and the path is a float ? How does bbox turn a path a return a float number ?

[f1480187]

Here.

evaluate.hipnc

[Arthur Spooner]

transform1 & transform 3 both have the same expression ? 

 

transform 2 doesn't do anything different ?

[f1480187]

1. $YMAX and D_YMAX may look similar in some way, but they are not the same things and the values are different (if there is no coincidence).

 

2. $YMAX and bbox(path_to_input, D_YMAX) may look different. But, actually, they are same resulting values.

 

$YMAX is topmost Y coordinate of input geometry. Same as bbox(opinputpath(".", 0), D_YMAX)

See the docs about the function returning path.

[Arthur Spooner]

From my understanding in the path ("../box1/")

 

"box1"

   1

 

If you were to add another box or sphere or what have you that would be

 

"box2"

    2

 

Sorta like an array ?