How To ... Select Non-Quad Polygons

How To > Select Non-Quad Polygons

MAXScript lets you access Editable Poly object data and explore relationships between polygons, vertices and edges. When using polygon modeling it is usually desirable that all polygons are kept as quads. The following script will select all polygons that have less or more than 4 edges.

Related Topics:

Defining and Enabling Macroscripts

Accessing Editable Polygon Data

Accessing the Modify Panel

NATURAL LANGUAGE

Package the code as macroScript to be able to use as a button, menu item or shortcut.

Enable only if a single object with an Editable Poly base object is selected.

When executed, get the base object of the selected object.

Go though all polygons of the base object and ask about their edges.

Count the edges and if they are not exactly 4, remember the index of the polygon.

Select all the non-quad polygons.

Go to Polygon Sub-Object Level in the Modify Tab.

MAXSCRIPT

macroscript SelectNonQuadPolys category: "HowTo"
(
on isEnabled return
(
 selection.count == 1 and classOf selection[1].baseobject == Editable_Poly
)
on execute do
(
 local face_selection = #{}
 local base_obj = $.baseobject
 local num_faces = polyop.getNumFaces base_obj
 for f = 1 to num_faces do
 (
  local num_face_verts = polyop.getFaceDeg base_obj f
  if num_face_verts != 4 do face_selection[f] = true
 )--end f loop
 polyop.setFaceSelection base_obj face_selection
 max modify mode
 modPanel.setCurrentObject base_obj
 subobjectlevel = 4
)--end on execute
)--end script

Step-By-Step

Macroscript SelectNonQuadPolys category:"HowTo"
(

The macroScript will be called SelectNonQuadPolys . To use the script, you can use Customize... to drag the script from the category "HowTo" to a toolbar, a menu, a quad menu or to assign to a keyboard shortcut.

Defining Macro Scripts

on isEnabled return
(
selection.count == 1 and classOf selection[1].baseobject == Editable_Poly
)

The isEnabled handler should return true or false and determines the enabled state of the button / menu item. When true , the button will be available. When false , it will be grayed out. In the return expression, we check whether only one object is selected in the scene and whether its base object class is Editable Poly. The script will only work on objects that meet both conditions.

ClassOf

General Node Properties

on execute do (

The on Execute handler will be executed each time the macroScript is executed (by pressing the button, selecting from the menu, pressing the shortcut etc.). The handler contains the "body" of the script.

Macroscript_Body_Event_Handlers

local face_selection = #{}

We will need a user variable to store the polygons to be selected. We initialize the variable to an empty BitArray

local base_obj = $.baseobject

Our script will work on the base object only. This means that the object may have modifiers on top of the base object – they will not be taken into account as polygon modeling usually happens at the base level anyway. Because we already made sure in the isEnabled handler that there is only a single object selected, we can access the selection using $ without worrying that it might contain multiple objects!

local num_faces = polyop.getNumFaces base_obj

We will need the number of faces in the object in order to iterate through them.

Editable_Poly Methods

for f = 1 to num_faces do
(

We will loop through all polygons in the base object – f will contain the index of the current polygon to be checked.

For Loop

local num_face_verts = polyop.getFaceDeg base_obj f

Next we get a the number of vertices in the current polygon.

Editable_Poly Methods

if num_face_verts != 4 do face_selection[f] = true

If the number of vertices is not 4, we should select the polygon so we set the respective bit in the bitArray corresponding to the current face to true.

Array Values

)--end f loop
polyop.setFaceSelection base_obj face_selection

After checking all polygons, we can simply select all collected polygons.

Editable_Poly Methods

max modify mode

In order to show the results of the selection to the user, we will first switch the command panel to modify mode...

MAX Commands

modPanel.setCurrentObject base_obj

...then set the current object in Stack View to the base object we checked...

Modify Panel

subobjectlevel = 4

...and finally switch to Polygon sub-object level to show the selected polygons.

subObjectLevel

)--end on execute
)--end script

Using the Script

To use the script, you can use Customize... to drag the script from the category "HowTo" to a toolbar, a menu, a quad menu or to assign to a keyboard shortcut. Select a single object with an Editable Poly base object and the script will be enabled. Execute and the non-quad polygons will become selected.

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