Parametric custom objects with Python

So, Blender 2.44 is out and one of the best news for me was that it is now possible to add custom objects to Add-menu with Python. This is a short overview of how this can be done.

Parametric Plane-object

Let's make a Blender's plane object but now with user-defined size (width/height).

This is the start of the file. Name is the text shown in the Add-menu. Important part here is the group name: "AddMesh" defines that this script is shown in Add-menu.

#!BPY
"""
Name: 'MyVeryOWNObject'
Blender: 244
Group: 'AddMesh'
"""
import BPyAddMesh
import Blender

GUI

Before we write the actual mesh code, we can make the GUI ready and test it.

Let's start with main function:

#!BPY
"""
Name: 'MyVeryOWNObject'
Blender: 244
Group: 'AddMesh'
"""
import BPyAddMesh
import Blender

def main():
	
	# Numeric input with default value of 1
	planeWidthInput = Blender.Draw.Create(1.0)
	
	# and same for height
	planeHeightInput  = Blender.Draw.Create(1.0)

	# array for popup window's content	
	block = []
	
	# add inputs to array with title, min/max values and tooltip
	block.append(("width: ", planeWidthInput, 0.01, 100, "width of the plane"))
	block.append(("height: ", planeHeightInput, 0.01, 100, "height of the plane"))
	
	# draw	popup if it is not open allready 
	if not Blender.Draw.PupBlock("Create plane",block):
		return

#let's call main
main()

When you run this (Alt + P), you should see something like this:

Now we can add the actual geometry code.

Geometry code

For plane, the geometry code is really simple. Just add four points (xyz) to a vertices array and then add their indexes to a face array and return both.

def add_mymesh(PREF_WIDTH, PREF_HEIGHT):

	verts = []
	faces = []
		

	verts.append([-(PREF_WIDTH/2),(PREF_HEIGHT/2),0.0])
	verts.append([-(PREF_WIDTH/2),-(PREF_HEIGHT/2),0.0])
	verts.append([(PREF_WIDTH/2),-(PREF_HEIGHT/2),0.0])
	verts.append([(PREF_WIDTH/2),(PREF_HEIGHT/2),0.0])
	
	faces.append([0,1,2,3])
	
	return verts, faces

Then we just call that from popup function.

verts, faces = add_mymesh(planeWidthInput.val, planeHeightInput.val)

And just one line more and we are finished. This creates the actual Blender object and puts that to the scene:

BPyAddMesh.add_mesh_simple('MyPlane', verts, [], faces) 

NOTE: BPyAddMesh is from experimental Python api that is about to change without warning!

Whole code

#!BPY
"""
Name: 'MyVeryOWNObject'
Blender: 244
Group: 'AddMesh'
"""
import BPyAddMesh
import Blender

def add_mymesh(PREF_WIDTH, PREF_HEIGHT):

	verts = []
	faces = []
		
	verts.append([-(PREF_WIDTH/2),(PREF_HEIGHT/2),0.0])
	verts.append([-(PREF_WIDTH/2),-(PREF_HEIGHT/2),0.0])
	verts.append([(PREF_WIDTH/2),-(PREF_HEIGHT/2),0.0])
	verts.append([(PREF_WIDTH/2),(PREF_HEIGHT/2),0.0])
	
	faces.append([0,1,2,3])
	
	return verts, faces

def main():
	
	# Numeric input with default value of 1
	planeWidthInput = Blender.Draw.Create(1.0)
	
	# and same for height
	planeHeightInput  = Blender.Draw.Create(1.0)

	# array for popup window's content	
	block = []
	
	# add inputs to array with title, min/max values and tooltip
	block.append(("width: ", planeWidthInput, 0.01, 100, "width of the plane"))
	block.append(("height: ", planeHeightInput, 0.01, 100, "height of the plane"))
	
	# draw	popup if it is not open allready 
	if not Blender.Draw.PupBlock("Create plane",block):
		return
	
	verts, faces = add_mymesh(planeWidthInput.val, planeHeightInput.val)
	
	BPyAddMesh.add_mesh_simple('MyPlane', verts, [], faces)

main()