2.91 Python API No change after applying boolean modifier operator

Question

How do I 'Apply' the Boolean Difference operation? I've written some Python that creates a hollow object visually, but in fact is not hollow. Visually I get the right thing:

Exporting to STL still has both objects (not an empty shell). I can manually complete the application of the Boolean operation by "Applying"

and deleting the inner object. Then the export to STL file is correct.

Here is the code I wrote, can someone let me know what calls I can make to apply the boolean modifier action and delete the object I used to cut into the other object with?

import sys
import bpy
D = bpy.data
C = bpy.context
from mathutils import *
import math
bpy.app.debug=True
########################################################################
Stitch together vertices to create a face in the arc
def face(column, row, columns, rows):
   v3 = ((column + 1) * rows) + row
   v3 = (((v3 // 4) * 4) + (v3 + 1) % 4)
   v4 = (column * rows + 1) + row
   v4a =  (((v4 // 4) * 4) + (v4) % 4)
   if v4a == v3:
      v4 = v4a - 4
   return (column* rows + row,
           (column + 1) * rows + row,
           v3,
           v4)
########################################################################
Create an arc, start and eng angle, a scale to convert units, inner/outer size, height and the number of segments
def arc_segment(nme, start_ang, end_ang, scale, outer_size, inner_size, height, segs):
Assuming arguments are in centimeters and in degrees, adjust o meters and radians.
Change from degrees to radians
start_ang = (math.tau / 360.0) * start_ang
   end_ang = (math.tau / 360.0) * end_ang
   if start_ang > end_ang:
      start_ang, end_ang = end_ang, start_ang
Change from meters (unit of measure in Blender) to centimeters
outer_size = scale * outer_size
   inner_size = scale * inner_size
We're creating the arc, beginning with the newmericly smaller angle.
if outer_size < inner_size:
      outer_size, inner_size = inner_size, outer_size
Arc will be created withe center at 0, 1/2 infront and 1/2 behing X/Y plane
height = scale * height
Use z for "height", center is 0, so 1/2 height away (plus), and 1/2 height close (minus)
p_height = (height * 0.5)
   m_height = (height * -0.5)
Think of the arc as a tube. This loop connects the faces to create the tube.
verts = []
   for seg in range(0, segs + 1):
      verts.append((math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,
                    math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,    p_height))
      verts.append((math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,
                    math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,    m_height))
      verts.append((math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,
                    math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,    m_height))
      verts.append((math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,
                    math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,    p_height))
sides = 4
   args = (segs, sides)
   faces = [face(x, y, segs, sides) for x in range(segs) for y in range(sides)]
Now cap the ends of the tube
faces.append((0, 1, 2, 3))
   vbase = segs * sides
   faces.append((vbase + 3, vbase + 2, vbase + 1, vbase))
Create object, link it into the scene, make it 'active'.
mesh_data = bpy.data.meshes.new(nme)

   mesh_data.from_pydata(verts, [], faces)

   mesh_data.update() # (calc_edges=True) not needed here
cube_object = bpy.data.objects.new(nme, mesh_data)
scene = bpy.context.scene

   bpy.context.collection.objects.link(cube_object)
   cube_object.select_set(state=True)
########################################################################
Solids modeling (CSG) take away coliding parts of one shape from another.
def csg(prim, cut, new_name, objects, operation):
   o_prim = objects[prim]
   o_cut = objects[cut]
   cut_work = o_prim.modifiers.new(type="BOOLEAN", name=new_name)
   cut_work.object = o_cut
   cut_work.operation = 'DIFFERENCE'
   o_cut.hide_set(True)                 # Hidden--But will still exist in an STL export.
--  --  --  --  --  --  --  --  --  --  --  --  --
What calls do I add here to "apply" the "difference" and delete the o_cut object?
--  --  --  --  --  --  --  --  --  --  --  --  --
########################################################################

objects = bpy.data.objects
set_scale = 2.54 * 2

Create some arcs
arc_segment("big_display_hull", 5.0, 90.0, set_scale, 11.5, 8.0, 4.5, 34)
arc_segment("big_hollow_hull", 6.5, 88.5, set_scale, 11.6, 7.7, 4.1, 34)
csg("big_display_hull", "big_hollow_hull", "o1", objects, 'DIFFERENCE')
arc_segment("attach_hulls",        360 + 110, 360 - 110.0, set_scale, 9.0, 8.0, 4.9, 120)
arc_segment("attach_hollow_hulls", 360 + 113, 360 - 113.0, set_scale, 9.2, 7.9, 4.1, 120)
csg("attach_hulls", "attach_hollow_hulls", "o3", objects, 'DIFFERENCE')
arc_segment("small_display_hull", 360 - 10, 360 - 65, set_scale, 11.5, 8.0, 4.5, 22)
arc_segment("small_hollow_hull", 360 - 11.5, 360 - 63.5, set_scale, 11.6, 7.7, 4.1, 22)
csg("small_display_hull", "small_hollow_hull", "o3", objects, 'DIFFERENCE')

I did try a suggested solution Scripting:How to correctly add a boolean modifer to an object? , after fixing a "'apply_as' unrecognized" issue, it ran. However I see that the boolean is still not applied. Given that blender 2.90.1 is so different than v 2.79, can someone post a complete python Boolean (CSG) example where the resulting meshes are the 'finished' objects? -- Also, I saw that 2.91 (beta) has something called 'exact solver', could someone post similar code to use the "exact solver"?

Hi and welcome! I think that's well explained in the linked answer. If you run into other issues, just let us know. — brockmann, Oct 06 '20 at 07:02
Tried the referenced, but after fixing "'apply_as' unrecognized" issue, I see that the boolean is still not applied. given that 2.90.1 is so different, can someone post a complete python Boolean (CSG) example where the model only has the 'finished' objects?

Also, I saw that 2.91 (beta) has something called 'exact solver', could someone post the code to use the "exact solver"? — Toby Baden, Nov 01 '20 at 02:10
Very borderline, have re-opened and answered. Main issue was assigning an active object for the operator. — batFINGER, Nov 02 '20 at 05:54

batFINGER · Answer 1 · 2020-11-02T05:44:31.157

Turn on developer extras / use autocomplete in the console.

Please use 4 space indent (not 3).
As noted the apply modifier no longer has an "apply_as" property.

For the exact solver set the solver attribute to exact, which is the default value anyway. Turn on developer extras in user prefs to get a tooltip displaying this, or use auto-complete in the console.

 >>> C.object.modifiers['o1']
 bpy.data.objects['big_display_hull'].modifiers["o1"]
>>> C.object.modifiers['o1'].solver
 'EXACT'
>>> C.object.modifiers['o1'].solver = 'FOO'
 Traceback (most recent call last):
   File "<blender_console>", line 1, in <module>
 TypeError: bpy_struct: item.attr = val: enum "FOO" not found in ('FAST', 'EXACT')

Operators work on the active and selected object(s). Have overridden the operator such that the active object is the prim. Can set the active object with context.view_layer.objects.active = ob (You were only selecting)
The apply modifier operator will fail silently, test run active object has no modifiers
```
 >>> bpy.ops.object.modifier_apply()
 {'CANCELLED'}
```
Remove any object with bpy.data.objects.remove(ob) This has been well documented and answered here

Changes for 2.91 using exact solver. There is no need to set as it is the default when modifier added

def csg(prim, cut, new_name, objects, operation):
   o_prim = objects[prim]
   o_cut = objects[cut]
   cut_work = o_prim.modifiers.new(type="BOOLEAN", name=new_name)
   cut_work.object = o_cut
   cut_work.operation = 'DIFFERENCE'
   o_cut.hide_set(True)                 # Hidden--But will still exist in an STL export.
   # --  --  --  --  --  --  --  --  --  --  --  --  --
   # What calls do I add here to "apply" the "difference" and delete the o_cut object?
   #cut_work.solver = 'EXACT' # it's the default anyhow.
   bpy.ops.object.modifier_apply(
      {"object" : o_prim},
      modifier=cut_work.name,
      )
   # --  -

Result of running with changes above.

High orange area is z-fighting between "big display hull" and "attach hulls"

I'd love to know how to apply a collection to the modifier, now that's a thing in 2.92 — Konchog, Mar 28 '21 at 17:40

Toby Baden · Answer 2 · 2020-11-04T16:52:50.240

Got it!

The main goal is now solved: an STL file that looks the same as in Blender. The corrected code is below.

The Boolean DIFFERENCE modifier runs successfully--Apparently it can "quietly" fail. <Any insight on getting more info on this?>
Once an object is used to cut away "material", the code deletes it successfully now.
Code now uses the implication that a modifier is created "as a child" of the currently active object

import sys
import bpy
D = bpy.data
C = bpy.context
from mathutils import *
import math
bpy.app.debug = True
########################################################################
Stitch together vertices to create a face in the arc
def face(column, row, columns, rows):
    v3 = ((column + 1) * rows) + row
    v3 = ((v3 // 4) * 4) + (v3 + 1) % 4
    v4 = (column * rows + 1) + row
    v4a = ((v4 // 4) * 4) + (v4) % 4
    if v4a == v3:
        v4 = v4a - 4
    return (column * rows + row, (column + 1) * rows + row, v3, v4)
########################################################################
Create an arc, start and eng angle, a scale to convert units, inner/outer size, height and the number of segments
def arc_segment(nme, start_ang, end_ang, scale, outer_size, inner_size, height, segs):
    # Assuming arguments are in centimeters and in degrees, adjust o meters and radians.
    # Change from degrees to radians
    start_ang = (math.tau / 360.0) * start_ang
    end_ang = (math.tau / 360.0) * end_ang
    if start_ang > end_ang:
        start_ang, end_ang = end_ang, start_ang
# Change from meters (unit of measure in Blender) to centimeters
outer_size = scale * outer_size
inner_size = scale * inner_size

# We're creating the arc, beginning with the newmericly smaller angle.
if outer_size &lt; inner_size:
    outer_size, inner_size = inner_size, outer_size

# Arc will be created withe center at 0, 1/2 infront and 1/2 behing X/Y plane
height = scale * height
# Use z for &quot;height&quot;, center is 0, so 1/2 height away (plus), and 1/2 height close (minus)
p_height = height * 0.5
m_height = height * -0.5

# Think of the arc as a tube. This loop connects the faces to create the tube.
verts = []
for seg in range(0, segs + 1):
    verts.append(
        (
            math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,
            math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,
            p_height,
        )
    )
    verts.append(
        (
            math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,
            math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * inner_size,
            m_height,
        )
    )
    verts.append(
        (
            math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,
            math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,
            m_height,
        )
    )
    verts.append(
        (
            math.cos(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,
            math.sin(start_ang + (end_ang - start_ang) * (seg / segs)) * outer_size,
            p_height,
        )
    )

sides = 4
args = (segs, sides)
faces = [face(x, y, segs, sides) for x in range(segs) for y in range(sides)]

# Now cap the ends of the tube
faces.append((0, 1, 2, 3))
vbase = segs * sides
faces.append((vbase + 3, vbase + 2, vbase + 1, vbase))

# Create object, link it into the scene, make it 'active'.
mesh_data = bpy.data.meshes.new(nme)
mesh_data.from_pydata(verts, [], faces)
mesh_data.update()  # (calc_edges=True) not needed here

cube_object = bpy.data.objects.new(nme, mesh_data)

scene = bpy.context.scene
bpy.context.collection.objects.link(cube_object)
cube_object.select_set(state=True)



########################################################################
Solids modeling (CSG) take away coliding parts of one shape from another.
The main corrections (the "answer") are in this method here:

def csg(prim, cut, new_name, objects, operation):
    o_prim = objects[prim]
    o_cut = objects[cut]
    bpy.context.view_layer.objects.active = o_prim   #Setting the primary object as active.
    cut_work = o_prim.modifiers.new(type="BOOLEAN", name=new_name)
    cut_work.object = o_cut
    cut_work.operation = "DIFFERENCE"
    o_cut.hide_set(True)  # Hidden--But will still exist in an STL export.
    rs = bpy.ops.object.modifier_apply({"object": cut_work.object}, modifier=cut_work.name)
    print(rs)   # If this quietly fails, this prints {'CANCELLED'}. How can one know what to fix? Maybe logs or something that can be looked at to find out why?
########################################################################

objects = bpy.data.objects
set_scale = 2.54 * 2

Create some arcs
arc_segment("big_display_hull", 5.0, 90.0, set_scale, 11.5, 8.0, 4.5, 34)
arc_segment("big_hollow_hull", 6.5, 88.5, set_scale, 11.6, 7.7, 4.1, 34)
csg("big_display_hull", "big_hollow_hull", "o1", objects, "DIFFERENCE")
arc_segment("attach_hulls", 360 + 110, 360 - 110.0, set_scale, 9.0, 8.0, 4.9, 120)
arc_segment(
    "attach_hollow_hulls", 360 + 113, 360 - 113.0, set_scale, 9.2, 7.9, 4.1, 120
)
csg("attach_hulls", "attach_hollow_hulls", "o2", objects, "DIFFERENCE")
arc_segment("small_display_hull", 360 - 10, 360 - 65, set_scale, 11.5, 8.0, 4.5, 22)
arc_segment("small_hollow_hull", 360 - 11.5, 360 - 63.5, set_scale, 11.6, 7.7, 4.1, 22)
csg("small_display_hull", "small_hollow_hull", "o3", objects, "DIFFERENCE")
```

Thanks to all who helped me connect the dots :-) – Toby Baden Nov 04 '20 at 22:55 — Toby Baden, Nov 04 '20 at 22:55

2.91 Python API No change after applying boolean modifier operator

Stitch together vertices to create a face in the arc

Create an arc, start and eng angle, a scale to convert units, inner/outer size, height and the number of segments

Assuming arguments are in centimeters and in degrees, adjust o meters and radians.

Change from degrees to radians

Change from meters (unit of measure in Blender) to centimeters

We're creating the arc, beginning with the newmericly smaller angle.

Arc will be created withe center at 0, 1/2 infront and 1/2 behing X/Y plane

Use z for "height", center is 0, so 1/2 height away (plus), and 1/2 height close (minus)

Think of the arc as a tube. This loop connects the faces to create the tube.

Now cap the ends of the tube

Create object, link it into the scene, make it 'active'.

Solids modeling (CSG) take away coliding parts of one shape from another.

-- -- -- -- -- -- -- -- -- -- -- -- --

What calls do I add here to "apply" the "difference" and delete the o_cut object?

-- -- -- -- -- -- -- -- -- -- -- -- --

Create some arcs

2 Answers2

Stitch together vertices to create a face in the arc

Create an arc, start and eng angle, a scale to convert units, inner/outer size, height and the number of segments

Solids modeling (CSG) take away coliding parts of one shape from another.

The main corrections (the "answer") are in this method here:

Create some arcs