randomly distribute objects over a plane

Question

I have a number of different objects (e.g. cube, cylinder, monkey, furniture, etc) which I would like to distribute randomly over a plane/surface (the floor in this case) without having any intersections between the objects themselves as well as the wall. The objects there is no problem to be rotated so that they fit the "room" structure.

From a quick view I noticed people suggesting using the particles operator or the randomize transform. Would any of these alternatives work? I would like to do this in a python script.

Testing sample/example:

This is the file with furniture that I would like to position over the floor plane in random positions:

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Update:

It seems that using the randomize transform I can move the objects around the scene:

import bpy,random
from math import *

for obj in bpy.context.selected_objects:
    bpy.ops.object.randomize_transform(random_seed =random.randint(0,100), loc=(2, 2, 0), scale=(1, 1, 1))

The problem now is how to specify that I want the objects to be only within the borders of the floor (or the wall) object. I was thinking to specify loc= to the limits of the the bounding box of the floor but this will not handle the extruded parts. So there is the possibility that the moved object will be outside or intersecting to the wall. Moreover, from what I've noticed the randomize transform does not handle intersections thus this is also something that I would need to address.

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Update 2:

Based on the script from @james_t below as well as from this answer I've created the following solution:

import bpy,random
from math import *
from mathutils.bvhtree import BVHTree

import bmesh
import numpy as np
from mathutils import Vector

def numpy_apply_transforms(ob, co):
    m = np.array(ob.matrix_world)    
    mat = m[:3, :3].T 
    loc = m[:3, 3]
    return co @ mat + loc

def are_inside(points, bool_name, boundary='inside'):
    """
    input: 
        points
        - a list of vectors (can also be tuples/lists)
        bm
        - a manifold bmesh with verts and (edge/faces) for which the 
          normals are calculated already. (add bm.normal_update() otherwise)
    returns:
        a list
        - a mask lists with True if the point is inside the bmesh, False otherwise
    """

    
    rpoints = []
    addp = rpoints.append
    
    target_object = bpy.context.object
    bool_object   = bpy.data.objects[bool_name]

    #create mesh data
    bm = bmesh.new()
    bm.from_mesh(bool_object.data)
    bmesh.ops.transform(bm, matrix=bool_object.matrix_world, verts=bm.verts) #local to global coord
    bm.verts.ensure_lookup_table()
    bm.edges.ensure_lookup_table()
    bm.faces.ensure_lookup_table()
    bvh = BVHTree.FromBMesh(bm, epsilon=0.0001)
    
    points = numpy_apply_transforms(target_object, points) #local to global coord

    # return points on polygons
    for point in points:
        fco, normal, _, _ = bvh.find_nearest(point)
        p2 = fco - Vector(point)
        v = p2.dot(normal)
        if boundary == 'outside':
            addp(not v < 0.0) # addp(v >= 0.0) ?
        else:    
            addp(v < 0.0)

    return rpoints

obj_list = ['IKEA_bed_LEIRVIK', 'IKEA_chair_MARKUS']

#print(bpy.data.objects['Wall'].dimensions.x)
#print(bpy.data.objects['Wall'].dimensions.y)

for obj in obj_list:    
    obj = bpy.context.scene.objects.get(obj)
    bpy.context.view_layer.objects.active = obj
    if obj: obj.select_set(True)
    
    maxIter = 5
    placed = False

    print("Object: {}".format(obj.name))
    print( "origLocation: {}".format(obj.location) )
    
    while(not placed):
        print("Iteration: {}".format(maxIter))
        
        if maxIter < 0:
            print("gave up!!!")
            break
        
        # set object back to original location on each loop, to try again from that loc:
        obj.location.x = bpy.data.objects['Floor'].location.x
        obj.location.y = bpy.data.objects['Floor'].location.y
        
        print( "startingLocation: {}".format(obj.location) )
        
        # put object in new location
        bpy.ops.object.randomize_transform( random_seed =random.randint(0,100), use_loc=True, loc=(bpy.data.objects['Floor'].dimensions.x/2, bpy.data.objects['Wall'].dimensions.y/2, 0.0), scale=(1, 1, 1))
        
        print( "newLocation: {}".format(obj.location) )
        
        # Check if object is out of wall boundary
        rvalAry = are_inside(obj.bound_box, "Wall")
        print(rvalAry)
        
        if all(rvalAry):
            
            # Check if object is colliding with other objects
            for ob in obj_list:
                ob = bpy.context.scene.objects.get(ob)
                if obj == ob:
                    continue
                
                rvalAry_ = are_inside(obj.bound_box, ob.name, 'outside')
                print(rvalAry_)
                
                if not any(rvalAry_):
                    print("Object placed!!!")
                    placed = True
            
        maxIter -= 1
    bpy.ops.object.select_all(action='DESELECT') # Deselect all objects

This seems to work perfectly for putting the objects within the wall boundaries in first place. However, for some reason it still gives a fail while the objects are within the wall boundary and not colliding to each other (for simplicity I just considered only two objects and set the maxIter=5 this should be enough to have an example showing up) which I do not understand why. What am I missing?

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Update 3:

I've managed to solve the object overlapping with the following function:

def intersection_check(target_name, bool_name):
    
    target_object = bpy.data.objects[target_name]
    bool_object   = bpy.data.objects[bool_name]
    
    #create mesh data
    bm = bmesh.new()
    bm.from_mesh(target_object.data)
    bmesh.ops.transform(bm, matrix=target_object.matrix_world, verts=bm.verts) #local to global coord
    bm.verts.ensure_lookup_table()
    bm.edges.ensure_lookup_table()
    bm.faces.ensure_lookup_table()
    bvh = BVHTree.FromBMesh(bm, epsilon=0.0001)
    
    #create mesh data
    bm1 = bmesh.new()
    bm1.from_mesh(bool_object.data)
    bmesh.ops.transform(bm1, matrix=bool_object.matrix_world, verts=bm1.verts) #local to global coord
    bm1.verts.ensure_lookup_table()
    bm1.edges.ensure_lookup_table()
    bm1.faces.ensure_lookup_table()
    bvh1 = BVHTree.FromBMesh(bm1, epsilon=0.0001)
    
    if bvh.overlap( bvh1 ):
        return True
    else:
        return False

and then replacing the corresponding part from the previous update code snippet with the following:

            # Check if object is colliding with other objects
            rvalAry_ = []
            for ob in obj_list:
                ob = bpy.context.scene.objects.get(ob)
                if obj == ob:
                    continue
                
#                rvalAry_ = are_inside(obj.bound_box, ob.name, 'outside')
                rvalAry_.append( intersection_check(obj.name, ob.name) )
                print(rvalAry_)
                
            if not any(rvalAry_):
                print("Object placed!!!")
                placed = True

so far it seems to work ok.

Answer 1

Here is perhaps a solution, using the closest_point_on_mesh operation. I just enhanced to test the extreme vertices (bound_box) on the object being placed to be sure that it is placed completely within the floor bounds. I tested with on odd shaped floor (not just a rectangle plane). Note that this solution assumes that the floor has many vertices (subdivide if not) so that the locality test (closest_point_on_mesh()) is accurate. One problem I could not solve was that

# set object back to original location on each loop, to try again from that loc:
    obj.location = origLocation

was being ignored so I changed it to = floor.location.[xy] in the following code:

for obj in bpy.context.selected_objects:
    maxIter = 50
    placed = False
    #origLocation = obj.location
    #print( obj.location )
    print( "obj.dimensions=" )
    print( obj.dimensions )
    origLocation = obj.location
    print( "origLocation" )
    print( origLocation )
    while ( not placed ):
        print( maxIter )
        # set object back to original location on each loop, to try again from that loc:
        obj.location.x = floor.location.x
        obj.location.y = floor.location.y
        print( "obj.location=" )
        print( obj.location )
        bpy.ops.object.randomize_transform( random_seed =random.randint(0,100), use_loc=True, loc=(0.5, 0.5, 0.0), scale=(1, 1, 1))
        # check all boundary points:
        locatn = obj.location
        print( "new location=" )
        print( locatn )
        placed = True  # if any bounds are outside the floor plan, then reject (set to false)
        for bb in obj.bound_box:
            locatn.x = obj.location.x + bb[0]
            locatn.y = obj.location.y + bb[1]
            rvalAry = floor.closest_point_on_mesh( locatn, distance=0.1 )
            if ( not rvalAry[0] ): 
                placed = False
        maxIter -= 1
        if ( (maxIter < 0) or (placed) ) :
            placed = True
            if ( maxIter < 0 ):
                print( "gave up" )
                obj.location = origLocation
            else:                
                print( "placed" )
                print( obj.location )        
    print( obj.location )