Add session 12 - 2020

meetings/2020/session_12_python_and_blender/README.md

+# Python and Blender
+
+In this session Kimberly Meechan introduced how she uses Blender (https://blender.org) in her scientific projects.
+
+The files used in this session can be found at: https://git.embl.de/meechan/blender_intro
+
+A slightly more advanced example is included in this repository (see `cube_scrambler_panel.py`)

meetings/2020/session_12_python_and_blender/cube_scrambler_panel.py

+import bpy
+from math import radians, degrees, isclose
+import mathutils
+
+global current_frame
+current_frame = 1.0
+
+def update_keyframes():
+    global current_frame
+    current_frame += 1.0
+    for obj in bpy.data.objects:
+        obj.keyframe_insert(data_path="location", frame=current_frame)
+        obj.keyframe_insert(data_path="rotation_quaternion", frame=current_frame)
+
+def rotate_about_centre(cubie, centre_cube, angle, axis):
+    
+#    Deal with cubie location
+#    Translate to centre, rotate, and translate back
+    rotation_centre = centre_cube.location
+    translate_to_centre = mathutils.Matrix.Translation(rotation_centre - cubie.location)
+    rotation = mathutils.Matrix.Rotation(radians(angle), 4, axis)
+    translate_back = translate_to_centre.copy()
+    translate_back.invert()
+    full_matrix =  translate_to_centre @ rotation @ translate_back
+    cubie.location = cubie.location + full_matrix.to_translation()
+    
+#    Deal with cubie rotation, using quaternions
+    if axis == 'X':
+        axis_vector = (1.0,0.0,0.0)
+    elif axis == 'Y':
+        axis_vector = (0.0,1.0,0.0)
+    elif axis == 'Z':
+        axis_vector = (0.0,0.0,1.0)
+    
+    cubie.rotation_mode = 'QUATERNION'
+    cubie.rotation_quaternion = mathutils.Quaternion(axis_vector, radians(angle)) @ cubie.rotation_quaternion 
+    
+def rotate_cube(command, cubie, centre_cube, angle):
+    
+    if command == "F":
+        rotate_about_centre(cubie, centre_cube, angle, 'Y')
+           
+    elif command == "F'":
+        rotate_about_centre(cubie, centre_cube, -angle, 'Y')
+        
+    if command == "L":
+        rotate_about_centre(cubie, centre_cube, angle, 'X')
+           
+            
+    elif command == "L'":
+        rotate_about_centre(cubie, centre_cube, -angle, 'X')
+
+    if command == "R":
+        rotate_about_centre(cubie, centre_cube, -angle, 'X')
+           
+            
+    elif command == "R'":
+        rotate_about_centre(cubie, centre_cube, angle, 'X')
+        
+    if command == "B":
+        rotate_about_centre(cubie, centre_cube, -angle, 'Y')
+            
+    elif command == "B'":
+        rotate_about_centre(cubie, centre_cube, angle, 'Y')
+        
+    if command == "U":
+        rotate_about_centre(cubie, centre_cube, -angle, 'Z')
+           
+            
+    elif command == "U'":
+        rotate_about_centre(cubie, centre_cube, angle, 'Z')
+        
+    if command == "D":
+        rotate_about_centre(cubie, centre_cube, angle, 'Z')
+           
+    elif command == "D'":
+        rotate_about_centre(cubie, centre_cube, -angle, 'Z')
+
+def rotate_face(command, centre_cube, paired_cubes): 
+    for i in range(0, 45):
+         
+        for cubie in paired_cubes:
+            rotate_cube(command, cubie, centre_cube, 2)
+        rotate_cube(command, centre_cube, centre_cube, 2) 
+        update_keyframes()
+    
+
+def find_face (command):
+    centre_cube = None
+    paired_cubes = []
+    
+#    Distance tolerance for matching cube locations
+    tol =1e-4
+    
+    for cube in bpy.data.collections['Cubies'].all_objects:        
+        if command == "F" or command == "F'":
+                if isclose(cube.location.y, -2, abs_tol=tol) and isclose(cube.location.x, 0, abs_tol=tol) and isclose(cube.location.z, 0, abs_tol=tol):
+                    centre_cube = cube
+                elif isclose(cube.location.y, -2, abs_tol=tol):
+                    paired_cubes.append(cube)
+                    
+        if command == "R" or command == "R'":
+            if isclose(cube.location.y, 0, abs_tol=tol) and isclose(cube.location.x, 2, abs_tol=tol) and isclose(cube.location.z, 0, abs_tol=tol):
+                centre_cube = cube
+            elif isclose(cube.location.x, 2, abs_tol=tol):
+                paired_cubes.append(cube)
+                    
+        if command == "L" or command == "L'":
+            if isclose(cube.location.y, 0, abs_tol=tol) and isclose(cube.location.x, -2, abs_tol=tol) and isclose(cube.location.z, 0, abs_tol=tol):
+                centre_cube = cube
+            elif isclose(cube.location.x, -2, abs_tol=tol):
+                paired_cubes.append(cube)
+                    
+        if command == "B" or command == "B'":
+            if isclose(cube.location.y, 2, abs_tol=tol) and isclose(cube.location.x, 0, abs_tol=tol) and isclose(cube.location.z, 0, abs_tol=tol):
+                centre_cube = cube
+            elif isclose(cube.location.y, 2, abs_tol=tol):
+                paired_cubes.append(cube)
+                    
+        if command == "U" or command == "U'":
+            if isclose(cube.location.y, 0, abs_tol=tol) and isclose(cube.location.x, 0, abs_tol=tol) and isclose(cube.location.z, 2, abs_tol=tol):
+                centre_cube = cube
+            elif isclose(cube.location.z, 2, abs_tol=tol):
+                paired_cubes.append(cube)
+                    
+        if command == "D" or command == "D'":
+            if isclose(cube.location.y, 0, abs_tol=tol) and isclose(cube.location.x, 0, abs_tol=tol) and isclose(cube.location.z, -2, abs_tol=tol):
+                centre_cube = cube
+            elif isclose(cube.location.z, -2, abs_tol=tol):
+                paired_cubes.append(cube)
+                
+    return centre_cube, paired_cubes
+    
+
+def rotate_whole_cube (command):
+    
+    centre_cube, paired_cubes = find_face(command)
+    
+    rotate_face(command, centre_cube, paired_cubes)
+    
+def scramble():
+    scramble_string = bpy.context.scene.cube_settings.scramble
+    bpy.context.scene.frame_set(1.0)
+    global current_frame
+    current_frame = 1.0
+
+    for obj in bpy.data.objects:
+        obj.animation_data_clear()
+        obj.keyframe_insert(data_path="location", frame=current_frame)
+        obj.keyframe_insert(data_path="rotation_quaternion", frame=current_frame)
+
+    for i in range(0, len(scramble_string)):
+        
+        command = scramble_string[i]
+        
+        if i+1 < len(scramble_string):
+            next_letter = scramble_string[i+1]
+        else:
+            next_letter = ""
+        
+        if command == "'":
+            continue
+        
+        if next_letter == "'":
+            command += next_letter
+        
+        rotate_whole_cube(command)
+    bpy.context.scene.frame_set(current_frame)
+        
+class scrambler_settings(bpy.types.PropertyGroup):
+    scramble: bpy.props.StringProperty(name = 'scramble', default="", description="sequence of moves to scramble cube")
+        
+class SCRAMBLER_PT_panel(bpy.types.Panel):
+    """Cube scrambler panel"""
+    bl_label = "Cube Scrambler"
+    bl_space_type = 'PROPERTIES'
+    bl_region_type = 'WINDOW'
+    bl_context = "object"
+    
+    def draw(self, context):
+        layout = self.layout
+        
+        row = layout.row()
+        row.label(text = 'Cube moves:')
+        row = layout.row()
+        row.prop(bpy.context.scene.cube_settings, 'scramble', text = 'moves')
+        
+        row = layout.row()
+        row.operator('object.scrambler_operator', text = 'Scramble!')
+        
+
+class SCRAMBLER_OT_operator (bpy.types.Operator):
+    """Scrambles cube"""
+    bl_idname = "object.scrambler_operator"
+    bl_label = "scrambles_cube"
+
+    def execute(self, context):
+        scramble()
+        return {'FINISHED'}
+    
+def register():
+    bpy.utils.register_class(SCRAMBLER_PT_panel)
+    bpy.utils.register_class(SCRAMBLER_OT_operator)
+    bpy.utils.register_class(scrambler_settings)
+    bpy.types.Scene.cube_settings = bpy.props.PointerProperty(type=scrambler_settings)
+
+
+def unregister():
+    bpy.utils.unregister_class(SCRAMBLER_PT_panel)
+    bpy.utils.unregister_class(SCRAMBLER_OT_operator)
+    bpy.utils.unregister_class(scrambler_settings)
+
+
+if __name__ == "__main__":
+    register()
+    
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