Add more Python scrap code from Blender

blender_scraps/scratch.py

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+# This is a pile of patterns and snippets I've used in Blender in the
+# past; it isn't meant to be run on its own.
+
+import bmesh
+import bpy
+
+# Here is a good starting place (re: creating geometry):
+# https://docs.blender.org/api/current/info_gotcha.html#n-gons-and-tessellation
+
+# https://wiki.blender.org/wiki/Source/Modeling/BMesh/Design
+
+# Current object's data (must be selected):
+me = bpy.context.object.data
+
+def bmesh_set_creases(obj, vert_pairs, crease_val):
+    # Walk through the edges in 'obj'. For those *undirected* edges in
+    # 'vert_pairs' (a set of (vi, vj) tuples, where vi and vj are vertex
+    # indices, and tuple order is irrelevant), set the crease to 'crease_val'.
+    bm = bmesh.new()
+    bm.from_mesh(obj)
+    creaseLayer = bm.edges.layers.crease.verify()
+    for e in bm.edges:
+        idxs = tuple([v.index for v in e.verts])
+        print(idxs)
+        if idxs in vert_pairs or idxs[::-1] in vert_pairs:
+            e[creaseLayer] = crease_val
+    bm.to_mesh(obj)
+    bm.free()
+
+# My bpy.types.MeshPolygon objects:
+for i,poly in enumerate(me.polygons):
+    t = type(poly)
+    #print(f"poly {i}: {t}")
+    verts = list(poly.vertices)
+    print(f"poly {poly.index}: vertices={verts}")
+    #s = poly.loop_start
+    #n = poly.loop_total
+    #print(f"  loop_start={s} loop_total={n}")
+    #v = [l.vertex_index for l in me.loops[s:(s+n)]]
+    #print(f"  loop: {v}")
+    # Vector type:
+    v2 = [me.vertices[i].co for i in verts]
+    print(f"  verts: {v2}")
+    # Yes, this works:
+    #for i in verts:
+    #    me.vertices[i].co.x -= 1.0
+
+# Pattern for loading external module from Blender's Python (and
+# reloading as necessary):
+import sys
+ext_path = "/home/hodapp/source/automata_scratch/blender_scraps"
+if ext_path not in sys.path:
+    sys.path.append(ext_path)
+import whatever
+whatever = importlib.reload(whatever)
+# Note that if 'whatever' itself imports modules that may have changed
+# since the last import, you may need to do this same importlib
+# incantation!
+
+# Crease access - but the wrong way to change them:
+for edge in me.edges:
+    v = list(edge.vertices)
+    print(f"edge {edge.index}: crease={edge.crease} vertices={v}")
+    #edge.crease = 0.7
+
+# Creating a mesh with vertices & faces in Python via bpy with:
+# v - list of (x, y, z) tuples
+# f - list of (v0, v1, v2...) tuples, each with face's vertex indices
+mesh = bpy.data.meshes.new('mesh_thing')
+mesh.from_pydata(v, [], f)
+mesh.update(calc_edges=True)
+# set creases beforehand:
+#bmesh_set_creases(mesh, b.creases_joint, 0.7)
+obj = bpy.data.objects.new('obj_thing', mesh)
+# set obj's transform matrix:
+#obj.matrix_world = Matrix(...)
+# also acceptable to set creases:
+#bmesh_set_creases(obj.data, b.creases_joint, 0.7)
+bpy.context.scene.collection.objects.link(obj)