figure 1. shows circle obtain from 3 verts minimum.

The following code is the least bit of code you need to get the circle center from 3 verts using trig.

### Missing convenience for semi high precision modelling

Periodically I miss the most elementary CAD features in Blender. While Blender is not designed for ultra high precision modeling, there's still room for precision before resorting to simply "eye-balling" it. Core developers are busy making Blender awesome in other ways, so instead of sidetracking them I like to experiment and learn how to make these tools myself. Whatever, I just need this stuff and don't want to wait.### Additions to tinyCAD

Blender doesn't keep track of origins / centers of its primitives. For circles, let's not beat around the bush, this is highly annoying. Once you edit or move a circle mesh you lose the ability to change its parameters. Often I need to find the center of a circle after some of its vertices have been deleted. If you still have 3 points, the origin can be found easily using trigonometry. I'll add this to the tinyCAD. My implementation will work on either selecting two adjacent edges, or 3 vertices (not necessarily adjacent)### edit

This is now added to the github version as 'Circle Centers', prior to updating the addons/contrib version.The following code is the least bit of code you need to get the circle center from 3 verts using trig.

import bpy import bmesh import math import mathutils from mathutils import geometry from mathutils import Vector def generate_3PT_mode_1(pts=[]): verts, edges = [], [] V = Vector # construction v1, v2, v3, v4 = V(pts[0]), V(pts[1]), V(pts[1]), V(pts[2]) edge1_mid = v1.lerp(v2, 0.5) edge2_mid = v3.lerp(v4, 0.5) axis = geometry.normal(v1, v2, v4) mat_rot = mathutils.Matrix.Rotation(math.radians(90.0), 4, axis) # triangle edges v1_ = ((v1 - edge1_mid) * mat_rot) + edge1_mid v2_ = ((v2 - edge1_mid) * mat_rot) + edge1_mid v3_ = ((v3 - edge2_mid) * mat_rot) + edge2_mid v4_ = ((v4 - edge2_mid) * mat_rot) + edge2_mid r = geometry.intersect_line_line(v1_, v2_, v3_, v4_) if r: # for general use this requires: matrix_local * p1 p1, _ = r bpy.context.scene.cursor_location = p1 else: print('not on a circle') return verts, edges def get_three_verts_from_selection(obj): me = obj.data bm = bmesh.from_edit_mesh(me) if hasattr(bm.verts, "ensure_lookup_table"): bm.verts.ensure_lookup_table() bm.edges.ensure_lookup_table() return [v.co[:] for v in bm.verts if v.select] obj = bpy.context.object pts = get_three_verts_from_selection(obj) generate_3PT_mode_1(pts)

Thanks for all you of effort. Now I'm making some tools too... may be you want to add this for your tinyCAD. http://blenderartists.org/forum/showthread.php?358416-Addon-perpendicular-bisector. Thanks for all.

ReplyDeleteDiego QUEVEDO.

PD I, from my gf tablet :D

Hi Diego,

DeleteUnfortunately I think extra perpendicular cuts are not what tinyCAD needs. I might even remove the current PERP mode in tinyCAD because I never use it.