matrix multiplication note to self

matrix multiplication, matrix * point using mathutils: using numpy: and three.js too

references

http://www.scipy.org/NumPy_for_Matlab_Users
http://docs.scipy.org/doc/numpy/reference/generated/numpy.matrix.html

matrix_world

This multiplies the coordinates as found in the object data with the world matrix of that object. Essentially giving the world coordinate of any selected vertex, even when the object origin is not at the world origin.

Further reading

• http://db-in.com/blog/2011/04/cameras-on-opengl-es-2-x/

ready to generate geometry - edge fillet blender 2.5

the code is a little lengthy to post in its entirety, but you can download it here

def get_correct_verts(arc_centre, arc_start, arc_end, NUM_VERTS, context):
        
    obj_centre = context.object.location
    axis = mathutils.geometry.normal(arc_centre, arc_end, arc_start)
 
    point1 = arc_start - arc_centre
    point2 = arc_end - arc_centre
    main_angle = point1.angle(point2)
    main_angle_degrees = math.degrees(main_angle)

    div_angle = main_angle / (NUM_VERTS - 1)

    if DEBUG == True:
        print("arc_centre =", arc_centre)
        print("arc_start =", arc_start)
        print("arc_end =", arc_end)
        print("NUM_VERTS =", NUM_VERTS)
    
        print("NormalAxis1 =", axis)
        print("Main Angle (Rad)", main_angle, " > degrees", main_angle_degrees)
        print("Division Angle (Radians)", div_angle)
        print("AXIS:", axis)
    
    trig_arc_verts = []

    for i in range(NUM_VERTS):
        rotation_matrix = mathutils.Matrix.Rotation(i*-div_angle, 3, axis)
        # trig_point = (arc_start - obj_centre - arc_centre) * rotation_matrix # old
        trig_point = rotation_matrix * (arc_start - obj_centre - arc_centre) # new
        trig_point += obj_centre + arc_centre
        trig_arc_verts.append(trig_point)        
        
    return trig_arc_verts

Matrix.Rotate() was the most complicated part, but now i've broken through that barrier it doesn't seem such utter voodoo anymore. Warning to user: you must apply scale/location/rotation transforms to your profile/object first before running the code or the vertices will appear somewhere else. Not sure if there is a cute way around that.

small update

blender 2.5 GL fillet v0.2 from zeffii stanton on Vimeo.