Python - Groups - Finding the Normal on a Child Object(Convert a Point from World Space to Object Space)

The Ray Tracer Challenge:
A Test-Driven Guide to Your First 3D Renderer
楽天 紀伊国屋書店

開発環境

• macOS Mojave - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Python 3.7 (プログラミング言語)
• GIMP (ビットマップ画像編集・加工ソフトウェア、PPM形式(portable pixmap)の画像用)

The Ray Tracer Challenge: A Test-Driven Guide to Your First 3D Renderer (Jamis Buck(著)、Pragmatic Bookshelf)、Chapter 14(Groups)のFinding the Normal on a Child Object、Test #7(Convert a Point from World Space to Object Space)を取り組んでみる。

コード

shapes_test.py

#!/usr/bin/env python3
import math
from unittest import TestCase, main
from shapes import Shape
from transformations import translation
from matrices import IDENTITY_MATRIX, Matrix
from materials import Material
from rays import Ray
from tuples import Point, Vector
from transformations import scaling, rotation_y
from groups import Group
from spheres import Sphere


class ShapeTest(TestCase):
    def setUp(self):
        self.shape = Shape(material=Material())

    def tearDown(self):
        pass

    def test_default_transformation(self):
        self.assertEqual(self.shape.transform, IDENTITY_MATRIX)

    def test_material(self):
        self.assertEqual(self.shape.material.ambient, 0.1)
        self.assertEqual(self.shape.material, Material())

    def test_transform(self):
        self.assertEqual(Shape().transform,
                         IDENTITY_MATRIX)
        s = Shape()
        t = translation(2, 3, 4)
        s.transform = t
        self.assertEqual(s.transform, t)

    def test_parent_attribute(self):
        s = Shape()
        self.assertIsNone(s.parent)

    def test_converting_point_from_world_to_object_space(self):
        group1 = Group(transform=rotation_y(math.pi / 2))
        group2 = Group(transform=scaling(2, 2, 2))
        group1.add_child(group2)
        sphere = Sphere(translation(5, 0, 0))
        group2.add_child(sphere)
        point = sphere.world_to_obj(Point(-2, 0, -10))
        self.assertEqual(point, Point(0, 0, -1))


if __name__ == '__main__':
    main()

shapes.py

from matrices import Matrix, IDENTITY_MATRIX
from materials import Material


class Shape:
    def __init__(self, transform=None, material=None, parent=None):
        if transform is None:
            self.transform = IDENTITY_MATRIX
        else:
            self.transform = transform
        if material is None:
            self.material = Material()
        else:
            self.material = material
        self.parent = None

    def __repr__(self):
        return f'{self.__class__.__name__}({self.transform},{self.material})'

    def intersect(self, ray):
        raise NotImplementedError()

    def normal_at(self, point):
        raise NotImplementedError()

    def world_to_obj(self, point):
        if self.parent is not None:
            point = self.parent.world_to_obj(point)
        return self.transform.inverse() * point

入出力結果(Bash、cmd.exe(コマンドプロンプト)、Terminal、Jupyter(IPython))

C:\Users\...>py shapes_test.py
.....
----------------------------------------------------------------------
Ran 5 tests in 0.002s

OK

C:\Users\...>