geometry > 中心からの線と交わるstar shape(星形)のedgeを探す > find_rayCrossing_starShapedEged_180417 v0.2

```txt:動作環境
GeForce GTX 1070 (8GB)
ASRock Z170M Pro4S [Intel Z170chipset]
Ubuntu 16.04.4 LTS desktop amd64
TensorFlow v1.7.0
cuDNN v5.1 for Linux
CUDA v8.0
Python 3.5.2
IPython 6.0.0 -- An enhanced Interactive Python.
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
GNU bash, version 4.3.48(1)-release (x86_64-pc-linux-gnu)
scipy v0.19.1
geopandas v0.3.0
MATLAB R2017b (Home Edition)
ADDA v.1.3b6
gnustep-gui-runtime v0.24.0-3.1
PyMieScatt v1.7.0
```

v0.1: [geometry > 中心からの線と交わるstar shape(星形)のedgeを探す > find_rayCrossing_starShapedEged_180417 v0.1](https://qiita.com/7of9/items/7ddef458743dc8351fa8)

### 処理概要

- 星形の中心からrayを飛ばす
- rayが交差する星形の辺を見つける

### v0.2

v0.1では頂点の組合せを元に辺を自動定義していた。
これでは星形と五角形の区別はできない。

星形と分かるように辺の情報を入力するようにした。

- geometry_lineintersect_180415.py v0.2を使用

```py:find_rayCrossing_starShapedEged_180417.ipynb
%matplotlib inline

import numpy as np
import matplotlib.pyplot as plt
from pylab import rcParams
from itertools import combinations
import geometry_starShaped_180428 as GSS
import geometry_lineintersect_180415 as GLI

'''
v0.2 Apr. 28, 2018
  - exclude vertices pairs not included in the output from [geometry_starShaped_180428]
  - import geometry_starShaped_180428
  - remove: import geometry_starShaped_180415
v0.1 Apr. 17, 2018
  - check the crossing
      + import [geometry_lineintersect_180415]
  - define the ray from the center
    + draw the ray
    + add [xs_ray], [ys_ray]
    + add [theta_deg]
  - add idxs_seq[], combs[]
  - import [combinations]
  - branched from [geometry_starShaped_180414.ipynb]
'''

rcParams['figure.figsize'] = 14, 7
rcParams['figure.dpi'] = 110

# 1. obtain star shaped points
RAD_INNER = 5
RAD_OUTER = 10
xs_str, ys_str, edgeidx = GSS.get_starShaped(RAD_INNER, RAD_OUTER)

# 2. obtain combinations of points
idxs_seq = range(len(xs_str))  # sequential indices to obtain combinations
combs = []  # combinations to obtain all the edges
for acomb in combinations(idxs_seq, 2):
    combs += [acomb]
print(combs)

# 3. define the ray from the center
theta_deg = 0.0  # [deg] 0 for rightward direction, 90 for downward direction
radius = RAD_OUTER * 1.1  # 1.1 to cross the outmost edge
xs_ray, ys_ray = [0.0], [0.0]  # center
xs_ray += [radius * np.cos(np.deg2rad(theta_deg))]  # outmost
ys_ray += [radius * np.sin(np.deg2rad(theta_deg))]  # outmost
print(xs_ray, ys_ray)

fig = plt.figure()

ax1 = fig.add_subplot(1, 2, 1)
ax1.scatter(xs_str, ys_str)
ax1.set_xlabel('x')
ax1.set_ylabel('y')
ax1.plot(xs_ray, ys_ray)
ax1.grid(True)

# 4. find crossing edges
a1 = np.array([xs_ray[0], ys_ray[0]])
a2 = np.array([xs_ray[1], ys_ray[1]])
for aidx in combs:
    #print(aidx, edgeidx)
    if list(aidx) not in edgeidx:
        continue
    b1 = np.array([xs_str[aidx[0]], ys_str[aidx[0]]])
    b2 = np.array([xs_str[aidx[1]], ys_str[aidx[1]]])
    res = GLI.is_intersected(a1, a2, b1, b2)
    if res:
        xs_draw = [b1[0], b2[0]]
        ys_draw = [b1[1], b2[1]]
        ax1.plot(xs_draw, ys_draw)


fig.tight_layout()

```

![qiita.png](https://qiita-image-store.s3.amazonaws.com/0/32870/3810ef57-72a1-bbea-e8c3-51091952d273.png)


[v0.1](https://qiita.com/7of9/items/7ddef458743dc8351fa8)の時と比べて希望外の辺は除外された。

一方で、rayが交差していない辺も見られている。辺が無限長さになった時に交差するという定義になっているのが理由だろう。