# My Stars won't appear!

**URL:** <https://talk.code3dgames.com/t/my-stars-wont-appear/326>\
**Category:** Uncategorized\
**Created:** [July 21, 2021, 1:49pm UTC](https://talk.code3dgames.com/t/my-stars-wont-appear/326 "2021-07-21T13:49:27Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Martin](https://talk.code3dgames.com/user_avatar/talk.code3dgames.com/martin/32/41_2.png) [@Martin](https://talk.code3dgames.com/u/Martin)\
**Post date:** [July 21, 2021, 1:49pm UTC](https://talk.code3dgames.com/t/my-stars-wont-appear/326/1 "2021-07-21T13:49:28Z")

</div>

Yea my Stars wo’t appear…  
My Output say:  
Uncaught TypeError: Cannot read property ‘push’ of undefined  
at addBackground (VM59 code.html:171)  
at VM59 code.html:39  
at VM56 \_.html:10  
addBackground @ code.html:171  
And my Url is:  
[https://www.code3dgames.com/3de/#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](https://www.code3dgames.com/3de/#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)

---

<div class="post-metadata">

**Author:** ![chris](https://talk.code3dgames.com/user_avatar/talk.code3dgames.com/chris/32/5_2.png) [@chris](https://talk.code3dgames.com/u/chris)\
**Post date:** [July 21, 2021, 2:11pm UTC](https://talk.code3dgames.com/t/my-stars-wont-appear/326/2 "2021-07-21T14:11:08Z")

</div>

There is a small problem at the start of the `addBackground()` function. The `shape` and `cover` variables are mixed up:

```javascript
  var shape = new THREE.PointsMaterial({color: 'white', size: 2});
  var cover = new THREE.Geometry();

```

Shapes are always a kind of “geometry” and covers are always a kind of “material.” So, you can fix the error by switching the two variables:

```javascript
  var cover = new THREE.PointsMaterial({color: 'white', size: 2});
  var shape = new THREE.Geometry();

```

Also, at the bottom of the `addBackground()` function, the code currently tries to add the cover to the scene:

```javascript
  var stars = new THREE.Points(shape, cover);
  scene.add(cover);

```

You’ll need to change that to add the stars to the scene instead:

```javascript
  var stars = new THREE.Points(shape, cover);
  scene.add(stars);

```

There is one other small problem in the `addBackground()` function. Instead of `Math.PI` when computing the declination, the code currently has `Math.Pi` (lowercase `i`):

```javascript
    var ra = 2 * Math.PI * Math.random();
    var dec = 2 * Math.Pi * Math.random();

```

If you change that so it’s `Math.PI` like the right ascension, then the background code will work just fine:

```javascript
    var ra = 2 * Math.PI * Math.random();
    var dec = 2 * Math.PI * Math.random();

```

Let me know if you run into any other problems,

-Chris

---

<div class="post-metadata">

**Author:** ![Martin](https://talk.code3dgames.com/user_avatar/talk.code3dgames.com/martin/32/41_2.png) [@Martin](https://talk.code3dgames.com/u/Martin)\
**Post date:** [July 21, 2021, 4:08pm UTC](https://talk.code3dgames.com/t/my-stars-wont-appear/326/3 "2021-07-21T16:08:06Z")

</div>

Perfect! now everything is working fine!

---

<div class="post-metadata">

**Author:** ![383838](https://talk.code3dgames.com/user_avatar/talk.code3dgames.com/383838/32/45_2.png) [@383838](https://talk.code3dgames.com/u/383838)\
**Post date:** [November 8, 2021, 12:26pm UTC](https://talk.code3dgames.com/t/my-stars-wont-appear/326/4 "2021-11-08T12:26:20Z")

</div>

能不能发一下《倾斜板子游戏》的完整代码？

---

<div class="post-metadata">

**Author:** ![chris](https://talk.code3dgames.com/user_avatar/talk.code3dgames.com/chris/32/5_2.png) [@chris](https://talk.code3dgames.com/u/chris)\
**Post date:** [November 8, 2021, 12:30pm UTC](https://talk.code3dgames.com/t/my-stars-wont-appear/326/5 "2021-11-08T12:30:43Z")

</div>

本书的完整代码可在本书的主页上找到： [https://pragprog.com/titles/csjava2/3d-game-programming-for-kids-second-edition/](https://pragprog.com/titles/csjava2/3d-game-programming-for-kids-second-edition/).

完整代码的直接链接是：[https://media.pragprog.com/titles/csjava2/code/csjava2-code.zip](https://media.pragprog.com/titles/csjava2/code/csjava2-code.zip)