Box2D libgdx多边形形状

Question

为什么这工作正常：

Vector2[] vertexArray = new Vector2[3];
vertexArray[0] = new Vector2(0f, 0f);
vertexArray[1] = new Vector2(1f, 1f);
vertexArray[2] = new Vector2(2f, 5f);

polygonShape.set(vertexArray);

这会产生运行时错误

Vector2[] vertexArray = new Vector2[3];
vertexArray[0] = new Vector2(0f, 0f);
vertexArray[1] = new Vector2(1f, 1f);
vertexArray[2] = new Vector2(2f, 2f);

polygonShape.set(vertexArray);

错误：

AL lib: (EE) alc_cleanup: 1 device not closed
Assertion failed!

Program: C:\Program Files\Java\jre1.8.0_25\bin\javaw.exe
File: /var/lib/jenkins/workspace/libgdx/extensions/gdx-box2d/gdx-box2d/jni/Box2D/Collision/Shapes/b2PolygonShape.cpp, Line 223

Expression: false

这没有任何意义。第一个代码工作正常，三角形画好了，但第二个代码不行。有人能解释一下我做错了什么吗...

Answer 1

顶点（0,0）、（1,1）、（2,2）都在一条直线上-它们不构成多边形。这导致触发断言，如错误消息（b2PolygonShape.cpp，第223行）所示