用C ++绘制矩形的函数

Question

I try to write a function that generates a rectangle which takes as input the following information:

topLeftPoint , and (width and height) of the desired rectangle. As the result it should return the coresponding vertices. I'm using the OpenGL coordinate system.

topLeftPoint can be a simple struct of two ints or Vec2 .

Here is an example of how I try to solve this task: example

 float verticesOfRectangle[] =   
{  
   in.x(), in.y(),  
   in.x(), in.y() - h,  
   in.x() + w, in.y()-h,  
   in.x() + w, in.y(),  
}

What is wrong with my code? My final shapes doesn't look like a rectangle. It looks more likes this: final shape

Answer 1

Guessing, reorder them like this:

float verticesOfRectangle[] =   
{  
   in.x(), in.y() - h,  
   in.x() + w, in.y() - h,  
   in.x(), in.y(),  
   in.x() + w, in.y(),  
}

Answer 2

This should help you:

void glRecti(GLint x1, GLint y1, GLint x1+w, GLint y1-h);

The vertices are the two diagonal endpoints of the rectangle. (x1,y1) is the left topmost point while (x1+w, y1-h) is the right bottom most point, with w as the width and h as the height of the rectangle