OpenGL中投影变换函数的实现

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/zhouxuguang236/article/details/45012209

在某些情况下，我们需要自己实现透视投影和正射投影的函数，那么根据前一篇转载的博客，OpenGL投影矩阵的推导，我们很容易写出glFrustum和glOrtho函数的实现。

glFrustum的函数实现如下：

void MyFrustum (GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble zNear, GLdouble zFar)
{
	GLdouble matProj[16];
	memset(matProj,0,sizeof(GLdouble)*16);

	matProj[0] = 2*zNear/(right-left);
	matProj[2] = (right+left)/(right-left);

	matProj[5] = 2*zNear/(top-bottom);
	matProj[6] = (top+bottom)/(top-bottom);

	matProj[10] = -(zFar+zNear)/(zFar-zNear);
	matProj[11] = -2*zNear*zFar/(zFar-zNear);

	matProj[14] = -1;
	glMultTransposeMatrixd(matProj);
}

glOrtho函数实现如下：

void MyOrtho (GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble zNear, GLdouble zFar)
{
	GLdouble matProj[16];
	memset(matProj,0,sizeof(double)*16);

	matProj[0] = 2/(right-left);
	matProj[3] = -(right+left)/(right-left);

	matProj[5] = 2/(top-bottom);
	matProj[7] = -(top+bottom)/(top-bottom);

	matProj[10] = -2/(zFar-zNear);
	matProj[11] = -(zFar+zNear)/(zFar-zNear);

	matProj[15] = 1;
	glMultTransposeMatrixd(matProj);
}

希望对大家有用