Calculates number of indices needs to be passed to an OpenGL VBO object

calcNumIndices.h

// Calculates number of indices needs to be passed to a VBO object.
// Formula's from: https://www.opengl.org/sdk/docs/man2/xhtml/glBegin.xml
// primitive_type can be GL_POINTS, GL_LINES, etc.
unsigned calcNumIndices(unsigned numVertices, GLenum primitive_type)
{
	unsigned numIndices = 0;
	switch (primitive_type)
	{
	case GL_LINE_LOOP:
	case GL_POINTS:
		numIndices = numVertices;
		break;
	case GL_LINES:
		numIndices = numVertices * numVertices;
		break;
	case GL_LINE_STRIP:
		numIndices = numVertices - 1;
		break;
	case GL_TRIANGLES:
		numIndices = numVertices * numVertices * numVertices;
		break;
	case GL_QUADS:
		numIndices = numVertices * numVertices * numVertices * numVertices;
		break;
	case GL_QUAD_STRIP:
		numIndices = numVertices * numVertices - 1;
		break;
	case GL_TRIANGLE_STRIP:
	case GL_TRIANGLE_FAN:
		numIndices = numVertices - 2;
		break;
	default:
		break;
	}
	return numIndices;
}