Let's switch to a C++ demo
	I actually wrote one a couple years ago
	We took a function out of it, but I forgot I'd finished so much of it
	Did add a program that makes functions

Geometry shaders!
	The most flexible type in the pipeline
	Consequently the easiest area to make a good hangup
	But, they also have great power to change things!

The pipeline:  https://www.khronos.org/opengl/wiki/Rendering_Pipeline_Overview

Let's copy something with a geometry shader!
What geometry shaders do:
	Input:  Primitives, POST vertex shader!
	Output:  Primitives, not to be vertex shaded!
		Remember the order here, since it makes a fair bit of difference

Ok, copying the triangle:
	input, and layouts (lines)
		Comes as an array
	output, and layout again
		EmitVertex() sort of takes care of the array thing
		No GL_LINES here, but we can use line_strip and EndPrimitive()
		Copying over of colors:  Can make a difference
			Suggested reference:  https://www.khronos.org/opengl/wiki/Geometry_Shader
			Another suggestion:  http://www.lighthouse3d.com/tutorials/glsl-tutorial/geometry-shader/

Exploiting Parallelism:  Invocations
	We can make the duplicate using another invocation, with gl_InvocationID
	Only on OpenGL 4.0+
	Can't run it in a loop, or recursively, or anything like that
		Can have a loop inside it if you want
		Feedback, which we haven't got to yet, can sort of give you this

Can access uniform variables in the geometry shader
	So we could kinda just not use the vertex shader...
	But we have less invocations to work with
	And we have to have a vertex shader program anyway
	Certainly can, though!
	We could cull vertices above a certain point that way...

Another use:  Normal Vectors
	Since we've got all three points of a triangle, we can calculate a face normal
	Important for lighting
	Which direction should it go?
		Usually depends which order the points are specified 
		Clockwise vs. counterclockwise
		OpenGL defaults to counter-clockwise, but you can change it
		Should we calculate some?  It's just a cross product
		I'd like to do it Monday at the latest