Data flow today!  
How to get information from your program into the graphics card!
	CPU program to shaders
	Vertex shader to Fragment shader
	Can't go from vertex shader to vertex shader
	Or fragment shader to fragment shader
	No sideways data movements!
	Vertex shaders go first, then fragment
	You can't control the order of vertex shaders
		Or fragment shaders
	Fine for 3D, hard for general purpose
		Computer shaders are also governed by rules

First:  Data Types in GLSL
	float
	int
	bool
	It does have double, in OpenGL 4.0+
		Didn't before that
		Graphics cards are bad at 64-bit floating point
		AMD was ahead here least I looked
	No implicit conversion from float to int or int to float
	No requirement for particular bit sizes (up to the GPU manufacturer)
		But, int is at least 16
	No bitwise operations
	vec2 (and 3 and 4), and ivec, and bvec
	Vectors have members x, y, z and w
	Also r, g, b, and a
	Also s, t, p, and q (for texture coordinates)
	"swizzling"
	Can also use array notation
	mat2, mat3, and mat4
		Column-major
		Can treat it as an array of columns which are vectors
		Double-index works
	samplers:  Won't make sense until we talk about textures
	struct and arrays work
	Constructor notation, NOT C static casts

Qualifiers:
	const:  Like in C
	attribute:  Frequently changing, from application to vertex shader
		Can't modify these in the shader
	uniform:  Infrequently changing, from application to either type of shader
		Can't modify these in the shader either
	varying:  Information passed from a vertex shader to a fragment shader
		This is obsolete, but you might see these in older tutorials
			Replaced with in/out declarations
			Easy to update older shaders
		Vertex shader writes these, per vertex
		Fragment shader can read them, interpolated between vertices
		Fragment shader can't write these
	attribute, uniform, and varying have global scope in the shader

Without a qualifier:  "normal"
	Global scope is shared between shaders of a type (vertex or fragment)

Other stuff:
	No goto or switch
	Calling:  in, out, inout, but NOT by reference (copy at beginning and/or end)
	swizzling and vector components

It's kind of a hassle to have the programs embedded in the C code.
	Loading from a file (we already did)
	We can change them without recompiling the program!
	Could have put it in a string

Lab today:  Make a Christmas Tree with Instanced Rendering!
	Don't add any more vertices for this, unless you want to make it non-flat
		25% EC bonus on the assignment if you do make the tree non-flat
		Do the assignment normal first
	Make at least 10 layers
	I'll draw a picture of what I'm hoping for on the board
	Don't have to decorate the tree