Hardware and Software

• The Section
  • Pre 1992 there were mostly proprietary graphics standards
    • Each company had a graphics library.
    • And some languages had graphics facilities.
    • There was even PHIGS a standardized package.
• In 1992 OpenGL was released.
  • The descendants of this software have become the open standard for graphics work.
  • Direct3D on windows and Metal on Mac are proprietary competitors.
• A bit of history
  • The first computers had CPU driven graphics.
  • IE To draw a set of lines, the CPU
    • would loop through the array
    • Generate the graphics call to draw the lines
    • Send these to the graphics subsystem.
  • In most cases, it was probably the case that the CPU handled the graphics subsystem too.
  • The GPU was not a GPU but a fancy frame buffer.
    • Which quite possibly shared memory with the CPU.
  • This was exceedingly slow.
  • The big change was the GPU
    • Graphics Processing Unit.
  • This is called immediate mode.
    • Note, that this is mostly what we are doing in JavaScript.
• Notice a few things
  • Moving data across a bus, even if it is an internal bus is slow.
  • The CPU could be thought of as a "do everything" machine
  • But most graphics, in the end need a "do special things" machine.
    • These special things are simple, so we don't need a full CPU
    • And we tend to do these special things in batches of two to four.
    • But we loop over these things a lot of times.
  • Flynn's Taxonomy
    • SISD: Traditional Computing
    • 
    • MIMD: Committee Work
    • 
    • SIMD: Army
    • 
    • MISD does not make sense.
  • These are sometimes modified to SPMD, MPMD in the parallel world.
• Think about what you know about processing:
  • We take in 1,000 triangles.
  • We do the same thing to all of them.
  • We repeat this at the rasterization level
• Modern GPUs are a SPMD or SIMD's programmers ideal platform.
  • Versions of the graphics API's including OpenGL have moved towards this.
• The process has changed greatly
  • GPU's are now programmable.
  • The first part of most modern API's is to send the programs used to render the graphics scene.
  • Then send all of the data.
  • The commands to draw are usually very small.
  • Thus very little time is spent in the CPU performing graphics action.
• The programs are called shaders
  • The vertex shader works on primitives (triangles, lines, points)
  • The fragment shader works on the "pixels", but not really, the fragments really, but ...
  • OpenGL has other shaders as well but we will not mess with these.
  • Shaders are written in a language called GLSL (OpenGL Shading Language).
• There are differences between OpenGL and WebGL, but we will discuss these as we go along.
• Vulkan is the next step in the evolution of graphics.
  • This is a very low level language for graphics cards.
  • It fixes some problems in OpenGL
  • And adds more performance and functionality.
• So what
  • The book is going to use the old version of OpenGL for 2d.
  • I am going to use the html canvas for this.
  • We will then merge when we get to 3d.
  • In general
    • I don't know Vulkan, but I could learn it.
    • It is reasonably new and somewhat in flux
    • OpenGL has been written on top of it.
    • There is general agreement that it is probably not the API for a first level graphics course.