Voppity Dop Sop Chop

These are some notes I have taken while watching some beginner Houdini videos, primarily discussing the language of Houdini.
NOTE: Keep in mind that this is pretty messy and information is a bit all over the place. I am basically treating this post as a way of taking notes while learning new things on Houdini basics from the SideFX site.

Nodes/Operators

Surface Operators (SOPS) : 

  Deals with geometry.

  Geometry, volumes, attributes, VFX.

    e.g.

Procedural Soccer Ball - Network

Model created from network to the right.

Channel Operators (CHOPS):

  Deals with motion.
  Procedural motion FX (this can be used in place of keyframes for a more realistic motion), e.g.

Add motion FX to the Y axis

alter the way that the motion behaves

kinematic solvers, timing, sound, constraints

Dynamic Operators (DOPS):

  Deals with simulation.
  Solvers, forces and collisions.
  e.g. Fluids, rigid bodies, particles, hair, fur, etc.

For example using the RBD Instanced Objects tool, I told the soccer ball to go to the corners of another cube. Then by putting a ground plane down, you get this simulation:

You can alter different aspects of the simulation in the AutoDopNetwork, something that is automatically created when you create a simulation.

Vex Operators (VOPS):

  Deals with shader building.
  Shader building, geometry, compositing, VFX.
  "VEX" is actually a scripting language, a vector expression language.
  Entagma has a good resource for learning this HERE.
  These days a lot of people are doing this kind of work inside a "Wrangle Node", inside which you      can write VEX script.
 

example VEX script inside a wrangle node

Compositing Operators (COPS):

  Deals with Images.
  Houdini has it's own compositor.
  Comps, colour, masks, effects.

Render Operators (ROPS):

  Deals with outputs.
  Mantra nodes for rendering to Mantra, 3rd party renders, HQUEUE.
  Geometry, channels, comps, etc.

  You can have different renders within in the same scene doing different objects.
  These can feed in to a merge node at the bottom.
  You can have two different renders (say a RenderMan render and a Mantra render), that are then fed    into a compositing node which resolves everything at the end.

Parameters, Channels, and Attributes

Parameters

  Parameters are the options of a node.

parameters of a geometry node

  

Channels

  Channels is any parameter that has been keyframed. Once it has been keyframed, it qualifies as a        channel.

Attributes

  Attributes are things that we can assign to point to different places. They are named values used to      hold information.

  For example a geometry node has attributes such vertices, points, primitives, and objects. Point          color, position, UV coordinates, and normal, are stored as point attributes.