1. ATEC 4371.001 Procedural Animation Introduction to Procedural Methods in 3D Computer Animation Dr. Midori Kitagawa

2. In class  Pay attention  Take notes  Learn  Be ready for a pop quiz

3. Lecture 3: Houdini foundations  Custom desktops  Connection between nodes  Houdini contexts  Three functions of a node connection  Particle systems

4. Custom desktops  You can move your custom desktops to another machine by copying.desk fines in houdini13.0/desktop

5. Connection between nodes  Function of a connection between nodes differs depending on which context it is in.

6. Houdini contexts Major parts of Houdini (contexts) and corresponding node networks:  /chCHOP (channel operators) network  /imgCOP (composite operators) network  /objObjects, cameras, and lights  /obj/geoSOP (surface operators) network  /outROP (render outputs)  /partPOP (particle operators) network  /shopSHOP (shader operators) network  /vexVOP (VEX operators) network

7. Three functions of a node connection 1. Parenting (/obj only) 2. Passing data 3. Listing operations

8. 1. Parenting  Connection works as parenting. The transformations applied to a parent node are applied to its child nodes.  Only in /obj – the scene (object) level

9. 2. Passing date  Data are generated, modified and/or passed from an upper node to a lower node through the connection between the nodes.  In /obj/geo - the geometry (SOP) level and in other contexts

10. 3. Listing operations  Connections are used to list operations that are applied to the nodes.  Orders are often important but not always.  A later node can affect earlier node, e.g., POP network  In /out – ROP rendering outputs and in other contexts

11. Particle systems  Technique for modeling and animating a class of fuzzy objects, such as fire, clouds, and water.  Particle systems model such objects as clouds of primitive particles that define their volumes.  Over a period of time, particles are: generated into the system moved and changed within the system removed from the system

12. Particle systems  For each frame the system checks the current state of each particle and updates it for the current frame.  The state at the new frame depends on what happened in the past.  Can update itself properly only in a forward direction.  State dependent