How TOPs Actually Work in Houdini (PDG) | Procedural Dependency Graph | Image Manipulation Tutorial

In this video I am going to show you how TOPs actually work and go through the official "Tutorial 2 Image Manipulation" from Houdini documentation, clarify a few things, and point out some challenges and issues with the original documentation and show you the solutions.

This is a very technical walkthrough and involves things like shell processing, python scripting and command line usage.

Contents
00:00 Welcome
=========== Basic Concepts ===========
00:50 What is PDG Really - A Batch Processing Framework
01:45 How Manually Command Line Processing Work
03:22 ImageMagick Command Line Usage
05:20 "Node Based Command Processing"
05:45 ImageMagick TOP Node
06:22 Configure ImageMagick Binary for ImageMagick TOP Node
07:19 Overview of Available TOP Node Operations
09:50 Understanding TOP Concepts
10:13 File Pattern TOP Node
11:45 The Two Kinds of Objects/Entities TOP Deal With
13:00 File Path Syntax Stuff
14:48 Inspect Nodes with Python (Python Shell) `hou` and `pdg`
15:00 `hou` Package API
16:38 `pdg` Package API
18:14 localVariables() and localAttributes() API
=========== The Actual Tutorial ===========
18:55 Tutorial Overview
20:04 Software Installation (ffmpeg and imagemagick)
20:10 imagemagick
20:22 ffmpeg
21:12 Example Image Archives
21:35 Tutorial Outputs
22:07 General Setup and Interface Layout Overview
22:42 Walkthrough: File Pattern (Split Files into Separate Items)
24:40 Understanding Work Items & "Work Streams"/Threads/Processes
26:35 Walkthrough: File Decompress
27:00 Single Process vs Many Processes
28:27 Tutorial Walkthrough: Step 1 - Convert Images with Image Magick & Two Challenges
29:54 Convert Many Image in A Single Work Item vs Converting A Single Image At A Time
33:30 Input Attributes (on ImageMagick)
51:44 File Compress TOP Node
35:30 How Everything Works, Really, In A Single Sentence
36:30 Troubleshooting Attribute Name Reference in File Path
40:11 Tutorial Walkthrough: Step 2 - Montage Generation from Image Sequence (still uses ImageMagick node)
=========== Additional Talk ===========
40:58 Recap
41:22 ☠️Part 3 of the Tutorial - How It Doesn't Work
41:56 Filter by Expression TOP Node
44:42 Debugging Python Expressions
46:42 Using `print()` to Debug Python Expressions
48:57 ❌Potential Bug of Filter by Expression Node???
51:38 Partition by Attribute TOP Node