Week 2 · Computer Aided Design

What I did in Week 2

The focus this week was on understanding the basics of 2D and 3D CAD, testing different software, and preparing media in efficient formats for documentation.

2D software: tried raster and vector tools for drawing and editing.
3D software: explored modeling tools and parametric workflows.
Compression: standardized image and video sizes and formats for the class site.
Final project concept: modeled ideas that could evolve into the final project.

Assignments for the week:

Model (raster, vector, 2D, 3D, render, animate, simulate, ...) a possible final project.
Compress images and videos, and post a description with design files on the class page.

Week 2 assignments and files

These are the pages and files associated with my Week 2 work.

Computer aided design notes

CAD in this context covers both 2D drawings and 3D volumes, each with different tools and workflows.

2D: raster and scan

Raster: images made of pixels, good for photos and detailed artwork.
Scan: converting hand drawings into a 2D digital representation.

2D tools

GIMP: open source image editing.
Photoshop: commercial image editing.
Krita / MyPaint: open source painting and drawing tools.
ImageMagick: command-line toolkit for coding image conversions and processing.

Larger images take more space and slow down loading, so compressed formats and resized media are important.

Image formats

JPG: compressed, good for documentation and web use.
PNG: uncompressed (or lossless), good as an “engineering” image format.
WEBP: an image format optimized for browsers.

PNG vs JPG: they can look perceptually similar, but PNG is better for technical images while JPG is better for lightweight visual documentation.

Image conversion and compression

On macOS, I can use the terminal and ImageMagick to batch convert and compress images for the site.

# convert PNG to JPG:
convert input.png output.jpg

# convert all PNGs to JPGs:
mogrify -format jpg *.png

# convert SVG to PNG at 1000 DPI:
convert -density 1000 -units PixelsPerInch input.svg output.png

# compress JPG to quality 50% width 1000:
convert input.jpg -quality 50% -resize 1000 output.jpg

# compress all JPGs to quality 50% width 1000:
mogrify -quality 50% -resize 1000 *.jpg

3D and parametric design

For 3D work, the key is to maintain the design history so changes remain manageable and parametric.

Vector and 3D tools

Mods: supports workflows to vector cutting machines.
FreeCAD: parametric modeling tool with libraries.
Blender: powerful 3D tool with CAD-related extensions and automation.
OpenSCAD: script-based modeling using code.
Kokopelli / Kokompe: tools that can use serial input for design.
GrabCAD: a platform to share and download 3D models.

Parametric ideas

Parametric design is a key concept: you define parameters so that changing one value updates the whole model.

In a parametric kit, a single slot size parameter defines all joints, making it easier to adapt to different materials and kerf.

2D to 3D transitions

Span, loft, and sweep profiles to generate surfaces.
CSG (constructive solid geometry) to combine and subtract primitives.

Interchange formats

STL: common format for sharing raw 3D geometry.
FreeCAD libraries for reusable parametric components.

Applications and engines

Game engines: Unity and similar tools for interactive 3D environments.
VR/AR: immersive 3D environments for visualization.
Physics engines: simulate motion, collisions, and animation so they do not need to be keyframed manually.

Audio and video notes

I also reviewed tools and workflows for audio and video editing, and how to encode clips for web documentation.

Editing tools

Audacity: open source audio editor.
Kdenlive: open source video editor.
ffmpeg: command-line tool for converting and processing video and audio.

ffmpeg examples

# variable bit rate 1080p MP4:
ffmpeg -i input_video -vcodec libx264 -crf 25 -preset medium -vf scale=-2:1080 -acodec libmp3lame -q:a 4 -ar 48000 -ac 2 output_video.mp4

# fixed bit rate 1080p:
ffmpeg -i input_video -vcodec libx264 -b:v 1000k -vf scale=-2:1080 -acodec mp2 -b:a 256k -ar 48000 -ac 2 output_video.mp4

# no audio:
ffmpeg -i input_video -vcodec libx264 -b:v 1000k -vf scale=-2:1080 -an output_video.mp4

# crop size (width:height:xoffset:yoffset):
ffmpeg -i input_video -vf crop=1500:800:200:100 -vcodec libx264 -b:v 1000k -an output_video.mp4

# trim time (-ss start time, -t duration):
ffmpeg -i input_video -vcodec libx264 -b:v 1000k -an -ss 00:00:10 -t 00:00:10 output_video.mp4

# mix audio and video:
ffmpeg -i input_video -vcodec libx264 -b:v 1000k -vf crop=1120:876:0:100 -i input_audio -acodec mp2 -b:a 256k -ar 48000 -ac 2 -ss 00:00:20 -t 00:00:20 output_video.mp4

# crop, pan, composite:
ffmpeg -i input_video_1 -i input_video_2 -filter_complex \
"[1:v]crop=175:95:930:860[cropout];[cropout]scale=350:190[scaleout];\
[0:v][scaleout]overlay=10:10[outv]" -map "[outv]" -vcodec libx264 -b:v 1000k \
-map 0:a -acodec mp2 -b:a 256k -ac 2 -t 00:00:05 output_video.mp4

# numbered images to video:
ffmpeg -r 30 -i %04d.jpg -vcodec libx264 -b:v 1000k -vf scale=-2:1080 -an output_video.mp4

AI tools: There are emerging AI systems for 2D and 3D generation, but they require attention to copyright and licensing.

Evidence (images)

Replace these placeholder images in images/week2/ with screenshots that document my Week 2 CAD work.

2D software trying

Raster and vector tests for drawings and exports.

Image and video compression

Before and after results with ImageMagick and ffmpeg.

3D software trying

Testing FreeCAD, Blender, and parametric workflows.

Sketchfab uploads

Publishing 3D models for online viewing.

Next step

With a basic CAD toolkit and media workflow in place, the next weeks will connect these tools to digital fabrication processes and more detailed project development.