Introduction

Computer Aided Design forms an important part in digital design and digital fabrication. My history with computer aided design began in 1994 with 3d Studio R1 for DOS. Later I learned about Rhinoceros and 3dsMax, worked with AutoCad during college and finally settled on a workflow combining the features of Blender, Rhinoceros and OpenSCAD for modelling. Some parts of computer aided design I hardly touch:

• Visual parametric modelling
• Materials and mapping
• Animation and simulation
• Rendering and compositing

For each of these I will have to learn something new.

Result

Because the text below will be quite long, it’s probably best to first show what this week’s work has lead to.

If the video doesn’t work: watch on youtube.

Think

Visual parametric modelling

I will use FreeCAD to draw an initial sketch of my final product.

Materials and mapping

By importing the FreeCAD model to blender I hope to assign fitting materials and textures to my object

Animation and simulation

Blender will also be used to animate and possibly simulate parts of the model. Animation would be particularly useful to show how I might make force sensitive buttons that still can be back-lit.

Rendering and compositing

Because my design will feature back-lit buttons, I will add realistic lighting to my final renders.

Make

Rhinoceros

Rhinoceros3d is familiar terrain form me. It allows for very fast previews of final products. Unfortunately, its destructive modelling workflow makes it cumbersome to iterate on previously constructed models. If measurements need to be altered once the model is made, parts of the geometry have to be deleted and rebuilt. For a first visualization, the free-form modelling workflow is great, so that’s what I used.

Base shape constructed from two circles and tangent lines	Used the trim command to delete lines

Base shape duplicated and offset to indicate height	Used the loft command to create the 3d shape of the base

A single key was made using two circles, connected by 2 lines	_ExtrudeCrv command used to extrude to a solid

Key shape duplicated 24 times with ArrayPolar command	3d keys

Used a boolean to cut keys from the top plate	Gave the top-plate a wood texture, for now

The final render from within Rhino gives a nice impression of what the end-result could be

FreeCAD

To start a part in FreeCAD, one has to select the option “part design” in the combobox at the to of the screen. The first part I want to make is the circular keyboard.

To make the design parametric, I will start a spreadsheet.

The keyboard will consist of buttons that describe 1/24th of a ring.

Two circles where made and two lines were drawn from the center to the edge of the outer circle.A horizontal construction line was made to keep the two outer edges of the button fixed in the horizontal center

By trimming, a 2d sketch of the key was constructed…	… and turned 3d by making a pad

Using the PolarPattern command the key was copied in a circular pattern to make up the keyboard

The key shape could be deformed and follow-up calculations weren’t executed correctly.

The second mistake was to confuse PolarPattern with PolarArray. PolarPattern joins copied geometry into one single mesh. I deeded PolarArray from the draft menu.

Now I was able to draw the key and it stayed fully constrained.

Spacing between keys

To parametrically have spaces between the keys I had to calculate the angle between keys based on the desired spacing.

x: the desired spacing between keys, r1: the inner radius, alpha: the desired angle

which led to the equation:

\[ \alpha=\arcsin{x \over r_1}\]

to calculate the angle of the spacing.

Entered the formulas into the spreadsheet

Adjusting the spacing in my spreadsheet directly changes this in the sketch, therefore changing it in the 3d object. The main keyboard is now fully parametric.

Top panel

The top panel of the instrument will be a flat, milky-white (opal) acrylic plate. For now the plate is designed only with the keys cut, using the keyboard part, previously described. The sketch for the top-panel:

Top panel sketch	Top panel

The command Cut command from the part workbench was used to make cut out the keys from the panel.

I decided to return to FreeCad at a later stage of the project because I really wanted to try rendering an animation in Blender.

Blender

Rhino is great for creating accurate but organic like models. It has a nice renderer but to generate a realistic image, Blender with it’s Cycles renderer would be a much better choice. Blender allows has some nice features I wanted to use and learn more about:

• creating a material that would simulate backlit opal acrylic
• lighting the object realistically
• animating the LED’s
• animating from different angles
• simulating the OLED display
• making clear LEDs and OLED are light emitting using a glow filter

Backlit RGB test

The final keyboard will partially communicate its state using RGB LEDs that are lighting an opal acrylic plate from the back. To visualize how that might look, an experiment was conducted in Blender, using the Cycles rendering engine and the Sub Surface Scattering material property.

A grid of thin, scaled cubes was constructed to act as walls that keep light from bleeding	The grid was set to have a high value for sub-surface scattering

A sphere with an emission material was used to simulate an RGB LED	The sphere was set to follow a circular path

The camera was animated to show the underside and the top-side of the geometry

The final render was set to denoise the images using hardware desnoising using the compositor

If the video doesn’t work: watch on youtube

Exporting from Rhino Importing in Blender

I chose to export the model as an .obj object, because it would let me integrate the textures and keep texture mapping. First I tried to export it as a NURBS object but blender didn’t like it.

I selected to export the object as a mesh	Rhino allows you to determine the mesh detail generated from the NURBS objects

Blender assumes that one unit is one meter, while most CAD software will assume that one unit is one millimeter. This always leads to having huge objects in Blender.

The imported objects are so large they fall outside of the z-buffer range and disappear	Scaling the object brings it back in visible range

Furthermore, Rhino exports all the loose parts of an object as one single object.

Blender has an option to separate all meshes

When separating meshes in loose parts, some surfaces may become separated.

Objects can be reconstructed from their loose parts using the weld modifier and applying it.

The final scene graph looked like this

Realistic lighting and materials

Two tricks were used to simulate realistic lighting

Using a HDRI image to light the scene	As an HDRI lightmap I chose an image of an indoor, industrial looking storage facility.

The added benefit was that this would also serve as the background of the animation.

For extra lighting I added two light planes, which also reflect on the wood surface

To create a glossy, slightly bumpy wood material I used the shader graph

The wood shader-graph	The final material, reflecting the light planes

Animating LED’s

Using the results of the backlight experiment I made the LEDs from spheres with a highly emissive material.

I made two sets of LED’s to simulate two chords being played

The two sets of LEDs were interfering with each other so I had to hide and show them in during the animation by setting animation keys for object visibility

The resulting timeline for the LEDs looks like this, changing the emission value and the visibility of the LEDs over time

Audio synchronisation

To show the LED’s reacting to the audio, four chords were extracted from the original youtube video.

OBS studio was used to rip the audio track from the youtube video. Audacity was used to extract four chord pairs .wav file was loaded into blender

Animating camera-angles

The animation sequence would show a couple of chord progressions being played on the device. Each different progression would show another camera angle, slowly panning before making a jump cut to the next angle.

To have more control over the camera a Track To constraint was added to the camera object, making it point towards another object as the target.

A single camera was used to simulate multiple shots by making the camera jump from one position to another and then track slowly to another position.

Bezier path interpolation make the camera motion look more naturally

But I didn’t like that so I made all movements linear, which gave a more controlled feel

Animate the OLED display

The OLED display had to change text once in a while.

I found a nice font for the OLED display.

Using the GIMP I made a couple of diplay states in one file, as separate layers

First as separate text objects…	…and then merged to have 10 text states

Storing all LED states to one separate numbered files allowed me to have an image sequence as a shader

An image sequence texture can point to any numbered image file

But to have the texture change for a determined amount of frames proved challenging and I had to make a “driver”, linking multiple variables together

Post processing glow

When everything was moving the way I wanted it to I wanted something to make clear that the LEDs and the OLED were actually light sources. This was achieved by adding a glow in the compositor.

Linking the denoised image to the glow filter allows you to add glow to specific parts of the image

Movie and audio

Rendering 900 frames of animation resulted in 900 separate images. Using ffmpeg I could easily convert those images into an mp4 file

ffmpeg -r 24 -i %04d.png -vcodec libx264 -b:v 768k -vf scale=-2:720 -an instrument_previz.mp4

And lastly, I had to add the audio to the final animation. This didn’t succeed at first because the animation was rendered at a different framerate as ffmpeg was set to, but in the end it matched up nicely.

I used KDENLive to add the sound to the final animation

2D Vector drawing

A lot of 2d vector drawing software exists. The most familiar open source solution is InkScape. I am not fond of InkScape, as it is very slow on most systems, due to the lack of GPU support. Most 3d software have powerful 2d drawing capabilities and of the 3d packages I know it is my opinion that Rhino3D has one of the most capable 2d drawing capabilities. It has freeform capabilities that rival 2d drawing software but with tools that are often found in classic CAD software packages. I once bought Rhino3D because of it’s excellent 2d capabilities.

Kicad footprints

To show my proficiency in drawing 2d vector images, I decided to dust of an old project I created 13 years ago, but never published before. It is a set of KiCAD footprints that are essentially a set of coins, drawn at 1:1 scale, that can be loaded into any PCB design as a size reference. For this I needed vector drawings of coins. I tried to get these by converting bitmaps to vector drawings but the results weren’t good enough, so I proceeded to draw them by hand.

Rhino3D had good options for loading in background bitmaps to act as a reference. I traced all common US and EU coins using NURBS splines, circles and the trim operation.

In the KiCAD footprint editor there is an option to load .dxf files	This results in a clean footprint to be used in a project.

Most common US and EU coins are represented

The resulting footprint library can be found here.

Check

Did I achieve my goals for this week?

Visual parametric modelling

I will use FreeCAD to draw an initial sketch of my final product.

It took me some time to get used to the parametric modelling mindset. I am confident now I will be able to model the rest of the device in FreeCAD but I wasn’t able to do the entire design using this workflow. Ultimately I resorted to my old tricks to proceed animating and lighting. This goal is half reached but will be a big part in future work.

Materials and mapping

By importing the FreeCAD model to blender I hope to assign fitting materials and texturemaps to my object

Which turned out to be the Rhino model, but nevertheless I think I was able to nicely visualize a glossy, blinky instrument.

Animation and simulation

Blender will also be used to animate and possibly simulate parts of the model. Animation would be particularily useful to show how I might make force sensitive buttons that still can be back-lit.

Although simulation hasn’t been part of the animation, I’m still happy how it turned out. The final animation quit glossy and glowy and gives a sort of tranquil feeling to the user. Due to the slow camera movements but probably als due to the isolated chords being played. It conveys nicely how the instrument should look but I’m not convinced this animation shows the entire purpose of the device. For that you still need my explanation.

Rendering and compositing

Because my design will feature back-lit buttons, I will add realistic lighting to my final renders.

It’s glowy!

Reflect

I set out to do parametric modelling but really liked having a chance to do some animation and visualization. I am happy with the end result but putting more time into modelling would probably have helped me out better in the course of the project.

Files

• Rhino Project
• Blender Project (without textures))
• FreeCAD Keyboard
• OLED Display texture
• Coin size reference footprints
• Coin size reference original files