Motivation

I have a lot of pictures hanging on the walls in my house and spotlights to illuminate them. The spotlights emit a fairly broad beam and also illuminate much of the surrounding wall, ceiling and sofa.

I wanted to improve the contrast and look of the pictures and reduce light going to the surrounding.

Principle

The idea is to calculate a lamp shade geometry that would cut off light at the edges of a picture given the geometry and relationship between the spotlight and the picture frame.

You will need:

1. size of the picture in mm (width, height)
2. distance of the spotlight center from the wall
3. distance of the spotlight center from the top of the picture frame
4. relative point where the center of the spotlight is pointing (center of the picture by default)

How to make it

You will need CadQuery to generate a custom shade for your picture and room. Download and install according to their instruction. (https://cadquery.readthedocs.io/en/latest/)

To make this easier to use I also recommend installing cq-editor.

Open the file lamp_shades_cq.py in cq-editor or any editor of your choice. Adjust the variables at the top of the file.

Once the file is executed with cadquery, it will output an STL file of the format pic_70x100.stl (for 70x100cm picture frame).

Update:

• added settings to adjust the top and bottom angles for a more rectangular beam (gamma_balance)
• added option to make the shade thinner towards the end to save material (flap_thick_end)

Update 2:

• made the base completely round and the transition directly from the round base to the square end for a much smoother appearance

Print settings

I am using AnkerMake to slice the file and had great success with PLA+ and PETG.

Material: PETG Nozzle: 260°C Bed: 80°C Infill: Gyroid, 20% Adhesion: Brim

No supports required!