Blender - Blender is the open source, cross platform suite of tools for 3D creation.
VCV Rack - A cross-platform modular synthesizer.
Structure Synth - Structure Synth is a tool for creating 3D structures from a set of user specified rules.
Pure Data - Pd (aka Pure Data) is a real-time graphical programming environment for audio, video, and graphical...
Mandelbulber - A 3D fractal renderer.
miRack - Eurorack-style modular synthesizer for iOS.