Apps to Drawing 2D

SolveSpace is a free and open-source 2D and 3D CAD program with a focus on parametric modeling and constraint solving. It is known for its portability, ease of use, and clear workflow, making it suitable for various engineering and design tasks, including product design and preparing models for 3D printing.

LibGDX is a robust, free, and open-source Java game development framework designed for creating 2D and 3D games across multiple platforms including Windows, macOS, Linux, Android, and web browsers.

Gimp Painter is a discontinued fork of GIMP specifically enhanced with tools for digital painting and drawing. It aimed to provide artists with advanced brush capabilities and performance optimizations tailored for creative workflows on the GIMP platform.

Simple DirectMedia Layer (SDL) is a cross-platform, open-source development library offering low-level access to essential hardware like audio, input devices, and graphics APIs (OpenGL, Direct3D). It's a fundamental layer for game development and creating interactive applications.

Vulkan is a modern, low-overhead, cross-platform graphics and compute API that provides developers with explicit control over GPU hardware for optimal performance in demanding 3D applications, gaming, and simulations.

BRL-CAD is a powerful open-source solid modeling system utilizing Constructive Solid Geometry (CSG). It provides a comprehensive suite for design, analysis, and visualization, suitable for a range of engineering and scientific applications.