Shader

A programmable function executed in parallel on the GPU: shaders define all modern 3D graphics, from geometry manipulation to final pixel color.

Shaders are small, highly parallel programs central to the graphics pipeline. They execute directly on the Graphics Processing Unit (GPU), allowing for massive parallel computation across thousands of cores. The two core types are the Vertex Shader, which transforms 3D model coordinates (vertices) into 2D screen positions, and the Fragment Shader (or Pixel Shader), which calculates the final color, lighting, and texture for each pixel on screen. This architecture enables complex, real-time effects like dynamic shadows, realistic reflections, and post-processing filters. Developers write these programs using specialized languages like GLSL (OpenGL Shading Language) or HLSL (High-Level Shading Language) to dictate precisely how a 3D scene is rendered.

https://www.vulkan.org/