GLSL (OpenGL Shading Language) is a high-level shading language designed for the OpenGL API. It empowers developers to directly program the GPU for real-time rendering, dictating how pixels appear and vertices transform on screen. GLSL is crucial for achieving modern visual effects, from complex lighting and shadows to post-processing effects and realistic material rendering.
Shader Types
GLSL programs are typically composed of different types of shaders, each performing a specific task within the rendering pipeline:
- Vertex Shader: Processes individual vertices. It can modify vertex positions, normals, and texture coordinates, transforming 3D models into 2D coordinates on the screen.
- Fragment Shader: Processes individual "fragments" (potential pixels). It determines the final color, depth, and other properties of a pixel based on interpolated data from the vertex shader, textures, and uniform variables. This is where lighting calculations, texture mapping, and color blending often occur.
Other shader types include Geometry Shaders, Tessellation Shaders (Control and Evaluation), and Compute Shaders, which offer further control over geometry generation and general-purpose GPU computing.
Here's a small example of a GLSL Fragment Shader that outputs a red color:
#version 330 core // Specify the GLSL version
out vec4 FragColor; // The output color for the fragment
void main()
{
// Assign a red color (RGBA: Red, Green, Blue, Alpha)
// Values range from 0.0 to 1.0
FragColor = vec4(1.0f, 0.0f, 0.0f, 1.0f);
}
GLSL shaders are written as plain text files, then compiled at runtime by the OpenGL driver and linked together to form a shader program that runs on the GPU.
