GLM (OpenGL Mathematics)

GLM (OpenGL Mathematics) is a header-only C++ mathematics library designed for graphics software. It is based on the OpenGL Shading Language (GLSL) specifications, meaning it uses the same naming conventions and functionality as GLSL. This allows developers familiar with GLSL to use the same mathematical logic in C++.

Key features include:

• GLSL Compatibility: Core types and functions mirror GLSL.
• Extension System: Provides additional capabilities like matrix transformations, quaternions, data packing, random numbers, and noise, following GLSL extension conventions.
• Versatility: While optimized for OpenGL, it is suitable for software rendering (raytracing/rasterisation), image processing, and physics simulations.
• Zero Dependencies: A platform-independent, header-only library.

GLM supports GLSL precision qualifiers (lowp, mediump, highp) through type prefixes instead of qualifiers. This allows trading precision for performance. By default, all types use high precision.

To use them, use the following naming convention:

• lowp_vec4 / lowp_ivec3 etc.
• mediump_vec4 / mediump_ivec3 etc.
• highp_vec4 / highp_ivec3 etc.

#include <glm/glm.hpp>

ivec3 foo(const vec4 & v)
{
    highp_vec4 a = v;
    medium_vec4 b = a;
    lowp_ivec3 c = glm::ivec3(b);
    return c;
}

GLM extends its core GLSL feature set through dedicated extension headers. To use an extension, you must include its specific header file. Once included, the extension's features are added directly to the glm:: namespace. Including an extension also automatically includes all its dependent core functionalities and other required extensions.

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>

int foo()
{
    glm::vec4 Position = glm::vec4(glm:: vec3(0.0f), 1.0f);
    glm::mat4 Model = glm::translate(glm::mat4(1.0f), glm::vec3(1.0f));

    glm::vec4 Transformed = Model * Position;
    return 0;
}

By default, GLM prioritizes constexpr support, which can disable certain SIMD optimizations. To enable the SIMD instruction code path for better performance, define the GLM_FORCE_INTRINSICS macro.

Warning: Enabling this may disable constexpr support for certain operations.

Some GLM features are considered experimental and are not enabled by default. To use these features, you must define the GLM_ENABLE_EXPERIMENTAL macro in your project.

Note: Using this macro may expose APIs that are subject to change in future releases.

GLM provides replacements for functions deprecated in the OpenGL 3.1 specification. Most of these are located in the GLM_GTC_matrix_transform extension.