Vertex Shader processes individual vertices, converting 3D coordinates and performing basic attribute manipulation.

Primitive Assembly collects output vertices and forms them into specified primitives like points, lines, or triangles.

Geometry Shader takes primitive sets and can generate additional primitives or shapes.

Rasterization maps primitives to screen pixels, generating fragments for the fragment shader and performing clipping to discard off-screen pixels.

Fragment Shader computes the final color of each pixel, incorporaitng lighting, shadows, and other scene data.

Alpha Testing and Blending evaluates depth and transparency values, blending fragments and determining final pixel visibility.

Vertex Data and Normalized Device Coordinates

Processed vertex coordinates exist in Normalized Device Coordinates (NDC), where x, y, and z values range from -1.0 to 1.0. Coordinates outside this range are clipped.

float vertexData[] = {
    -0.5f, -0.5f, 0.0f,
     0.5f, -0.5f, 0.0f,
     0.0f,  0.5f, 0.0f
};

Vertex Buffer Objects (VBO)

VBOs store vertex data in GPU memory, enabling efficient bulk data transfer instead of per-vertex CPU-to-GPU communication.

Vertex Array Objects (VAO)

VAOs define how to interpret vertex data from VBOs, specifying data layout, strides, and attributes like position, UV, or normals. A single VAO can reference multiple VBOs.

Element Buffer Objects (EBO)

EBOs (or Index Buffer Objects) store indices to reuse vertices, reducing redundancy. For example, a rectangle can be drawn with four vertices instead of six by using indices.

float rectVertices[] = {
     0.5f,  0.5f, 0.0f,  // top right
     0.5f, -0.5f, 0.0f,  // bottom right
    -0.5f, -0.5f, 0.0f,  // bottom left
    -0.5f,  0.5f, 0.0f   // top left
};

unsigned int indices[] = {
    0, 1, 3,  // first triangle
    1, 2, 3   // second triangle
};

Example Vertex Shader

#version 330 core
layout (location = 0) in vec3 vertexPosition;
void main() {
    gl_Position = vec4(vertexPosition, 1.0);
}