3D Software Rasterizer in C

A CPU-side 3D renderer that takes a mesh through transformations, clipping, projection, and triangle rasterization. The graphics pipeline is implemented in C; SDL2 handles the window, input, and presentation of the final color buffer.

C99 · SDL2 · Linear algebra · Software rendering

Watch the rendering demo

From mesh to pixels

OBJ mesh → World transform → Camera space → Back-face culling
         → Frustum clipping → Perspective projection
         → Triangle rasterization → Color / depth buffers → SDL2

The interesting work is inside the renderer: matrix and vector math, clipping geometry against the view frustum, interpolating texture coordinates, and resolving visibility per pixel.

Features

• Scale, rotation, and translation matrices, plus a movable camera.
• Perspective projection and view-frustum clipping.
• Optional back-face culling.
• Wireframe, filled, and textured triangle modes.
• Perspective-correct texture interpolation and a depth buffer.
• Directional face lighting in the filled-triangle path.
• A small OBJ loader and PNG texture loading through uPNG.

Build and run

Requires a C compiler, Make, SDL2 development headers/libraries, and a graphical desktop.

git clone https://github.com/coganka/3d-rasterizer.git
cd 3d-rasterizer
make build

Scene assets are not included in the repository. Before running, provide the OBJ/PNG pairs referenced by setup() in src/main.c:

assets/runway.obj    assets/runway.png
assets/f22.obj       assets/f22.png
assets/efa.obj       assets/efa.png
assets/f117.obj      assets/f117.png

Alternatively, replace the load_mesh(...) calls with your own available files. The loader expects triangulated OBJ faces using positive vertex/texture/normal indices. Run from the repository root so relative asset paths resolve:

make run

The Makefile assumes SDL2 is on the compiler's default search path. If it is installed elsewhere, supply the flags from your SDL2 installation, for example:

cc -Wall -std=c99 -D_DEFAULT_SOURCE $(sdl2-config --cflags) \
  src/*.c $(sdl2-config --libs) -lm -o renderer

Controls

Key	Action
1 / 2	Wireframe with vertices / wireframe
3 / 4	Filled triangles / filled triangles with wireframe
5 / 6	Textured triangles / textured triangles with wireframe
C / X	Enable / disable back-face culling
W / S	Move forward / backward
A / D	Rotate camera
Arrow keys	Move camera horizontally or vertically
Esc	Exit

Where to look

Source	Focus
main.c	Pipeline stages, scene setup, input, frame loop
triangle.c	Rasterization, texture interpolation, depth testing
clipping.c	Frustum clipping and polygon triangulation
matrix.c, vector.c	Transform and camera math
mesh.c	Mesh storage and OBJ/PNG loading

Scope

This is a graphics fundamentals project with a fixed demo scene, not a general-purpose asset pipeline. Mesh and triangle buffers have fixed limits, and asset loading assumes valid input; missing files must be resolved before launching. SDL2 presents the output, while uPNG decodes textures—the PNG decoder is a third-party component, not part of the custom renderer.

The next useful improvements are bundled sample assets, explicit loader errors, and repeatable image-based rendering tests.

Third-party code

src/upng.c and src/upng.h contain uPNG, derived from LodePNG. Original copyright and license notices are retained in those files.