t

Documentation

A software graphics library written in C++, originally for the terminal.

For example, rendering the original Utah teapot (triangulated at 3488 tris) in 125 FPS:

💻 Example

The below example creates a cube with its normals mapped to its colors, then animate it rotating in a while loop. The cube's rotational speed might be slightly different depending on your CPU.

#include "t.hpp"
#include <iostream>

using namespace t;

int main() {
  auto box = Box(1, 1, 1);
  auto material = NormalColor();
  auto mesh = Mesh(box, material);

  const auto width = 80;
  const auto height = 24;

  auto scene = Scene();
  auto camera = PerspectiveCamera(M_PI / 4, static_cast<double>(width) / height,
                                  0.01, 10);
  camera.translate(0, 0, 1);

  scene.add(mesh);
  scene.add(camera);

  auto renderer = Rasterizer();
  auto renderTarget =
      RenderTarget<double>(width, height, TextureFormat::RgbDouble);

  while (true) {
    mesh.localRotation.x += 0.002;
    mesh.localRotation.y += 0.001;

    renderer.render(scene, camera, renderTarget);

    std::cout << "\x1b[H"; // Set terminal's cursor position to top-left corner

    for (int j = 0; j < renderTarget.height; j++) {
      for (int i = renderTarget.width - 1; i > -1; i--) {
        int index = (i + j * renderTarget.width) * 3;

        auto r = renderTarget.texture.image[index];
        auto g = renderTarget.texture.image[index + 1];
        auto b = renderTarget.texture.image[index + 2];

        std::cout << "\033[38;2;" << static_cast<int>(r * 255) << ";"
                  << static_cast<int>(g * 255) << ";"
                  << static_cast<int>(b * 255) << "m@\033[0m";
      }

      std::cout << "\n";
    }
  }
}

🏃 Getting started

Clone:

git clone https://github.com/cszach/t.git

Compile:

cmake -B build .
cmake --build build

Run:

cd build/bin
./cube

Test:

cd build
ctest

🫖 Demos

• cube.cpp: the rotating cube example from above,
• cornell_box.cpp: the classic Cornell box rendered with Blinn-Phong shading,
• teapot.cpp: a spinning animation of the triangulated original Utah teapot (3488 tris) with normal material, with an FPS counter at the top-left (might not be visible due to the output being constantly overwritten); useful for testing performance.
• teapot2.cpp: a blue Utah teapot with ambient lighting and a point light traveling in a circle. Showcases specular highlights;
• triangle.cpp: a simple triangle printed to the terminal screen. Demonstrates how to set up a custom 3D geometry.

For all demos, please make sure your terminal is at least 80 cells wide and 24 cells high. You can go into the source code and change the width and height values.

📜 Specification

Cameras

• Project matrices are expected to transform view space into clip space (NDC).
• The normalized device coordinates (NDC) range from \f$(-1, -1, -1)\f$ to \f$(1, 1, 1)\f$, and the bottom left corner is \f$(-1, -1, z)\f$.

Math

• Matrix-vector multiplication use post-multiplication notation.
  • That means B = MA where M is a matrix, and A and B are vectors.
• Like WebGL, matrix addition, subtraction, and division are component-wise, but multiplication is not.

Primitives

• Right-handed coordinate system
  • Positive Y is up.
  • Z for depth. Positive Z is generally considered "towards the viewer".
• Each Mesh has a shape (geometry) and a look (material).
• An Object3D is either a Mesh, a Scene, or a group of any Object3D, and has a local position, rotation, and scale.
• The vertex data maybe indexed or not.

Renderers

Rasterizer

• Forward rendering pipeline with vertex and fragment shading.
• One "draw call" for every mesh.
• Depth tests use less-than-or-equal-to comparison; this means that the higher the Z value, the more "far-away" the object is.

🚧 To-do's

• Directional light
• Spot light
• Shadows
• OBJ import
• Post-processing
• Better name?

Fix-me's

• The camera's lookAt's target is currently hard-coded to the zero vector.
• The x-axis in the render target appears to be flipped.
• Camera's near and far values are currently ignored.

Will not be worked on

I will focus my time and efforts on another renderer, but here are some ideas for potential contributors. Feel free to tell me about your forks.

• Alpha color
• Color blending
• Quaternions
• Stencil buffer
• SIMD
• Image textures
• More geometries
• More materials
• UVs
• Deferred rendering
• Parallel computing
• Ray tracing
• Wider ASCII character set
• Interactive 3D in the terminal demo
• More coverage for unit tests
• Robust Euler rotation computations
• Custom varyings

🙌 Acknowledgements

API design is inspired by three.js.

The rendering pipeline is inspired by WebGL and WebGPU.