CPU Rasterizer

The cpurast is a software rasterizer written from scratch. Basically, it is a very simple and limited imitation of a graphics library (such as OpenGL), yet it performs all graphical computations on the processor. This approach is slower than utilizing a graphics processor but more flexible since it has no additional driver and hardware requirements. Furthermore, some concepts like packing and transferring data to the graphics processor are entirely omitted. Hence, the final use should be easier. Yet surprisingly, cpurast comes with some advanced features.

This project was created during my master's studies. I chose this assignment because I wanted to get an idea of what could be inside a real graphics processor so that it supports the functions of graphics libraries. When I started, I had just a little experience with computer graphics, so I had to study a lot. Feel free to take a look at the used sources from which I have gained my knowledge.

Features

• Draws points, lines, and triangles
• Integer-based rasterization
• Interpolation of vertex attributes
• Programmable vertex and fragment shaders
• Early depth testing
• Viewport rendering
• Normalized coordinates and colors, both compatible with OpenGL
• Cross platform, minimal dependencies

Repository Structure

• cpurast - this rasterization library
• cpurast/sdl_canvas - SDL canvas to draw on
• examples - example programs utilizing cpurast
• examples/line - dancing line with various angles and sizes
• examples/triangle - colored triangle with a resizable window
• examples/square - colored square utilizing squared viewport
• examples/grid - grid of randomly colored rectangles
• shaders - example cpurast shaders

How to Run Examples

Requirements to run examples:

• SDL2 library
• CMake tools
• A C++ compiler

Building examples that use cpurast:

cd cpurast
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE="Release" ..
make -j

Running a triangle example after building:

./examples/triangle/triangle

How to Use as a Library

Minimum requirements to use the library:

• A C++ compiler

What may be useful:

• Delivered CMake build system
• Delivered examples of use

It is suggested to start with an existing example, copy it to a new example directory, and start customizing it. Later, after some experience with using and building cpurast, the created program may be used as the foundation of a new project.

Using a Custom Canvas

This library comes with SDL canvas to draw on:

#include "cpurast.hpp" // cpurast core
#include "cpurast_sdl.hpp" // cpurast SDL canvas

SDL_Surface* surface = /* pointer initialization */;
...
std::unique_ptr<cr::canvas> cr_canvas;
...
cr_canvas = std::make_unique<cr::sdl_canvas>(surface);

You may also create and use a custom canvas:

#include "canvas.hpp" // cpurast canvas interface

class custom_canvas : public cr::canvas
{
...
}

#include "cpurast.hpp" // cpurast core
#include "cpurast_custom.hpp" // cpurast custom canvas

std::unique_ptr<cr::canvas> cr_canvas;
...
cr_canvas = std::make_unique<custom_canvas>(/* custom constructor */);

If you created a custom canvas, please consider contributing to cpurast.

Used Sources

The most important sources, in chronological order:

• https://db.in.tum.de/teaching/ss20/c++praktikum/slides/lecture-11.pdf
• https://trenki2.github.io/blog/2017/06/02/using-sdl2-with-cmake/
• https://benedicthenshaw.com/soft_render_sdl2.html
• https://www.youtube.com/watch?v=dUlWUcugA9A
• https://www.khronos.org/opengl/wiki/Default_Framebuffer
• https://registry.khronos.org/OpenGL-Refpages/gl4/html/glViewport.xhtml
• https://learnopengl.com/Getting-started/Hello-Triangle
• https://github.com/ssloy/tinyrenderer/wiki/Lesson-1:-Bresenham%E2%80%99s-Line-Drawing-Algorithm
• http://www.sunshine2k.de/coding/java/TriangleRasterization/TriangleRasterization.html
• https://www.geeks3d.com/20130514/opengl-interpolation-qualifiers-glsl-tutorial/

I have also used official CMake, SDL, and C++ documentation.

Todo

• Recycle some examples into 3D examples
• Perspective correct interpolation
• Improve clipping for lines, triangles
• Add support for texturing
• Add support for textures with transparency
• Add support for a 3D model format
• Add support for backface culling
• Add support for shadows
• Add support for drawing arrays of primitives
• Add demonstration screenshots to readme