Software rasteriser

An implementation of the rasterisation algorithm for drawing 3D triangles using OpenGL-imitation maths.

This is a self-learning project intended to teach me how an Open-GL style renderer works behind the scenes. It is fairly closely based on the approach described at Scratchapixel, but with some modifications to use the OpenGL perspective projection matrix. A log of development can be found here.

Example output

Third party code

Included in repository:

• the CImg library. The license is contained in the vendor/cimg/ folder along with the header file.
• tinyobjloader by syoyo. The license is written at the top of the header file.

Needed for compilation:

• OpenGL Mathematics (GLM), which should be installed using Conan as described below.
• Templatized C++ Command Line Parser Library (TCLAP), which should be installed using Conan.
• text-csv, which should be installed using Conan.
• CMake.

Needed to run:

• ImageMagick or GraphicsMagick to allow CImg to output PNG files.

Building

1. Create a build folder inside the project folder.
2. In the build folder, run conan install .. --build TCLAP to install GLM, TCLAP and text-csv via Conan, and produce a CMake file.
3. Run cmake .. to produce build files appropriate to your build system (e.g. a makefile for GCC).
4. Compile according to your system (e.g. with make for gcc, or ming32-make for MinGW-GCC).

Use

Run the executable from the command line. Flags available:

• -h/--help: display command line options and exit

Loading files:

• -o/--obj: render the model in the specified Wavefront .obj file (otherwise renders a square)
• -l/--lights: (required) specify CSV file containing a list of directional lights in the format dir_x,dir_y,dir_z,intensity,red,green,blue (all interpreted as floating point numbers)

Render settings:

• -x/--width: width of the output image (pixels)
• -y/--height: height of the output image (pixels)
• -s/--spin: instead of outputting the frame and depth buffers as images, display a window with the model rotating at 1 radian/sec about the y axis
• -f/--flat: disable smooth shading, and use calculated face normals instead of given vertex normals
• --wind-clockwise: specify that triangles should be interpreted to use a clockwise rather than anticlockwise winding order

Transform model:

• --scale: scale the model uniformly by a factor
• --dx, --dy, --dz: displace model in X, Y and Z directions by distance
• --rx, --ry, --rz: rotate model according to YXZ Tait-Bryan angles in radians

If -s is not set, two images will be output. frame.png is the rendered image, and depth.png is the depth buffer.