joshb / triangleraster

A graphics demo written in C++ that demonstrates triangle rasterization.

triangleraster

This is an SDL-based demo written in C++ that features a simple triangle rasterization algorithm. It was originally created to accompany this article.

This demo has been tested on Ubuntu 18.10. To build it, make sure that you have the SDL2 development package installed and run 'make'. This will create an executable called 'triangleraster' that you can then run. Press the 'Escape' key to exit the demo.

License

Copyright © 2009-2018 Josh A. Beam
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

triangleraster's Issues

Failing on triangles with both short sides on the left

Hey Josh,

thanks a lot for the code, I'm using it to rasterize triangles in a Delaunay triangulation. I discovered an issue in the case of triangles with both short sides on the left; the spans in this case reach from x1 to x2, where x1 > x2 and so no pixels are drawn in:

triangleraster/Rasterizer.cpp

Line 118 in 263d823

for(int x = span.X1; x < span.X2; x++) {

The failure cases are exemplified in the image below (black triangles: failure case, gray: successfully rasterized)

I've fixed it by simply swapping the range limits if x2>x1.