https://github.com/miloyip/line

2D Line Drawing Samples in C
https://github.com/miloyip/line

graphics-programming graphics2d rendering-2d-graphics

Last synced: 9 months ago
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2D Line Drawing Samples in C

• Host: GitHub
• URL: https://github.com/miloyip/line
• Owner: miloyip
• Created: 2017-10-29T10:37:48.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2022-01-08T13:07:50.000Z (about 4 years ago)
• Last Synced: 2025-04-02T04:02:31.769Z (9 months ago)
• Topics: graphics-programming, graphics2d, rendering-2d-graphics
• Language: C
• Size: 773 KB
• Stars: 201
• Watchers: 15
• Forks: 34
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

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README

          
# 2D Line Drawing Samples

This project contains C source code for drawing 2D lines by different techniques.

All samples output PNGs with [svpng](https://github.com/miloyip/svpng).

License: public domain.

## Bresenham

The fundamental line drawing algorithm by Bresenham [1], based on [rosetta code](https://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#C).

![line_bresenham.c](line_bresenham.c)

![ ](line_bresenham.png)

![ ](line_bresenham_zoom.png)

## Sampling

Represent lines as capsule shapes, in order to support real-valued coordinates and variable width.

![line_sampling.c](line_sampling.c)

![ ](line_sampling.png)

![ ](line_sampling_zoom.png)

## Anti-aliasing by super sampling

Simple anti-aliasing with 5x5 super sampling.

![line_supersampling.c](line_supersampling.c)

![ ](line_supersampling.png)

![ ](line_supersampling_zoom.png)

## Anti-aliasing by signed distnace field

Using signed distnace field (SDF) of capsule shape to perform anti-aliasing with single sample per pixel.

![line_sdf.c](line_sdf.c)

![ ](line_sdf.png)

![ ](line_sdf_zoom.png)

## SDF optimization with AABB

Use AABB of capsule to reduce the number of samples. Render shapes into the buffer individually with alpha blending.

![line_sdfaabb.c](line_sdfaabb.c)

![ ](line_sdfaabb.png)

![ ](line_sdfaabb_zoom.png)

## Visual comparison

![ ](line_montage_zoom.png)

## Performance comparison

~~~

$ make test

gcc -Wall -O3 -o line_bresenham line_bresenham.c

gcc -Wall -O3 -o line_sampling line_sampling.c

gcc -Wall -O3 -o line_supersampling line_supersampling.c

gcc -Wall -O3 -o line_sdf line_sdf.c

gcc -Wall -O3 -o line_sdfaabb line_sdfaabb.c

time ./line_bresenham

        0.03 real         0.02 user         0.00 sys

time ./line_sampling

        1.93 real         1.91 user         0.00 sys

time ./line_supersampling

       47.06 real        46.85 user         0.10 sys

time ./line_sdf

        2.00 real         1.98 user         0.00 sys

time ./line_sdfaabb

        0.03 real         0.03 user         0.00 sys

~~~

## Final notes

1. These samples are only for illustrative purposes.

2. Line clipping are not performed.

3. The SDF AABB sample can be further optimized by tigther quaduraliteral bounds.

## References

[1] Bresenham, Jack E. "Algorithm for computer control of a digital plotter." IBM Systems journal 4.1 (1965): 25-30.