# line

**Repository Path**: weiqifa/line

## Basic Information

- **Project Name**: line
- **Description**: 2D Line Drawing Samples in C
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-02-26
- **Last Updated**: 2021-02-26

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## 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.