---
title: "README"
author: "Gregory Jefferis"
output: 
  html_document: 
    keep_md: yes
---

<!-- README.md is generated from README.Rmd. Please edit that file -->



# dracor

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The goal of **dracor** is to allow decoding of the Draco compressed meshes in R. 
This is done by wrapping the [Draco](https://github.com/google/draco) C++ 
decoding library with the assistance of the [Rcpp package](https://cran.r-project.org/package=Rcpp).

The original motivation for **dracor** was decoding [neuroglancer](https://github.com/google/neuroglancer) meshes of neurons for
example as used by https://flywire.ai/.

## Installation

**dracor** is available from [CRAN](https://cran.r-project.org/package=dracor):


```r
install.packages('dracor')
```

but you can also install the development version like so:


```r
remotes::install_github("natverse/dracor")
```

## Example

This is a basic example using a sample from the draco repository


```r
library(dracor)
# get sample file from draco repository
carurl='https://raw.githubusercontent.com/google/draco/main/testdata/car.drc'
car.m3d=dracor::draco_decode(carurl)
str(car.m3d)
#> List of 2
#>  $ vb: num [1:4, 1:1856] 1.54 1.65 -1.21 1 1.57 ...
#>  $ it: int [1:3, 1:1744] 1 2 3 3 2 4 4 2 5 5 ...
#>  - attr(*, "class")= chr [1:2] "mesh3d" "shape3d"
```


[rgl](https://cran.r-project.org/package=rgl) is the most widely used R package
for 3D visualisation. By default we return meshes as rgl `mesh3d` objects, 
which can then be displayed by `rgl` or manipulated by
a range of R packages including [Rvcg](https://cran.r-project.org/package=Rvcg).

```r
# install.packages("rgl")
# convert to rgl mesh3d format
# set a nice viewpoint
rgl::shade3d(car.m3d, col='red')
rgl::view3d(theta = 60, fov=0, zoom=.7)
```

<img src="man/figures/README-unnamed-chunk-5-1.png" width="100%" />

## Some details

**dracor** is deliberately intended as a minimal decoder package without any
dependencies besides the Rcpp package. It accepts raw bytes, a file or a URL as input and can produce either an [rgl](https://cran.r-project.org/package=rgl) `mesh3d` object as output or a list containing points and 0-indexed faces. It essentially 
replicates the most basic decoding ability of the `draco_decoder` command line tool.

If you just want a result as close as possible to what the Draco library would give
then set `mesh3d=FALSE`

```r
car.m=dracor::draco_decode(carurl, mesh3d=FALSE)
str(car.m)
#> List of 2
#>  $ points: num [1:3, 1:1856] 1.54 1.65 -1.21 1.57 1.77 ...
#>  $ faces : int [1:3, 1:1744] 0 1 2 2 1 3 3 1 4 4 ...
```

## Acknowledgements 

Many thanks to the authors of:

* [Draco library](https://github.com/google/draco)
* [Rcpp package](https://cran.r-project.org/package=Rcpp)
