如何编辑gltf锈蚀箱中的gltf数据？

Question

我正在通过编写一个我需要的终端实用程序来学习锈病。

该工具需要接受一个gltf文件，并将线性转换应用到节点和缓冲区。

现在，我正试图缩小逆绑定矩阵数据。

为此，我使用了这个箱子：

https://docs.rs/gltf/latest/gltf/

在加载了数据之后，我尝试达到这样的二进制数据：

use gltf::Gltf;

fn main() -> Result<(), gltf::Error>
{
    let gltf = Gltf::open("Assets/werewolf_animated.gltf")?;

    for skin in gltf.skins() {
        for joint in skin.joints()
        {
            println!(
                "Skin #{} has {} joint",
                skin.index(),
                joint.index(),
            );
        }

        for ibm_accessor in skin.inverse_bind_matrices()
        {
            println!("Accessor #{}", ibm_accessor.index());
            println!("offset: {}", ibm_accessor.offset());
            println!("count: {}", ibm_accessor.count());
            println!("data_type: {:?}", ibm_accessor.data_type());
            println!("dimensions: {:?}", ibm_accessor.dimensions());

            println!("buffer: {:?}", ibm_accessor.view().unwrap().buffer().source());
      
        }
    }

    Ok(())
}

如果这是C或C++，在这个阶段，我将有一个浮点数*，我将能够开始读取和写入二进制数据，把它当作一个浮点数数组。但这是生锈。

关于如何开始篡改ibm_accessor.view().unwrap().buffer().source()下的数据的任何建议

Answer 1

免责声明:我以前从未使用过glTF数据结构或glft机箱。但是，我发现了这篇文章，以及这份文件，这表明源数据可能被编码为Base64。

注：url辅助库

根据文档的说法，Source是一个枚举，有两个变体：Bin和Uri(&'a str)。

处理枚举的惯用方法是将其与之匹配：

// In the import section
use data_url::DataUrl;

// In your code
let source = ibm_accessor.view().unwrap().buffer().source();

match source {
    Bin => {
        // This case seems to only apply to .glb (binary glTF) files.
        // If it doesn't apply, maybe skip it?
        continue;
    },
    Uri(data) => {
        // Here we can handle the data which is of type `&str`
        // As mentioned in the linked documentation, this is
        // probably (?) a `data:` Base64 encoded URI, something like
        // data:application/octet-stream;base64,AAABAAIAAAAAAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAAAAAAAAACAPwAAAAA=
        // Mozilla/SimonSapin (well-known Rust dev) wrote this library
        // to handle `data:` URIs: https://docs.rs/data-url/latest/data_url/
        // let's use that.
        let url = match DataUrl::process(data) {
            Ok(url) => url,
            Err(_) => {
                // This is probably not a `data` URI? Maybe it's a https:// link or something? 
                continue;
            }
        };
        
        let (body, _fragment) = match url.decode_to_vec() {
            Ok(res) => res,
            Err(_) => {
                // The base64 was malformed!
                panic!("Or handle this error somehow?");
            }
        };
        // `body` is now a `Vec<u8>` (vector of bytes) which you can loop over.
    }
}

data_url概念证明

为了向我自己证明data_url机箱是干什么的，我做了这个小POC

Carto.toml

[package]
name = "data-url-test"
version = "0.1.0"
edition = "2021"

[dependencies]
data-url = "0.1.1"

main.rs

use data_url::{DataUrl, mime};

fn main() {
    // URL is from https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_005_BuffersBufferViewsAccessors.md
    let data = "data:application/octet-stream;base64,AAABAAIAAAAAAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAAAAAAAAACAPwAAAAA=";
    let url = match DataUrl::process(data) {
        Ok(url) => url,
        Err(e) => {
            eprintln!("Error {:#?}", e);
            return;
        }
    };
    let (body, _fragment) = match url.decode_to_vec() {
        Ok(res) => res,
        Err(_) => {
            // The base64 was malformed!
            panic!("Or handle this error somehow?");
        }
    };
    println!("body {:?}", body);
}