openjpeg VS rend3

mkdir ~/install cd ~/install wget https://github.com/uclouvain/openjpeg/archive/master.zip unzip master.zip cd openjpeg-master/ mkdir build cd build cmake -DCMAKE_BUILD_TYPE=Release .. make sudo make install sudo make clean cd

Details here, if you like reading bug reports. It took the cooperation of developers at all four levels to fix this. I wrote a test project to reproduce the problem, the jpeg2k developer was able to reproduce the problem under valgrind (a tool for finding bad pointer references in C, seldom needed by Rust users), an OpenJPEG developer fixed the C code, and everybody in the chain updated versions. Thanks to everyone who had a part in this.

> The whole file is effectively a write-what-where primitive2. In addition to that, the Count Info Table is not bounds checked either...

File formats like that, with many offsets in the file, are troublesome. There used to be more formats like that. Microsoft Word .doc is the classic example.

OpenJPEG 2000 has a similar problem. I just hit that yesterday.[1] Valgrind is finding references to un-initialized data which affect control flow, and running the JPEG decoder on valid but truncated files (which is allowed) is causing bad memory reference crashes and errors.

New formats like this are rare. People have learned. A modern exception is Unreal Engine 5's Nanite has much offset data, and there may be an attack surface there for hostile game content. Nanite is a way to store a graphics mesh with both multiple levels of detail and common submeshes. It's a hierarchy of directed acyclic graphs, flattened into a linear file with offsets. And, sure enough, there are many crash reports. At least Unreal provides a validator for the format.

(If only C/C++ had slices in the language. Most of the things for which pointer arithmetic is used can be done with slices. Slices really are pointer arithmetic, with sanity.)

[1] https://github.com/uclouvain/openjpeg/issues/1459

JPEG 2000 decoder crashes Trying to read files at reduced resolution crashes with memory access errors. This is jpeg2k (Rust) calling jpeg2000-sys (Rust glue to C foreign function interfaces) calling OpenJPEG (all C). The problem can now be reproduced at the C level alone, under Valgrind. The developers of the top two levels have been very helpful, but the trouble is down in the rather painful C code at the bottom. The OpenJPEG maintainers are way behind on fixes, despite being funded.

It certainly was a risk in 2013, when the open source libraries were slow and riddled with bugs. Today, there are two stable, well maintained and fast open source libraries available:

https://github.com/uclouvain/openjpeg

The WGPU people are still working through lock conflicts in that area. The idea with Vulkan land is that you should be able to load content while rendering is in progress. For that to be useful, all the layers above Vulkan also have to have their locking problems hammered out. Most open source game engines don't do that yet. Unreal Engine and Unity do, which is why you pay for them for your AAA title.

[1] https://raw.githubusercontent.com/BVE-Reborn/rend3/trunk/exa...

[2] https://github.com/BVE-Reborn/rend3/blob/trunk/examples/scen...

[3] https://video.hardlimit.com/w/sFPkECUxRUSxbKXRkCmjJK

The big problem I have with bevy here is that they seem to be very much against bevy being reusable across the ecosystem. Every feature has to be bevyfied into an ECS thing. There's no way one can use bevy_input for input handling outside of bevy, or bevy_audio for audio, or bevy_render to get a 3d renderer like https://rend3.rs/. The Rust ecosystem would've been so much better off if bevy wasn't creating a walled garden and draining insane amounts of effort just for itself, but say instead used rend3 for its rendering, so that other efforts in rust gamedev didn't have to reimplement everything from scratch.

We have our own engine. There aren't really full engines available in the Rust ecosystem. Bevy attempts to fill this, but it's far from being feature complete. There's also https://fyrox.rs/, but that's also work in progress. There's also https://rend3.rs/ which is just a 3d renderer, so you'll need to build the rest of the engine yourself.

That's been fixed. It was one of those things where a complicated workaround for Rust's ownership rules, one that required maintaining internal consistency between multiple tables, was inconsistent.

Rend3 crashes The library's internal memory allocator for GPU objects is losing objects and panicking. This seems to be a race condition that comes up once you get past displaying static scenes and start having moving objects. Rend3 has one overworked main developer. If you're qualified to work on GPU-level stuff, which I am not, that project could use help.

I personally use Rend3, ability to use WGPU to make my own render effects, but I still get to build my own engine around it, although I'm waiting for the vertex-pulling branch to be merged before I really get going