Working on a common scenegraph for OSG and VSG

[VasanthBalguri]

Hi,

I am working on an application which can render using opengl or vulkan for compatibility. Here for opengl I will use OSG and for Vulkan use VSG. I am going through the osg2vsg codebase now to learn more about, but before I start, I would like to know if I am headed in right direction, this is what I want to achieve:

• A scenegraph datastructure which is serilaziable.
• This datastructure will be parsed by osg and vsg and generate its respective scenegraphs. So that my application will seamlessly read this format of data and render the scenegraph
• I will also embed metadata into this scenegraph which can be accessed by the application.

I have following doubts here:

• I want to know if my efforts placed will aligns with the mission statement of VSG? if so I will directly contribute vsg.
• I am able to understand the stateset in osg , but in vsg i am missing that clarity, there is statset mentioned vaugely, but i see examples directly adding shaders to the pipeline and adding it to scenegraph.

I am also thinking of documenting all the nodes and their purpose as well as part of this project. This will surely help other who want to get started.

[robertosfield]

Vulkan is available on all major platforms for quite a few years, going through the massive extra complexity of supporting OpenGL let alone having two scene graphs is crazy.

I strongly suggest you just focus on Vulkan, OpenGL & OSG are not being developed and only exists for backwards compatibility for old applications.

Keeping things simple and just focusing on one hardware API and one scene graph API will make your life far, far more productive.

I can't stress this enough, it's insanity to try and juggle two scene graphs and two underlying hardware abstractions layers.

If there was any sense in doing what you are suggesting I wouldn't have created the VulkanSceneGraph project, it would have made sense to add Vulkan support to the OpenSceneGraph. I tried to figure out how to do this and came away that it just couldn't be done in any practical way and performance would have been worse for both OpenGL and Vulkan usage.

It only made sense to start afresh and create a modern scene graph, with modern C++, with a modern and supported hardware abstraction layer. The VSG is far cleaner and faster than the OSG.

[VasanthBalguri]

Got it, it makes sense that having a common scenegraph is an exercise in futility, but I was asking more like if we have a common fie format, but even that seems like an exercise in futility as vulkan is more common now on all the devices.

I feel that vulkan itself is very complex and VSG does a good job in abstracting it with as much control as possible to developer, but the documentation gap between OSG and VSG is such that I am compelled to use OSG. I have learned a thing or two about vulkan and vsg. I am planning to use it in one of my applications. so maybe I can prepare some kind of documentation which can set a good foundation for newcomers to make a application from scratch.

[robertosfield]

It took decades for the OSG to accumulate the documentation is has, even then it's still not enough.

For the VSG's point in it's life cycle it has more documentation that the OSG had at the same point, so even though it's not enough it's still more than the earlier adopters of the OSG had.

If you want to use modern graphics techniques then the VSG even with incomplete documentation will be easier to use than the OSG. The OSG really is only easy when you stick to the fixed function pipeline, once you drop in full shader based application it's pretty crude compared to the VSG.

[VasanthBalguri]

Actually I am not complaining or blaming for the lack of documentation, the wiki is fairly good and discussions are also fairly productive. Maybe my tone is incorrect. What I am saying is that I will prepare some documentation/tutorial from my end and share it once done.

Also there is a steep learning curve to understand how vulkan actually works, I had to study vulkan first to appreciate VSG project. where as in OSG I jumped right in without any knowledge of opengl then figured it out as I moved along. Please don't take it as a complain, it is just an humble observation. Thanks and Regards.

[robertosfield]

As a general comment, glTF is the closest thing we have to a standardized scene graph file format. It's a poor substitute for a native serialization but at least you can multiple modelling tools and scene graphs/engines that support it.