Will I be able to port my library to BGFX if I'm using OpenGL 4.5+ features?

[dantamont]

Hi folks, I want to start by saying that this is an incredibly impressive library. @bkaradzic , I hope that somebody somewhere is paying you well.

I am currently using OpenGL 4.5 for my rendering pipeline, and make use of the following for all of the fancy things I've wanted to do:

• Uniform Buffer Objects
• Shader Storage Buffer Objects
• cubemap texture arrays
• 2D texture arrays
• geometry shaders,
• compute shaders
  By all of these powers combined, I can render to multiple cameras at once using off-screen framebuffers, create custom effects like SSAO/bloom, and render multiple point/directional/spot lights via my GLSL shaders, all through a clustered forward rendering pipeline.

However, I really want the portability BGFX offers. Is it possible to take all of this stuff I have and convert it to BGFX? I'm worried that I may be too deep down the OpenGL rabbit hole.

[bkaradzic]

Yes, almost all is possible, check examples: https://bkaradzic.github.io/bgfx/examples.html

The only thing is not supported are geometry shaders. Also there is no plan at all to support geometry shaders.

These concepts you listed are slightly different, and not 1:1 mapping with GL API, but all can be achieved.

[dantamont]

Thanks again, that's great insight. I'd have to read up on how to use ARB_shader_viewport_layer_array, but it sounds like it's made for exactly my situation. You're saying that this is all accessible through your API? If so, I'm definitely going to make a switch to BGFX, and would love to know how much work it took to put together such a robust framework.

[bkaradzic]

I'd have to read up on how to use ARB_shader_viewport_layer_array, but it sounds like it's made for exactly my situation. You're saying that this is all accessible through your API?

It's accessible via shader. But it's recently added on someones request, but I haven't spend enough time testing it... Which means you might run into issues which should will be solved then.

and would love to know how much work it took to put together such a robust framework.

bgfx is just compilation of my experience of working on AAA games.

[dantamont]

That all sounds great! I'll almost certainly switch over to BGFX within the next year or two. Would you happen to have any example use cases for how I would use ARB_shader_viewport_layer_array? I'd like to replace my geometry shaders before switching over to BGFX. I'm hoping that will make the process more painless.

Thanks again!

[pezcode]

Basic idea would be:

• bind cube map as framebuffer as usual
• draw your object with 6 instances (glDrawElementsInstanced most likely)
• in your vertex shader: gl_Layer = gl_InstanceID;
• each instance now outputs to a different cube map side

[dantamont]

Thanks @pezcode , I'll give that a go whenever I port stuff over to BGFX! That'll take a while, so I'm holding off until I actually push out a game ;)