Raytracing + Imgui

[plucky stump]

Hey can someone point me in the right direction on how to use ImGui along side a raytracing pipeline.

So I have a raytracing renderer which init Vulkan and all the stuff for the raytracing to work, but now I would like to have Imgui too to display my UIs, but Imgui require a render pass that i dont have since I'm using a raytracing pipeline, so I tried to create a dummy one but it keep crashing.
Do I need two pipeline ? how does that work exactly ?

Thanks for your help 🙂

[rigid prairie]

you don't need a "dummy" renderpass, you need an actual renderpass

and yes you need multiple pipelines

[plucky stump]

Yeah that what I though, that why I'm asking here.
I don't really understand how that will work, do I have to create 2 command buffer one for each render method and fire them at the same time ?

[rigid prairie]

you don't need multiple command buffers, that's unrelated to this

[plucky stump]

So how do I send the command to render the UI ?

I need to bind the pipeline right ?

[rigid prairie]

you have a few scenarios to pick:

• you render your RT workflow to a offscreen image
  you do your UI renderpass and draw your RT image as a fullscreen texture
• you render your RT workflow to the swapchain
  you do your UI renderpass with load op load

[rigid prairie]

you seem to be thinking command buffers only can do one thing?

[plucky stump]

Euh.. I'm pretty new 😄 But I bind a lot a thing to my command buffer, and I would assume that binding two pipeline would mess with my RT workflow

[rigid prairie]

they're sequential, as in they affect what comes after

[storm basalt]

see also https://github.com/nvpro-samples/vk_raytracing_tutorial_KHR

[plucky stump]

My goal would be to have my Imgui UI containing a viewport where my RT frame will be drawned into

[storm basalt]

they do that exact thing in the tutorial I linked

[rigid prairie]

then you would be doing the first scenario

[plucky stump]

which one ?

[storm basalt]

any of them but the _simple one is the simplest

[plucky stump]

oki thanks i'll look into it

[storm basalt]

I'd also recommend going on the tutorial page itself here

it's sort of a series, and lots of these apps build on what the previous apps established

[plucky stump]

I believe the issue with those is that they're using rasterization so they just have to use the already existing render pass, where in my case I dont have any graphic pipeline

[storm basalt]

no?

they have a rasterization fallback but you can just ignore that and imagine it doesn't exist

[plucky stump]

(also they're using nvvk, which make it quite more difficult to understand what's going on)

Oki I'll look more deeper

[rigid prairie]

the main thing you need to do is render to a offscreen texture
then you can follow any tutorial on how to draw a image with your UI toolkit of choice