I am using vulkan (ash) to render a scene.
The rendering algorithm first does a raytracing pass (using the traditional pipeline not the NV extensions) then it renders a few frames normally.
On Nvidia it renders fine, on AMD I am experiencing a flicker.
The draw structure is:
- Raytrace
- Render 6 meshes with 6 draw calls
If I render that in immediate mode, I get flickering, if I do so in FIFO mode I don't. In immediate mode, if I put the thread to sleep in between the raytracing call and the mesh calls I get flickering no matter how slow the sleep is even at a 1 second sleep the flcikering occurs. The pattern of the flicker is 4 calls rendered normally, 2 calls the RT image is the only thing rendered, as if it had been called after the 6 regular mesh calls, even though it;s issued before them.
All f this suggests a synchronization bug. The issue is I have no idea what I forgot to do.
Each draw call is drawing to a swapchain image, each draw call has this structure:
Set up uniforms, desciptor sets, pipelines...
Create a fence
Submit draw command to queue signaling fence
Wait for fence
Wait for device
Delete fence
I am currently doing that at the end of every single one of the 7 calls. What did I forget to sync? What barrier am I missing?
I am using the passless rendering extension, so I don;t have any render passes. I might need an image barrier on the swapchain as a consequence but I don;t know if, and what it would need to be.
