Is there a way to have both OpenGL viewport and Vulcan viewport open in one session or at least switch between them without restarting and changing env variables?

Thank you

Is there any difference between using Vulcan and OpenGL? I compared them and didn't notice significant differences in both appearance and performance; they both seem very similar to OpenGL.

EP nineteenma
Is there any difference between using Vulcan and OpenGL? I compared them and didn't notice significant differences in both appearance and performance; they both seem very similar to OpenGL.

They're supposed to look same, otherwise te Vulcan has failed. I believe Vulcan viewport at its current state is just SideFX trying to make a more robust, future-proof fundation for more advanced viewport features in later versions, but not something that you can just switch to and magically gain 200% performance.

I don't recall what are the visible differences, but try lots of (condensed) feathers.

How does Nvidia Studio drivers affect Vulkan?

OpenGL vs. Vulkan: What are the Key Differences? [history-computer.com]

LukeP
Is there a way to have both OpenGL viewport and Vulcan viewport open in one session or at least switch between them without restarting and changing env variables?

No, Houdini is either entirely in Vulkan or OpenGL mode. You can have two separate Houdini sessions running OpenGL and Vulkan from different shells, though.

EP nineteenma
Is there any difference between using Vulcan and OpenGL? I compared them and didn't notice significant differences in both appearance and performance; they both seem very similar to OpenGL.

There are some incremental improvements in rendering look, but that wasn't the focus for H20. Our primary goal was feature parity with OpenGL. The main reasons that Vulkan isn't exposed by default in H20 is that performance is not where we want it to be, and there are still a few missing pieces (mostly minor, but shadows are one of the more glaring missing features).

Anyway, the few imaging improvements we have are:

• Heightfields now draw in wireframe mode
  
• Lit Spheres particle mode is now perspective correct (also fixed in GL)
  
• Subdivision ribbons (aka hair) no longer has cracks between subd segments (also fixed in GL)
  
• Feathers look much nicer and render faster in Vulkan
  
• Lighting is always done with the deferred renderer now, which is generally more accurate (HQ Lighting in GL). This is still very much a work-in-progress in H20.
  

raincole
They're supposed to look same, otherwise te Vulcan has failed. I believe Vulcan viewport at its current state is just SideFX trying to make a more robust, future-proof fundation for more advanced viewport features in later versions, but not something that you can just switch to and magically gain 200% performance.

Well said, that's very much how we see it. Vulkan really helps in cases where there is a lot of unique geometry to be displayed, like a very large scene without much instancing use. It's much less CPU-intensive that OpenGL when issuing draw calls, and once we thread the viewport updates and renders, these scenes should see a decent performance boost. We are also taking the opportunity to reevaluate some of the ways we've been rendering certain elements and improving the shaders for those, which is independent of the API. There's still some outstanding work to be done there, especially for polysurfaces, so Vulkan will gradually overtake GL as that work is completed.

At the end of the day, your GPU hardware hasn't changed, so anything that was GPU bound before (instancing millions of cubes, for example) will remain GPU bound in Vulkan.

Werner Ziemerink
How does Nvidia Studio drivers affect Vulkan?

You need at least Nvidia 470 on Linux or 473 on Windows, both of which are far below our recommended version of 535 (for Karma XPU). Later versions add more Vulkan extensions, but unlike OpenGL and DirectX drivers, the Vulkan driver is very thin. Optimization is the developer's problem, not the driver's. So there's very little improvement, performance-wise, in different driver versions. The exception might be a Vulkan extension that enables us to use a more performant approach to rendering.

Just tested latest Houdini 20.5.348 and OpenGL crushed Vulkan.

Grid SOP with 13000*13000 wired into a Mountain SOP.

GL viewport could rotate around real time smooth like butter. Vulkan viewport was choking on it.


CPU = 7800x3d
GPU = RTX 4070 Ti Super

Windows 11 fully updated and latest Nvidia studio drivers.

This topic covers it more in depth.

https://www.sidefx.com/forum/topic/96922/?page=1#post-426078 [www.sidefx.com]

Wren
Just tested latest Houdini 20.5.348 and OpenGL crushed Vulkan.

Grid SOP with 13000*13000 wired into a Mountain SOP.

GL viewport could rotate around real time smooth like butter. Vulkan viewport was choking on it.


CPU = 7800x3d
GPU = RTX 4070 Ti Super

Windows 11 fully updated and latest Nvidia studio drivers.

I wasn't able to do a 13000x13000 grid on my workstation (ran out of memory in both cases), but 8000x8000 was fine so I tested with that. GL headlight is faster than Vulkan as we haven't special-cased the headlight for Vulkan yet. Once we do, it should be about as fast as Vulkan's No Lighting mode. We have a few more missing bits to work through first, but the fast-headlight change will be backported to 20.5 when it's implemented.

If I add a point light to that scene and switch GL to HQ lighting mode, which would be a more fair comparison, then on my system (linux, Quadro A5000), GL and Vulkan have roughly the same performance, with Vulkan taking 3ms less time.

When can we hope for the Vulkan VP to (a) have OpenGL feature parity (b) be at least as fast as OpenGL viewport?

In many cases now, Vulkan is comparable to GL in performance. There were some bad cases that we've worked on for the first production build where some things were unacceptably slow (eg point/sprite rendering). Other improvements may take slightly longer, such as parallel drawing (observed 30% less time to draw complex scenes). The main outstanding issue is the difference between GL normal quality lighting and Vulkan lighting, which we have a few ideas on the burner for (such as fast-headlight above).

In terms of parity, the todo list is down to rather uncommonly used features (eg. Fog, onion skinning). We'll continue to backport those as they are completed, so you won't need to wait until the next release for them.

If you see something that is missing in vulkan or appears to be running slower than it ought to, please submit a bug. We are working through those fairly quickly.

malexander
I wasn't able to do a 13000x13000 grid on my workstation (ran out of memory in both cases), but 8000x8000 was fine so I tested with that. GL headlight is faster than Vulkan as we haven't special-cased the headlight for Vulkan yet. Once we do, it should be about as fast as Vulkan's No Lighting mode. We have a few more missing bits to work through first, but the fast-headlight change will be backported to 20.5 when it's implemented.

If I add a point light to that scene and switch GL to HQ lighting mode, which would be a more fair comparison, then on my system (linux, Quadro A5000), GL and Vulkan have roughly the same performance, with Vulkan taking 3ms less time.

Thanks! That's great news!



ps. Side note I'm very impressed how many polys 20.5 Houdini GL can handle.