Hello everyone
Today I did a very simple test, with a glass bottle, very basic light and one texture for displacement on the bottle. I did the scene in houdini and then render it with karma. Then I transfered the scene via usd to blender, adapted materials, and render the same scene. For a better comparison, I render the scene in 5000x6250px (a resolution I often use in my work).
I have a threadripper 3970x and rtx 4090

- Karma : 41sec
- Karma with Crypto Object AND Material : 1min43sec

- Blender Cycles : 24sec
- Blender Cycles with Crypto Object AND Material : 32secs
- Blender Cycles without tiling render (since we don't have it per default in karma I think) : 29secs

I always render with at least crypto, honestly the render time difference is huge.
I want to switch to Houdini/Karma with all my heart, but honnestly, as a freelancer, it's not possible for the moment, it's to slow (or I forget to setting something ?)

Of course the goal is not to say that Blender is better than Houdini, I much prefer the solaris workflow, Copernicus etc, and I understand that as medium/big studio they can absorb the extra rendering time, but for me, as freelancer, there is no way that I can... I know Karma is a very young render engine too.

Am I the only one who find Karma slow ?
Is there anyone who knows if Sidefx team will focus on karma render speed ?
I share the Blender and Houdini file if you want to try



Blender render :


Houdini render :

If you can, post the scene file? So that others may dissect it and give hints on possible setting tweaks.

What protozoan said. There's also some sketchy stuff going on with the glass shading in the Karma render.

I just update the post, you can find both the blender and the houdini file

No one :p ?

I guess, Karma needs huge improvements also in interactivity, moving lights or objects is just very laggy.

philippepetitpas
No one :p ?

Both same resolution of 5000 x 6250 and the render settings you defined in the project:

Blender 4.1 GPU: 02:02
Houdini 20.5.361 Karma XPU: 00:50

Threadripper 2990 / GTX 4090

I think you have something wrong with your blender settings. Make sure you have selected optix, and only selected your gpu (in my computer, when i select both my gpu and cpu it's slower)

How long does it take to render using only GPU?
You can disable the CPU by setting this environment variable

KARMA_XPU_DISABLE_EMBREE_DEVICE = 1

I played around with the Houdini scene a bit. It's strange how the displacement doesn't work at first: the dicing looks like it's 0.2 or something instead of 0.8 and the displacement is heading off to the right. Putting in a new dicing number, say 1.0 instead of 0.8, seems to immediately fix that. But the displacement only fixes itself randomly after putting a bunch of different numbers in the scale parameter. In my last test it was wrong at 0.0025, 0.1, 0.01, 0.002, but then suddenly it was correct at 0.003 and then works fine at all other values after that.

Antti1999
How long does it take to render using only GPU?
You can disable the CPU by setting this environment variable

KARMA_XPU_DISABLE_EMBREE_DEVICE = 1

Yes I tried, it’s a bit longer when I’m using only gpu.

BrianHanke
I played around with the Houdini scene a bit. It's strange how the displacement doesn't work at first: the dicing looks like it's 0.2 or something instead of 0.8 and the displacement is heading off to the right. Putting in a new dicing number, say 1.0 instead of 0.8, seems to immediately fix that. But the displacement only fixes itself randomly after putting a bunch of different numbers in the scale parameter. In my last test it was wrong at 0.0025, 0.1, 0.01, 0.002, but then suddenly it was correct at 0.003 and then works fine at all other values after that.

Maybe it’s because of the small scale scene ? (I find that I usually have trouble with small scale scene).
But I don’t think that this have a big impact on the render time… on my computer I did some different test with different dicing, and it wasn’t affect the time by a lot

This is probably not a helpful post, and I would love to see Karma getting faster, but I cannot help but be curious about the volume of your output, where a 1 minute 43 second render at 5000x6250px is unacceptably slow. If you're rendering a significant number of images, perhaps you could set up a PDG pipeline that might help offset the added render time with significantly less manual work?

It’s unacceptably slow because it’s more than 3x slower than my usual workflow. For only 1 image it’s ok, but keep in mind that this scene is extremely simple… when I have a lot of render to do, it changes everything. If you have access to a render farm it’s ok, but it’s not the same budget.

The problem is not that karma took 1m43 to do a render, the problem is that it took 3x more time, I’m sure it’s pretty the same if I compare with octane or redshift.

And I only talk about render time, not all the bugs and laggy things when you want to light a scene properly…

philippepetitpas
It’s unacceptably slow because it’s more than 3x slower than my usual workflow. For only 1 image it’s ok, but keep in mind that this scene is extremely simple… when I have a lot of render to do, it changes everything. If you have access to a render farm it’s ok, but it’s not the same budget.

The problem is not that karma took 1m43 to do a render, the problem is that it took 3x more time, I’m sure it’s pretty the same if I compare with octane or redshift.

And I only talk about render time, not all the bugs and laggy things when you want to light a scene properly…

I understand that it's 3x slower, but it's still just 1 minute 43 seconds, which is not generally an amount of time that would be considered a dealbreaker for a 3D render, particularly at that resolution, and given that you do get a reasonably accurate viewport preview as the render coalesces that lets you make decisions before waiting out the full render time.

I don't know your workload, so I can only assume that it's a very large number of renders that you need to output that will make this time unacceptable. That's where the PDG suggestion came in - wherein that could potentially reduce the time it takes you set up each render manually, and offset thus the time delays, along with having you do less manual work.

Another thing to keep in mind is that it might not be 3x slower across the board, so check with other scenes if you're experiencing
an equivalent delta.

Meanwhile, hopefully SideFX can look into yours or similar scenes and find ways to speed Karma up.