Branched vs. unbranched Pathtracing in SF



  • @eclark1849

    All images here are Superfly. For my findings it does not matter if you use GPU or CPU, from what I've seen so far.

    I've rendered images with CPU (Ryzen 1700, 15 threads) and GPU (Nvidia GTX 780). The GTX is faster most of the time, but the speed differences between BPT and PT are similar.

    My working theory is that you will get lesser noise in the same time when you use PBT. If you use it in the right way.

    You will need fewer samples with BPT, so please use the render time to compare the results.


  • Poser Ambassadors

    I'd be interested to see the results after setting maximum bounces to 16 and re-testing.



  • @bantha Looks like it's also darker. Could that be what's making it less grainy? Not complaining, by the way. It looks great.



  • 0_1517671424586_Comparison4.png

    Your wish is my command. The PT render took a bit longer and has less noise on the bathtub. The BPT render looks like it's antialiased, the edges are much less jaggy.

    PT: 262 sec. 35 samples, BPT 206 sec. 15 samples

    With Maximum Bounces = 16, the reflection on the floor is much stronger in PT then in SPT.



  • BPT on GPU crashes every time when it gets to the first tile with transmapped hair. Remove the hair and no crash. Odly enough it does not crash on eyelashes.



  • 0_1517676396747_hair.png

    @ghostship
    I did not encounter this problem yet. Transmapped hair often needs more transparent bounces, though.

    This is a real quick, an old scene. Agent hair, V4, EZSkin3 for Skin and Hair. Rendered on GPU without any problems. BPT, 15 samples.



  • Settings:
    0_1517676812674_Settings.png



  • By the way, could someone correct "Branched" in the title?



  • Things do look better with BPT enabled but it's highly unstable using CUDA unfortunately. Sometimes I can get lucky and a render with a single figure will finish but most times something will crash, either my display drivers or poser.

    Click on that "i" in the render options when you select BPT and your video card, it warns you that BPT should be disabled while using GPU rendering.



  • I do admit that most of my test renders are pretty simple, but I did not experience a crash up to now. I will test more complex scenes tomorrow and see if I get crashes.

    Since my CPU is nearly as fast as my GPU, I probably would change to the CPU then.



  • @bantha said in Branced vs. unbranched Pathtracing in SF:

    By the way, could someone correct "Branched" in the title?

    Done



  • I tried two more complex scenes on GPU and they failed to render with BPT. The scene I tried used three clothed V4 in an environment with difficult light condiditons.

    So yes, complex scenes won't work on the GPU with BPT right now, as it seems.



  • You need a lot of memory for BPT, and most GPU's will run out of memory in a hurry with even simple scenes depending on how many times it branches out. Even with a 32 gig GPU, you could easily run out.