Branched Path Tracing

Hi, I’m trying to learn the BPT but there are some things you do not understand

  1. why worsens the appearance of rendering increasing the samples ?

I’ll add the link

  1. is there a direct illumination problem?
  2. besides using all samples with a value of 1, how do I fix that problem?
  3. BTP is still not ready project or are already mature as the PT?
    can I use it in production?
  4. Do you know of any good tutorials? I have found very little on the net


  1. I’m not able to reproduce the problem with the attached file. Are you using CPU or GPU?

  2. The light path thing on the sun lamp is rather odd, but I think it should be ok? I would consider disabling MIS with the sky texture, or at least lowering the sample count to 1-2.

  3. Again, I can’t reproduce the issue and I’ve never seen it in my own scenes.

  4. I hardly ever use regular PT for anything. BPT is much more efficient on most scenes once you learn how to use it. FYI, Arnold’s only render mode is essentially BPT, there is no regular PT mode like Cycles has. I have never seen this widely complained about, and I wouldn’t use it if they added it. I recommend using the “square samples” option with branched path for simplicity’s sake.

  5. There’s an older tutorial from Blender Cookie that is pretty thorough:
    Speaking of Arnold renderer, while this guide is written for it, the concepts pretty much apply the same to Cycles, as BPT is loosely based on Arnold’s integrator:

BTW, I wouldn’t use 14 for the AA sample level unless you have a specific reason to do so. (ie, depth of field noise, GPU timing out, etc). Try starting with AA=4, and adjust the subsample levels from there. If you have a lot of sample objects, or motion blur, or DOF, you might need to raise AA samples to something like 6-8, or maybe higher. Also, if you are using GPU, excessive subsample levels can cause the some OS to kill the driver/app for taking too long to respond, so lowering them and increasing AA to compensate can workaround that.

  1. I am using GPU (GTX 580-3gb). Using the CPU the problem goes away!
    Perhaps this will be a bug? I hope there is someone who tries some other gpu maybe newer than my!

  2. what is a node copied from somewhere but I do not remember where

  3. Using the CPU the problem goes away!

  4. ok, tnx

  5. I know these tutorials but I have not been at all useful

thanks J_the_Ninja for all the other tips.
I will take even those

Hi, this is a bug.
I make report >
I hope it will fixed for Blender 2.77

Cheers, mib

ohhh tnx very much man!!! :slight_smile:

Yep, that was indeed a bug in the light falloff node in combination with a sunlamp. It should be fixed in the next nightly builds (and 2.77).
Thanks for mentioning and providing the file!

In case anyone cares, the fix is here:

tnx @lukasstockner97