Resume / distribute an interior progressive rendering

[Ecuadorian]

I have already posted this trick in the Kerkythea forum, but in case you haven't seen it, here it goes. This works well with presets Easy 09 and Easy 10.

"Resuming" a stopped interior render

If for whatever reason (have to restart OS, need to cool down your PC, or simply need 100% of your CPU performance back for a while) you need to completely stop your progressive render, what you already have cooked is not completely lost. Just do this:

1 Before stopping your render, write down the number of passes already done. After stopping, save it with a filename that includes the number of passes.

2 When you're ready to continue rendering, add one pixel to the width of the rendered image. When stopping it, follow the process of step 1.

3 Now, in your calculator, divide the number of passes of the second image by the total sum of passes and multiply by 100. Write down this number.

4 Open the first render in your image editing program.

5 Paste the second render as a layer on top of the first one, and assign the number you calculated in step 3 as the layer opacity.

Now you have an image as clean as if you had rendered the total sum of passes in a single session.

Distributing your progressive render between two computers:

Set it to render simultaneously on two machines but add one pixel to the width of the image on one of them. This will be your “second render”. The rest is the same.

Note: when it says “raytracing N/10000” it means it has already done N-1 passes, so the number you have to write down is actually one less than the one displayed.

An actual example:

A render stopped after completing 3 passes. Size: 640x459

3-passes.jpg (268.4 KiB) Viewed 18804 times

A second one stopped after completing 2 passes. Size: 641x460

2-passes.jpg (280.27 KiB) Viewed 18808 times

After layering the second one with opacity 40% (2/(3+2)*100), we have the equivalent, in terms of "noisiness", of a 5-pass render:

stacked.jpg (116.14 KiB) Viewed 18797 times

[Ecuadorian]

A real 5-pass render of the same scene for comparison:

5-passes.jpg

The difference between the real 5-pass one and the stacked one:

difference.jpg

As you can see, brightness remains unchanged, but noise distribution (concentrated in the darkest parts) is slightly different. With more passes this difference will tend to zero. The faint lines are the difference caused by adding a pixel to the second render.

The original Kerkythea.net thread for those curious about the need for the tiny change in image size between successive renders:
http://www.kerkythea.net/phpBB2/viewtop ... sc&start=0

[Fletch]

Nice tip, Miguel, thanks.

[derei]

Hmm, this is nice. I did not understood all yet, I will read again. But I have one question for now:
Why do I have to add one pixel to the total width of the image? I would like this step explained better. This trick is about to save my day... or to ruin it

[derei]

Hmm, this is nice. I did not understood all yet, I will read again. But I have one question for now:
Why do I have to add one pixel to the total width of the image? I would like this step explained better. This trick is about to save my day... or to ruin it

Sorry, doesn't matter. I just skipped the part with

The original Kerkythea.net thread for those curious about the need for the tiny change in image size between successive renders:
http://www.kerkythea.net/phpBB2/viewtop ... sc&start=0

I read now and I understand. Maybe the TW team will spend some time to make a real stop and resume feature (I'm guessing that is applicable only to progressive)

[derei]

Anyone tried this with spherical render? As changing the size doesn't affect rendered area (the entire scene will be captured on frame), I think that will appear some stripes on final image, but I haven't tested it.
Any opinions ?

[Fletch]

well, you change slightly the resolution of the image, render, when ready you stop the image, then you RESIZE that image to be identical to the orignal rendering. So, no, there theoretically should be no reason it wouldn't work just as it does with a normal camera.

If resume render were supported by the engine, resume render would already be integrated.

[Ecuadorian]

Any tiny change should work to change the "random seed" used to render. Even changing the RGB color of a material from 180,63,54 to 180,63,53.

BTW, you can also use the pause button in Twilight. Pause, save, send that noisy image to your impatient client, and then click the pause button again to resume rendering if he approves it.

[derei]

Any tiny change should work to change the "random seed" used to render. Even changing the RGB color of a material from 180,63,54 to 180,63,53.

Wow, so is not just the size? That's cool! A very small change of color will pass unnoticed especially if it's a object that is not very obvious in scene.
Thanks a lot!

[bizmen]

BTW, you can also use the pause button in Twilight. Pause, save, send that noisy image to your impatient client, and then click the pause button again to resume rendering if he approves it.

this feature is pretty cool, I remember hitting the print screen button to capture the image of the screen then edit with PS before sending it to the client for approval. The best feature for TW and KT users.