IRAY: iteration # vs time

Scavenger

What causes an interation's length to..render? 

Is it size of area? number of stuff in the scene? Something else?

 

I had a long running render last night..after 4 hours, it's iterations were in the 500 range (with about 80% convergence).Convergence is convergence, but i'd have thought the iteration count would be higher at that point.

mjc1016

I'm not sure there is a single factor...an iteration is one complete time through the render, so yeah, size plays a role, but so does what is in it, what the lighting is and even what the surfaces are.  There are probably more items that go into it, but you get the idea.

And how long it takes to get through all of that before it starts over again...

Testing6790

In a fast and lose way, the "quality" of the render slows down iterations. Many things make up quality, as we all know. The main things I've noticed, with my limited knowledge, is the ray length, the image dimensions, texture quality, the literal "render quality" dial, and shader details. Reflectivity is killer.

There is definitely something else that I'm as of yet unaware of, though. I think I get close to 1000 iterations and 10% convergance after 20 minutes in my current scene.

TangoAlpha

Is there a way to increase max iterations beyond 15000? I have a scene that stops at 15000 iterations after 2 days (cpu render) and is still only at 30% convergence. (it's a dim interior scene using Sicleyield's dust rays technique)

Steven-V

Iterations definitely do not occur at a constant rate. Nor do all scenes require the same # of iterations.

Factors that affect render time (it seems to me, but I have not tested rigorously) are:

1. The TYPE of light. Speed seems to be, fastest to slowest, HDRI < Sun/Sky < Mesh. I have not tested much with spot lights yet.

2. The NUMBER of lights. Two mesh lights in a scene make it take longer than one, all other things being equal. But the increase in time is non-linear and not easily predictable.

3. The BRIGHTNESS of the total light in the scene, This is why I said "all things being equal" above. If the 2nd mesh light makes the scene brighter, it could balance out the extra computations that a second light source requires.

4. The number of POLYGONS in a scene. A cube in a blank space will render faster than Victoria 7 in full high-def clothing.

5. Displacement subdivisions - this is the #1 render killer. If you have a displacement map and had to subD it, you are going to get toasted on render times. If possible change 'em to bump maps.

6. Render image size. A 2000x2000 image will take longer than a 100x100 image to render. Again the increase does not seem to be strictly linear. Probably follows the invers square law or something -- i.e. cutting the image in half size will cut the render time in a quarter or something.

Richard Haseltine

Tim_A said:

Is there a way to increase max iterations beyond 15000? I have a scene that stops at 15000 iterations after 2 days (cpu render) and is still only at 30% convergence. (it's a dim interior scene using Sicleyield's dust rays technique)

 Click the gear on the slider, Parameter Settings, adjust the limit or turn Use Limits off in the dialogue.

TangoAlpha

Richard Haseltine said:

Tim_A said:

Is there a way to increase max iterations beyond 15000? I have a scene that stops at 15000 iterations after 2 days (cpu render) and is still only at 30% convergence. (it's a dim interior scene using Sicleyield's dust rays technique)

 Click the gear on the slider, Parameter Settings, adjust the limit or turn Use Limits off in the dialogue.

Ah, thank you. It's simple when you know! :) 

Testing6790

Tim_A said:

Richard Haseltine said:

Tim_A said:

Is there a way to increase max iterations beyond 15000? I have a scene that stops at 15000 iterations after 2 days (cpu render) and is still only at 30% convergence. (it's a dim interior scene using Sicleyield's dust rays technique)

 Click the gear on the slider, Parameter Settings, adjust the limit or turn Use Limits off in the dialogue.

Ah, thank you. It's simple when you know! :) 

This works for almost all parameters. When I create a custom figure the first thing I do is set the limits of the eys up/down and side/side to -2 to 2 instead of -1 and 1, for more movement. 

Oso3D

Yeah, I was trying to make art quality renders at 9000 x 13500, and realized there is a 10000 pixel cap on renders (which can be shut off in parameters).

 

Oddly, it seems that shutting off that limit isn't saved, so every time I'd open the file I'd have to shut off the limit and change the dimensions.

sandmanmax

OK - i'm confused.  I know how to turn limits off but in this case, what am I turning them off on in order to increase the iterations?  And I'm not seeing where to set it.

L'Adair

sandman_max said:

OK - i'm confused.  I know how to turn limits off but in this case, what am I turning them off on in order to increase the iterations?  And I'm not seeing where to set it.

To turn limits off to increase iterations:

• Go to Render Settings
• Click on Progressive Rendering
• Find the Max Samples parameter
• Click on the gear icon
• Select Parameter Settings from the drop-down menu
• Click on the checkbox for Use Limits
• Click on the Accept button

 

sandmanmax

Thanks - that's what I needed!