Render times & are they normal?

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Render times & are they normal?

Post by wro » Sat Sep 24, 2016 11:44 pm

Hi guys, I really hope someone can help me or would take their precious time to explain me, what to do.

Here goes, after experimenting some time with Kerkythea I found it is getting me nowhere fr one reason: my rendering times are waaaay too long. Twilight gave me quite much faster results and helped me a lot in wrapping my mind around lighting and materials, but complicated scenes still set my limit right now. Hell, even quite simple scenes give me the waiting hell.

Now here is my model, that I just took for getting a feeling for modelling and materials. Nothing fancy, there are not quite 10k faces in it and around 30k lines. There are Three light sources, sun is off, and thewhole scene is packed into a box (right now, for bumping around the photons). I have exactly 2 spot lights (diode is one, another just from the top on the model), and, granted, one emitter rectangle (which sums up to two emitter polygons i guess (that is the light on the meters).

Now the render time for the image I am attatching is approx. 5,5h in interior+ settings with only 24 passes, which, to me, seems high (granted, the resolution is set to 2400x1000). I have the same issue in Kerkythea, but can't get any help on that forum for days now, so I switched to Twilight while waiting...

Now my machine is not the youngest, but it still gives me Xeon W3530 Quad Core Prozessor @ 2,8 GHz (4x Core / 8x Threads) with 8 MB L2, EM64T, HT, VT, supported by 12 GB DDR3 RAM on 64bit Windows.

I am reading about ppl, who render on laptops with dual core and get their results in minutes. What am I missing??

The image it produced in that 5.5 hrs:


Please please please help me deal with that, or direct me, what hardware do I need to handle that. My other scene which i am looking to play with is 700k faces and around 10x the amount of light sources with sun on - needless to say I was only able to render that in useless sizes like 500x200 or sth and it also took several hours to get to 50 pass or so.

Can anything be done? Sorry for being lame on that, I just really am out of ideas now.
kenwood_point_lights_plus_reflect_object.jpg (288.71 KiB) Viewed 4447 times
Last edited by wro on Sun Sep 25, 2016 4:44 pm, edited 1 time in total.

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Re: Render times & are they normal?

Post by Chris » Sun Sep 25, 2016 1:42 pm

What render preset are you using? I assume that since you are talking about passes, it's probably one of the Interior presets? Edit: Oh, I see you wrote that you are using Interior+

Its tough to know what the issue is without looking at the scene itself, but 5.5 hrs for rendering a single object in a room definitely seems very high.

Some possibilities:
  • Big texture sizes. A lot of models available for download have ridiculous enormous textures. While it's tempting to go big, you are killing your render time. Usually we can go much smaller than we think, even down to 128 or 256 pixel images.
  • Lights intersecting geometry. Be careful of your light radius and make sure it isn't colliding with geometry. Remember that the light radius only affects the softness of shadows, it isn't needed to make the light brighter.
  • Certain materials are time consuming. Metal and Brushed metal, SSS, translucent, and some others tend to be slow to render.
  • You put your light behind glass. In the effort to model a realistic light, sometimes people put lights behind glass or a translucent surface. This will absolutely kill render times. You should never do this unless you are modeling and rendering a product shot of a light fixture itself.
  • Insufficient light. If you are using the Interior presets, there isn't really a limitation on the number of lights. So your render will actually go faster if you have more light (which is pretty much true across the board; dark scenes are slow).
Hopefully something in there helps. I suspect the issue is related to how you have placed your lights, rather than the number of lights.

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Re: Render times & are they normal?

Post by wro » Sun Sep 25, 2016 4:33 pm

Thank You Chris for an answer! That first.

Well first off I know the model well since I built it from scratch. I assume there is noithing wrong with it (well not too much ;)), I even used 12-section circles foolishlyXD

Indeed there is one large or very large texture in this one, but only one - that is the front, to be exact the typing on a transparent PNG. BUT, that slowed my render only around 8-10% since I have done some others before I taped this huge piece of texture on it - this is deniable (?).

Well indeed the lights behind the VU-Meter glass are well... behind that glass. These are also the LES instead of point or spots. So you would suggest removing the glass front, am I correct?

Same goes for the diode - i tried two ways - with a fake emitter halfsphere and spotlight before it, then also with a translucent plastic half-sphere and the spot light in it - that would intersect geometry. There was no significant change on that neither with the Raytracing nor with some of the biased methods (I don't use them, since I NEVER get any results for preview in a reasonable time).

I will try to render that with some diffrent materials, since virtually ALL the faces are brushed metal and aluminium in this one - mostly with procedurals or small textures. Suggestions which I should take instead just to compare how much time would that save me? I assume that woiuld be the right way to troubleshoot instead of comparing between diffrent models.

On the Insufficient light - My topdown spotlight gives 20k lumen. The dimensions are in a cube around 5m x 5m x 5m, because I put the model in a scale of 10:1 to not have issues with halves of milimeters while measuring (which I would have had if I put it on a scale 1:1 or smaller). Is that not enough in these dimensions? I assumed that a box of (0,5m)^3 would be well lit with one standard bulb around 400 lumen, after judging the 10:1 scale and considering the square falloff i ended up with sth. around 20k lumen. What luminance would be then sufficient for this cube ((5m)^3, two objects in it (i had to give the brushed metal something to reflect ofc, so there is a simnple bookshelf in front of the amp which cannot be seen in the scene).

BTW.: Is there a diffrence in times when I angle the camera diffrently? Common sense and as far as I understand the basic of how rendering works tell me yes, but what do I know in the end XD

Btw. thanks for clearing out my question if the sizes of the Light sources matter - I was just reading on that.

So, could you pls put a number on that, if it's possible? How long SHOULD it take on my machine to render that in Interior/ Interior + in say..100 passes around 1600x800 on my machine?

I assume, that I should not need more than an hour is that correct?

Could you maybe direct me to a correct built scene (preferrably with some reference render times), that I could just download and fire up just to determine if it's the settings of my model or the hardware/system settings?

Again, to clarify: These long rendering times not only happen on especially THIS model... I get them all along with more complicated models as well... I havent been trying to render a simple cube or sth. tbh. because I have no reference whatsoever and I guess nothing really relevant has less than 10k Faces anyway...

I know I am asking a lot of you guys and I am really very helpful for your precious help. I just figure I ran out of options to figure it out on my own and I am really frustrated not being able to learn from own renderings and playing with settings (resolutions of 300x150 can only take you this far XD)

Again, thanks, thanks, thanks!

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Re: Render times & are they normal?

Post by Fletch » Mon Sep 26, 2016 8:29 am

Easy 10 (BiPT+MLT) is the slowest rendering process. (It's simultaneously the most powerful.)

Rendering anything at 2400px on Easy 10 is going to take a long time unless you have a super computer.
This is because it's an overlay of two different unbiased algorithms.

Easy 10 (Bipt/MLT in Kerkythea) is intended for rendering things like lasers being split through prisms. So it's a very powerful setting, and is there for people who love to get super technical. It is not however a good choice for rendering simple scenes like a stereo receiver... or pretty much anything... unless you don't care about render times.

Easy 10 splitting light: Subject: Splitting a Beam of Light with a Prism
or Easy 10 can render jewels: Subject: Gemstone Jewel Diamond Wine Glass and Spoon by Massimo

Avoid these mistakes when getting started:
  1. Rendering preliminary renderings with final render quality settings,
  2. Rendering a high resolution rendering for preliminary test renderings
Use Easy 09 (MLT) it will clear up in less than half the time as Easy 10, and look great in almost all cases.

However, if you want VERY fast rendering results that look great - setting your light emitting surfaces to fake, and lighting your scene withHDR Light Tent images, then rendering with Easy 06, you may be surprised at the results and how fast you get them.

Finally, render at 800x600 (or similar size) while testing things - a professional workflow is to start small and work your way up to the final.

Subject: Pentax Camera - great model in Google 3DWarehouse

Subject: studio lighting, interior lighting
Fletch wrote:The go-to place for tips and tricks is the Tips and Tricks section.

There are 2 master lists of the top tips and tricks -
Most tips and tricks for Twilight Render V1 also work for V2, although the look of the interface may have changed slightly.
Subject: Best Of Tips and Tricks - The Master List - V1.x
Subject: Best Of Tips and Tricks - The Master List - V2.x

The 2 best threads for learning studio lighting in Twilight Render are here:
1 Best thread ever about product shots/studio shots on Twilight's forum. Includes links to HDR and studios and test files, everything.
2 Jewelry and Product Shots - the Right Light a.k.a. "photo studio" "lighting studio"

But don't miss the Freebies section of the forum, where you can find 3 ready-made studio backdrops for SketchUp.
Subject: Studio for product shots

Also see this thread is about Light Temperature and Color
Subject: Fender Stratocaster
Fletch wrote:Reflections are of utmost importance when rendering a product like this.
Be sure you study this thread about photography studio shots.
If the screen is too close to your product, the metal (chrome) will reflect the white background studio screen and not give you the look you desire. But if you think about the problem as you would in the real world - "Hmm... how can I get the lighting I want but the reflections I want?" I think you will come up with a good setup.

3 great different studio scenes you can download and learn from immediately.
Subject: Pentax Camera - great model in Google 3DWarehouse
Subject: Magnifying Glass Scene
Subject: Gemstone Jewel Diamond Wine Glass and Spoon by Massimo

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Re: Render times & are they normal?

Post by wro » Mon Sep 26, 2016 1:56 pm

Thank You, Fletch, for taking your valuable time directing me to those ready made scenes - I will look to them the next days - I was lloking to your directions before, but more in the theoretical parts. Directing me to correctly models is a huge help!

Of course I was trying to go lower and testing diffrent settings, I would also never use the high res for preliminary. Basically the problem seems to be though, that it really does not speed anything up at all in my case. Doing Low+ (03) seems to take at least the same amount of time that anticipated 30-40 passes of unbiased would take (for low lightsources count <5), say 09/11 for everything above 400x400, which is, for preview's sake counterproductive, since I seem to get a good grasp of how it would look like around the 20th pass...

That is what bothers me. If I have 10-15 or more lights, ok, but...?

To tell you guys the truth I took the advice of Chris and double checked the intersecting of lights vs. faces etc., which, granted, has not changed much. BUT then I started just a whole new model giving extra care, got to 2,5k faces and gave it around 20 lights up until now, and I have to admit, render times are just a fraction of what I had above (results in 10-15 minutes in Res > 720p). What bothers me, the amp is not the only model I worked with, and I seem to be doing something in the process, that breaks my models since they all start to take insanely long to take in the process. I intend to find out, what it is, using your guys' outlined advice (though I was convinced, that I am not making any grave mistake on the basic stuff you both mention, seems like I am).

Thank you so much for the help, I will report what killed the render times as soon as I know, but it seems, that it is my mistake, just have to check which issue adressed by you guys it is...

Very special thanks for the hint with the light tent - I can't say I wa looking for sth. like it, but I intended to, and now, thanks to you, I don't need to anymore!

Thank you!

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Re: Render times & are they normal?

Post by Fletch » Mon Sep 26, 2016 6:30 pm

My guess is that you have accidentally applied a light emitting surface to a curved object. That is what would drastically increase rendering times.
Twilight has a diagnostic function.

The only other major modeling problem we regularly see is with many nested components or groups. Nested groups and components should not exceed 5 or 6.

Subject: Diagnostic Report #Diagnostic #report #log
Fletch wrote:Any rendering has the potential for something to go wrong. In our vast experience, it's usually a material, but often we have seen a "quirky model" downloaded from the 3D Warehouse as the culprit when a render fails. If you suspect it's a quirky model, simply exploding the model has often done the trick- often a problem model simply has too many nested groups and components. Exploding a Group that contains a group of groups and components, without exploding the individual components will often solve the problem.

If your rendering is still failing, and it's not due to some "quirky" 3D Warehouse model, then it's likely that your computer is running out of RAM.
If you are running out of RAM, it's likely due to one of two things - one or more textures in the model are of too high resolution, or there are too many lights.

There are two tools we developed for helping to pin-point problem spots in your scene. The Log File, and the Diagnostic Report tool.

For the Diagnostic Report dialog, go to Plugins>Twilight V2>Diagnostic Report.
Then choose either "All" or "Materials" for the type of Diagnostic Report you would like to receive.

For the Log File, start the log file before you render, then see what is written in the log file as you experience the problem while rendering.
to open the Log File, choose to do so in the Twilight V2 Options Dialog. For the Options Dialog, go to Plugins>Twilight V2>Options.

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Re: Render times & are they normal?

Post by wro » Mon Sep 26, 2016 10:13 pm


For sure it's not the light emitter on a curve - I take great care not to do that, since that is the issue lots of users have/had also with kerkythea.

Tbh. I don't know if the nested groups could be the problem. Might, since I have not known about the "5 nested objects" rule yet.

There are some things to check and I will use the diagnostics. Ofc. I will report what I found for anybody, who might run into simmilar trouble. This will take me a few days though, stupidly enough I am kinda occupied this week.

Thank you so much for your precious time, hope I can recontribute to community any time soon :)

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Re: Render times & are they normal?

Post by Fletch » Tue Sep 27, 2016 1:33 pm

wro wrote:... since I have not known about the "5 nested objects" rule yet.
less of a rule, and more of a guideline, I'd say keep it to 7 or lower. I've seen 10-15 deep group/component nesting before. Components nested 15 deep is simply too much.

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Re: Render times & are they normal?

Post by wro » Tue Sep 27, 2016 1:41 pm

Probably also not really needed given a sleek working habit. I doubt that I exceed 7, but I have not given it any attention in this aspect. Managing so many lvls would be cumbersome somehow :)

I will look into that as soon as I get back home.

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Re: Render times & are they normal?

Post by wro » Tue Oct 11, 2016 9:08 pm

Hello guys, sorry for not having updated you for so long.

Though you might not really need the final thought, since you are the experts, maybe someone will benefit of all the hints you gave me.

First off, it only took me so long, since I was checking every single model I was experiencing trouble with under any aspects of what you guys pointed me to.

Turns out, there seems to not be anything wrong with my system after all - I seemed to underestimate the importance of some of those rules. In my particular case the most relief was given by using less metal and brushed metal materials, especially on the complex surfaces. Removing those on very small parts (like door knobs seen from afar) and replacing with fake metal textures gave me the most boost (around 30%, but I was not measuring).

Obviously this would not work for the amplifier, which basically is composed of brushed and galvanized metals and I haven't managed to speed that up substantially. I ended up making the model smaller, since I built it in a 100:1 scale (thinking the scale would not change anything was obviously a huge mistake for whatever the reason) - that made it a little faster, when not really much (10-15%). Don't know if i am maybe biased about it.

On some other models removing too many Lights intersections with surfaces helped somewhat a lot (I reported about it before).

Concluding, I hope some people that run in this sort of trouble might benefit from the thread the way I have. To those guys - double and triple check all those issues, since for me at least, it turned out to not really work linearly. What I mean is: The slower rendering times would not simply add up, but factor in a way that is a little more complicated. Foolishly I was calculating somehow like: a scene takes 10 minutes to render without special materials, then 15 minutes with translucent, but without metals and then again 12 minutes with metals but without translucent. So I thought, that if I add both translucent and metals, I should be done in under 20 minutes (all those times are just exeplary, same with materials) - not really, combining problematic materials turns out to add more rendering time than just those materials on their own need leading me into thinking something is broken.

Just like I posted above, and that's an example: The large texture on its own was not a problem when tested, also not really after adding some metals. But then, adding even a single light all together seemed like slowing down the render as a whole. The texture without any lights apart from the sun ment 15% longer render, but with metals added, removing it gave me 25% less render times.

After analysing all of this I came to understand better, how this stuff interconnects and was able to speed up the overall performance or at least better anticipate the time needed.

Not thinking I know it all now, nevertheless thank you Chris and Fletch for putting the possible soultions together for me in this topic, it was not laziness, just a lack of understanding - I missed it completely.

I hope I don't have to bug you too much any time soon, I remain thankful and looking forward to buying Twilight (and giving another shot at Kerkythea) :)

Would love to finally make some worthy renders to show off, but this will take some (a lot) more learning I guess

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