How to speed up render time

[gospodinf]

I'm interested in fast rendering, sketchup 2015 plugin.
I use it as a design tool for interior design so i need it to be around 5 min.
I use Easy 03, 800x400, the quality is good enough for my clients (they say "wow it looks real" . When i want a really really good render i pay someone.
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I see that when i put a lot of stuff in models it slows down to 10-15min, but i cant figure out what is the main reason, so i would like some guidelines.
1 - What kind of light is the fastest? (i always use rectangular emitter surfaces, is that the fastest? false emitters - do that add a lot time to render even thought they dont project light?)
2 - Do textures slow down the render? (i can put lower res textures if that is the case)
3 - How much does complex geometry slow it down? (rounded surfaces, revolved surfaces etc. should i reduce number of sides on circles before extruding?)
4 - How much do "special surfaces" add to the time of render - mirros, arch.glass, thin curtain, gloss paint? (which one of those is the worst?)
5 - Do translucent surafaces from sketchup templates slow it down a bit - lets compare a white surface to a white 50% transparent? (i ususally put transparent chairs or vases in the first stages of design draft)
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I plan to use these guidelines to make my own componenets (newspapers, coffee machines, vases etc. for interior decoration) because warehouse componenets are not that optimised.
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Thanks in advance for your feedback, i have been thinking about this problem for some ti me now!

[Chris]

Basically everything you listed slows renders down.

The one thing I can say absolutely is do not use light emitting materials with Low/Low+ through High/High+ (the biased settings) unless you are absolutely sure of what you are doing. 'Fake' Emitters are ok, however.
Otherwise, I can't put a specific number next to any of the characteristics you listed, but all of them affect render times. Reducing them will improve render time.

1. What is the fastest light? Spot light because it targets light to where it needs to go. Light emitting surfaces are probably the slowest (but is somewhat scene dependent).
2. Large textures do slow renders down but probably not the biggest culprit. They will eat up memory however. It's always best to keep them to the absolute minimum size whenever possible.
3. More geometry, slower render, no matter what. And this includes geometry that isn't even visible in the scene so hiding invisible geometry will always help.
4. "Special" surface will slow renders down a lot. But it is entirely dependent on the type. Mirrors will have very little impact. Subsurface Scattering, very high.
5. There is a difference between transparent and translucent. Both will render slower than a flat opaque, but translucent will render slower than transparent. And translucent with scattering (subsurface scattering) will render very slow. Most of the good curtain materials are of this type and will render slowly.

[Fletch]

Shiny materials render more quickly than rough or blurry reflections. So, blurry metal will render more slowly than shiny metal.
Reduce all textures to be less than 1000px wide. Larger textures can have a major impact on render times.
Set all emitting surfaces to be FAKE emit - they will add NO render time at all. But if you accidentally forget one, and it actually is emitting light it will increase render times.

Subject: Color of Lights / Light Render Speed Comparison

[gospodinf]

great info!

what do you think is fastest for simulating daylight coming through window:
1 - make the glass an emitter surface towards inside (i usually do that, i see now this slows the render down)
2 - sky portal
3 - make the window transparent and just let the daylight in
(i dont need the view through the window)

[Fletch]

If no need to see out, set spot light shining through window for fastest rendering with Easy render settings 1-7... turn off sun to avoid double shadows from sun and extra spot light. place spot light outside of window but at least 3m away so that spot covers entire opening. The spot light is fastest because nearly all of the photons traced from the light source are entering the window aperture. With the sun, few photons actually enter the window aperture.
Use Architectural (thin) glass - not "realistic" glass for your windows.

If rendering with Easy 9 - interior render setting - set glass to be light emitter as you said. Or set invisible light emitting plane just outside of window if you need to see out of the window. - this is what I did in the attached 2 renderings. I don't go for speed - but for looks... so I render interiors with Easy 09. It saves time in the end because I don't worry about lights or materials, I use what is best, no fussing with optimizing everything. Then let the computer figure it out with a bit longer render times. I Denoise with Topaz Denoise 5 plugin for photoshop if needed.

[rudy970]

Thought I would jump into this thread instead of starting one of my own.

I have a night scene that I am trying to render (interior lights shining through glass and translucent surfaces) at dusk (very late sun settings). It is taking FOREVER. I do have it set up for a large image 2000x1500 and #4-7. I have a Core i7 processor.

What other options do I have? Are there render farms or services that I can use? It takes so long even on low settings that I can't easily tweak the lights to get the scene worked out.

Thanks!

Rudy

[masloprojekt]

I wonder whether if I select elements of the model shown in a scene and then I set to render only the currently selected this will speed up rendering time? Or this option works only like hiding other elements so still all geometry is processed ? If "render the current selection only" really speeds up rendering time maybe You should consider adding some selection manager to batch render.

[Chris]

I wonder whether if I select elements of the model shown in a scene and then I set to render only the currently selected this will speed up rendering time? Or this option works only like hiding other elements so still all geometry is processed ? If "render the current selection only" really speeds up rendering time maybe You should consider adding some selection manager to batch render.

This would more appropriately be handled by hiding geometry using your SketchUp scenes. And yes, hiding geometry can make a very big difference in render times. Say you have an entire house and you are only rendering the bedroom, hiding the rest of the house can make a huge difference.

[Fletch]

@Rudy - my guess is that you have illuminated something someplace in your scene using Light Emitting Material template. If so, it will cause your scene to take a long time to render. Pro users can use the Plugins>TwilightV2>Diagnostic Report to show which materials in your scene have which template applied - there you will quickly see if you have accidentally applied a light emitter to any surfaces. Light Emitters take a very long time to render on Easy 1-8 render settings. Set the template to "Fake Emit" and it will take no time at all to render them, but they will not emit light, only they will "look" like they are emitting light - this is very useful if you want to quickly fake a lampshade. Be sure to UNCHECK the "Cast Shadows" option for Fake Emitting materials, so they will not block the light inside the lamp - if this is the case.

If you have high resolution textures, reducing the texture resolution can speed up rendering. All Material Texture resolutions are listed as well in the Diagnostic Report so that you can quickly see the sizes. (Diagnostic>Materials)

Putting geometry that will not be scene in your scene, or in the scene's reflections, and then turning off this layer for your rendering scene will definitely save render time and scene processing time.

[masloprojekt]

This would more appropriately be handled by hiding geometry using your SketchUp scenes. And yes, hiding geometry can make a very big difference in render times. Say you have an entire house and you are only rendering the bedroom, hiding the rest of the house can make a huge difference.

...so i had to misunderstood sth. Now it is clear. But still using render the current selection only work as hiding the rest of the model ? There are some neat selection managers out there, which i'm using.