Shaderlight

Specks of light when rendering interior

 
kfoojones
Total Posts: 279

Hi,

From the sequence of tests you posted, I would expect that the sky would start to become visible at an exposure of 5 if you set the Background Brightness to -3.7 (-1 from the first test minus 5 - 2.3 (the difference between the exposure setting in the first test and the third test)).

As Andrew points out, the sky is quite a lot brighter than the interior lighting in your scene (which is demonstrated with the first test – the surfaces right next to the light sources appear darker than the sky through the windows). This is physically plausible – most artificially lit surfaces are less bright than even an evening sky. Due to the limitations of computer display hardware, it isn’t possible to display the correct brightness for the sky and interior surfaces at the same time (high-end HDR displays are reducing the gap, but they aren’t in wide-spread use yet), so to get both visible at the same time, boosting the artificial light sources or reducing the sky brightness is needed. The latter could be achieved by adding a slight grey tint to the window material.

Even though those test renders were at a lower quality, the amount of speckling that is present suggests that there are still a few problems with light sources intersecting geometry. We’ve talked about the need to move skylight portals away from the window panes, but I should mention that the same applies to the other light types as well – it’s important that they don’t intersect any scene geometry, or they will be ‘randomly’ shadowed, resulting in speckled noise artefacts. Another common cause of noise is the faces themselves being ‘self-intersecting’ – this can happen if you accidentally duplicate a face or group ‘in place’, so that you actually have two faces where there should only be one. This kind of self-intersection usually results in dark ‘pepper’ noise (and also often produces moiré patterns in the SketchUp viewport), as opposed to the bright ‘salt’ noise that seems prevalent in your renders, so I would venture that the former is a more likely cause in this case, but it’s worth bearing in mind.

Regards,
Shaderlight support

blackdogsketch
Total Posts: 23
kfoojones - Mar 02, 2020 06:46pm

Hi,

From the sequence of tests you posted, I would expect that the sky would start to become visible at an exposure of 5 if you set the Background Brightness to -3.7 (-1 from the first test minus 5 - 2.3 (the difference between the exposure setting in the first test and the third test)).

As Andrew points out, the sky is quite a lot brighter than the interior lighting in your scene (which is demonstrated with the first test – the surfaces right next to the light sources appear darker than the sky through the windows). This is physically plausible – most artificially lit surfaces are less bright than even an evening sky. Due to the limitations of computer display hardware, it isn’t possible to display the correct brightness for the sky and interior surfaces at the same time (high-end HDR displays are reducing the gap, but they aren’t in wide-spread use yet), so to get both visible at the same time, boosting the artificial light sources or reducing the sky brightness is needed. The latter could be achieved by adding a slight grey tint to the window material.

Even though those test renders were at a lower quality, the amount of speckling that is present suggests that there are still a few problems with light sources intersecting geometry. We’ve talked about the need to move skylight portals away from the window panes, but I should mention that the same applies to the other light types as well – it’s important that they don’t intersect any scene geometry, or they will be ‘randomly’ shadowed, resulting in speckled noise artifacts. Another common cause of noise is the faces themselves being ‘self-intersecting’ – this can happen if you accidentally duplicate a face or group ‘in place’, so that you actually have two faces where there should only be one. This kind of self-intersection usually results in dark ‘pepper’ noise (and also often produces moiré patterns in the SketchUp viewport), as opposed to the bright ‘salt’ noise that seems prevalent in your renders, so I would venture that the former is a more likely cause in this case, but it’s worth bearing in mind.

Regards,
Shaderlight support

Thank you both for your help.
Obviously my two main ongoing issues are interior/exterior balance and the white noise.
I started reading the tutorial and I will continue to do so.
Regarding the interior/exterior balance, I understand what you’re both saying but it sounds like it’s not really possible to adjust exterior light levels with the SketchUp Physical Sky.  I was looking fo the warmer exterior light color at the end of the day from the west.  When you say that the parameter “Background Brightness” will only affect the image and not the light level…you mean the “image” of the actual sketchup model elements we can see through the windows or an actual backplate 2D image typically placed with an HDR environment?

As far as adjusting internal light levels, this becomes pretty cumbersome in a model like this, right?  There’s no table of light elements where various types can be controlled from one panel.  So each light has to be manually edited, and then test renders performed.  But if the balance between qll the elements is good…even if they are too high or low overall, exposure will take care of that, correct? 

In this case, I’d be hesitant to increase brightness of interior lights because the light spilling onto adjacent surfaces is getting close to “blowing out” a this point.  Look at the ceiling pendant lights for example, and the wall sconces on the columns.  It appears that at the end of the day I need to go to a HDR to control the exterior light levels (assuming I’m not going to cheat by adjusting the color and transparency of the glazing materiality).
As a low-budget render-guy, the main problem is that the HDRs that I have found commercially are extremely expensive.  They are priced for major commercial ad agencies and WAY out of my budget.  So I’m limited to the ones that come with SL.  Something with some “end-of-the-day” very warm light would be most appreciated as an “included” Moofe!

OK, so regarding the white noise, notice in the latest Q10 image, that the noise appears worse on certain surfaces.  The wood ceiling tiles seem fine,the wood-slat ceiling at the seating area on the right now seems fine.  But the blue wall at the rear and the green strip of the soffit on the left are really bad.  I can’t figure this out.  I have physically blocked sections of the building where there are no light portals placed, and double-checked all my light portals directions…moved them 1/16” off the glazing surface…and I’m now at a loss.  Loo at the columns and wall segments underneath the green-edge soffit on the lower left.  They appear to be mostly noise.

Any thoughts on this as to what to investigate next?  Maybe I should send a link to the model?
Thanks again very much for your help.

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awaddington
Total Posts: 390

I am a firm believer in using accurate internal light levels.  Don’t boost your interior lights for the sake of balancing with exteriors.  Design the light levels as you would for real life, use ies lighting wherever possible. Adjust the exposure or exterior lighting if you want to force the balance for artistic effect.

Side Note: A great tip I picked up from EGIE is to create a component containing your light fixture model and light source object, and copying the component instead of the lights, then you only have to change your brightness settings once for all similar light types.  Also, if you put the light source on a separate layer, you can use layer visibility like a light switch to turn lights on and off.

HDRI is still the way to go.  Remember that your model doesn’t have to be located in a volcano or on a hilltop in Spain for the Moofe and presets to be valuable.  Use the built-ins based on the light quality you want (i.e., dawn or dusk or cloudy).  Chances are you are only going to see the sky through your window.

If those do not work, there are a number of free to affordable sources for HDRI skies out there. Here are two:

—https://hdri-skies.com/
—https://www.cgskies.com/

Both links above provide free low res samples.  If this is for internal or personal projects, the nature of your scene may not need high res (I’ve attached a simple render using a very low res hdri file from cgskies)...just a light source and some action behind the windows.  And if the render is for a client with high res requirements, the high res HDRI are reasonable (US$10 to $30).

I hope this helps.

Andrew

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lowres_hdri.jpg
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blackdogsketch
Total Posts: 23
awaddington - Mar 03, 2020 04:25pm

I am a firm believer in using accurate internal light levels.  Don’t boost your interior lights for the sake of balancing with exteriors.  Design the light levels as you would for real life, use ies lighting wherever possible. Adjust the exposure or exterior lighting if you want to force the balance for artistic effect.

Side Note: A great tip I picked up from EGIE is to create a component containing your light fixture model and light source object, and copying the component instead of the lights, then you only have to change your brightness settings once for all similar light types.  Also, if you put the light source on a separate layer, you can use layer visibility like a light switch to turn lights on and off.

HDRI is still the way to go.  Remember that your model doesn’t have to be located in a volcano or on a hilltop in Spain for the Moofe and presets to be valuable.  Use the built-ins based on the light quality you want (i.e., dawn or dusk or cloudy).  Chances are you are only going to see the sky through your window.

If those do not work, there are a number of free to affordable sources for HDRI skies out there. Here are two:

—https://hdri-skies.com/
—https://www.cgskies.com/

Both links above provide free low res samples.  If this is for internal or personal projects, the nature of your scene may not need high res (I’ve attached a simple render using a very low res hdri file from cgskies)...just a light source and some action behind the windows.  And if the render is for a client with high res requirements, the high res HDRI are reasonable (US$10 to $30).

I hope this helps.

Andrew

Andrew
Excellent! 

“Side Note: A great tip I picked up from EGIE is to create a component containing your light fixture model and light source object, and copying the component instead of the lights, then you only have to change your brightness settings once for all similar light types.  Also, if you put the light source on a separate layer, you can use layer visibility like a light switch to turn lights on and off.”


Yes…I figured this out and that’s how many of the “bulk” fixtures in my models are created.

Thanks you for the tips on HDRs!  It just has seemed odd that an HDR called “Sunny Hilltop” would contain valid “data” on that scene at the end of the day/sunset.

kfoojones
Total Posts: 279

The ‘Background Brightness’ setting only affects the brightness of the ‘lighting environment’ background image or custom backplate and doesn’t affect the brightness of any SketchUp objects. It also doesn’t affect the brightness of the lighting environment’s illumination of the SketchUp objects. This allows you to set up non-physically accurate situations by independently adjusting the ‘direct’ view of the sky / outside environment and its illumination of your model. Imagine using a bright midday physical sky, or an equivalent HDR environment, and a very low Background Brightness setting – in the extreme, the lighting environment will produce a brightly-lit model but will appear very dark and look unnatural. Using a less extreme negative Background Brightness setting allows you to produce a more subtle, less unnatural balance between the two (although for true natural renders, it should be left at zero).

You should find that if you increase the intensity of all of your interior lights by the same percentage and then decrease your exposure setting by an equivalent amount (the scale is logarithmic, so it’s probably easiest to use trial-and-error to find the right amount), the interior lighting should look just the same, but the exterior will have become darker (because you’ve decreased the exposure without increasing the background brightness). In general, you can use the exposure to exactly cancel a scene-wide change in light intensity, so it shouldn’t cause any increase in overexposure near the light sources. (There’s a limit of +/-32 for the exposure setting, so you can eventually run out of room to adjust the exposure, but that would be a very extreme situation – I don’t think I’ve ever used an exposure setting anywhere near the limit!)

As you point out, changing all of your light sources can be very tedious, and as Andrew says, it’s generally a good idea to use real-world light intensities, as that makes it easier to use manufacturer’s specifications and IES files, where available, to ensure that everything is properly balanced. So that leaves the alternative of reducing the sky brightness, which you can do in one of two ways.

First, you could use the Background Brightness setting to reduce the brightness of the directly visible sky / environment. This should eliminate the overexposure of the exterior seen in your renders. The potential downside of doing only that is that the illumination of your model by the sky won’t be reduced (as discussed above), so the render will become unrealistically unbalanced. This might be the effect you want for artistic reasons, though. In the case of your renders, it doesn’t look like you’re suffering from over-illumination by the skylight (on the contrary, more sky light (combined with a reduced exposure) might help reduce the hotspots from your light sources, by increasing the light levels everywhere). To combat this downside, you can also use the portals’ Dimmer setting to reduce the amount of light that they admit into the building, thus restoring the physically-correct balance between the ‘direct’ rendering of the skylight and its illumination of SketchUp objects. (Any objects outside the portals will not be affected, of course, so if you have SketchUp objects outside the building visible in your renders, they would then become brighter than they should be.) Note that you can also use Dimmer settings above 100%, which will artificially ‘boost’ the illumination from the sky as it comes into the building without affecting its direct rendering, which might be useful to provide more ‘ambient’ illumination.

The second way to reduce the sky brightness is to use a tint on your windows. This will affect both the direct visibility of the sky / environment as well as the illumination it provides to your SketchUp objects, so it will automatically be correctly balanced. You call this ‘cheating’, but remember that is exactly what we’re trying to do! grin We want to make the exterior look darker than it really should…

Finally, what real-world photographers do, since it isn’t feasible to massively increase the light intensities or tint all the windows, is take multiple shots of the same view with different exposure settings and then combine them in a program such as Photoshop, so that the exterior parts of the image come from the low-exposure shot and the interior parts come from the high-exposure shot. You can actually do the same thing with Shaderlight if you have some HDR software to combine the renders.

In your last render, I noticed that there is an area near the right-hand side where we appear to be seeing the outside through two windows, and in that case the background is not overexposed, so there is either something different about the second window we’re looking through, or simply having two windows is enough to bring the brightness down to visible levels.

Another possibility is that the white we’re seeing through the windows is not in fact the background, which would explain why adjusting the background brightness isn’t having the expected effect. If there is any SketchUp geometry outside the windows, we’ll be seeing that instead of the background and if it’s brightly lit, it will appear white.

As for the noise, it’s quite difficult to speculate any further without being able to look around the whole model and experiment with a few things, so certainly it would be helpful if you could send a link.

Sorry this reply got so rambly… Some of the interactions of the various settings are quite subtle and difficult to describe accurately!

Regards,
Shaderlight support

blackdogsketch
Total Posts: 23

On the contrary, your language makes it much easier to understand the concepts.  You do a good job conveying technical information.. And you’re right, it is frequently challenging.

Thanks again for the excellent help.  It’s very useful.  I’m going to print all this an keep it in my Shaderlight Notebook.  I’ll send the final render. (it’s taking a while!) It is looking MUCH better.  The noise is completely gone.  The only major variable I changed was going away from Physical Sky in favor of a Moofe (in this case, the Mountain Sunrise), with the background brightness taken down by a stop and a half.  The parts of the sketchup building that we see beyond the windows are overexposed but it’s oK…it works.  The whole thing feels cohesive now.  this has been a great learning experience.  sometimes the complex projects really force the learning curve.  I have A much better understanding of the Shaderlight variables and various ways to tweak interior and exterior lighting for better balance,.  Thanks again guys!

blackdogsketch
Total Posts: 23

I’ll just follow up with one more thing.  I agree, objectively, it’s good to actually light the space as a lighting engineer would, using appropriate levels/lamping and distribution of fixtures.  Obviously its a great starting point.  However, I don’t know enough about how to adequately light the space…various ceiling heights, various fixtures and lamping options, up/downs, looking at photometrices…selecting proper IES files for fixtures, etc.  For a space like this, that would be a tremendous investment of time…for me anyway.  I’m just trying to get a “picture”, not engineer the lighting!  Most of the time these illustrations are WAY before real consultant design occurs…most frequently before there’s even a job contract!  (in this case, it’s pre-bond-vote….which is TODAY by the way…so wish me luck)

awaddington
Total Posts: 390

Absolutely true, but you don’t need engineering-level detail. Understanding the approximate amount of light that should be in the scene is good enough and saves some headaches. 

I hope your pre-bond-vote was successful yesterday.  Excited to see the final outcome.

Cheers,

Andrew

kfoojones
Total Posts: 279

I hope your render turned out well this time.

A wild guess at the noise reduction: switching from Physical Sky to an HDR environment may have changed the position of the sun (the Physical Sky uses the sun position determined by the location and date / time in SketchUp whereas the HDR environments have the sun position baked in), which might mean the noisy surfaces were no longer receiving direct sunlight. Direct sunlight can produce noise (especially in the presence of complex shadow casting) because the difference in illuminance between the sun and the diffuse skylight is very high. There didn’t seem to be particularly strong shadows obviously coming from the sun, though, so that explanation isn’t totally convincing…

Regards,
Shaderlight support

blackdogsketch
Total Posts: 23
awaddington - Mar 04, 2020 03:45pm

Absolutely true, but you don’t need engineering-level detail. Understanding the approximate amount of light that should be in the scene is good enough and saves some headaches. 

I hope your pre-bond-vote was successful yesterday.  Excited to see the final outcome.

Cheers,

Andrew

Final render attached.  Pretty satisfied.  Needs a few tweaks but overall very good I think.  Bond vote failed.  So, this is all going to be a pretty picture and nothing more.

Image Attachments
SBMSHS_DIN_COM_03-FINAL_RENDER_HD_Q10-DOWNSIZED.jpg
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blackdogsketch
Total Posts: 23

The learning continues ...in more ways than one.
Let’s talk about HDRs!
The HDR contains the embedded light quality and time-of-day from the original scene.  it imparts that light quality on the model….and we can adjust “Background Brightness”.  but this does not adjust the light level falling on the model (as you have previously stated).

So is there any way to get the light level actually falling on the model adjusted?  Or do you just have to get a different HDR?

awaddington
Total Posts: 390

Thanks for sharing the final render.  Sorry to hear about the bond vote.

Re: HDRI I think it is static, you would have to increase the interior light then adjust exposure.

blackdogsketch
Total Posts: 23

Here’s another question.  Some HDR packs contain an HDR file, and some very high rez jpeg files.  The jpegs seem to behave in the same way as the HDR file…you can rotate and move around and see it in “3D”....when would you load an HDR and when would you load one of the high rez jpegs. The jpegs seem to contain the light quality too as it’s casting similar soft shadows on my model.

awaddington
Total Posts: 390

Technically, you can use bitmaps in place of the HDRi.  I made an image in a graphics program consisting of a midnight blue background and a pale gray circle to simulate the moonlight once.  It wasn’t great, but it worked with some fiddling - the HDRI is a better way to go.

The HDRi files have a lot more data in them and because of the high dynamic range, you can adjust your exposure without losing details in the image as quickly. There is more to the HDRi than that.  I won’t pretend to be an expert.  Shaderlight support may add some texture to that discussion.

The jpegs may not be intended to replace the HDRI but to augment it.  Even the presets and Moofe lighting environments in SHaderlight have accompanying jpegs available.  These are found on this site under resources->lighting images.

When using the HDRi setting, you may use the images as background images. The images match the location and time of day of the HDRi. They are not used to generate light, they just provide a higher quality version of what you would see from the HDRi when looking out the window.

Andrew

blackdogsketch
Total Posts: 23

Andrew.  I’m still a bit confused (as usual).
Shaderlight has one “spot” to load in a background.  We can load in an HDR, or a jpeg.  The HDR contains the range of exposure and other data…so when would you ever opt to use the jpeg instead of the HDR?  You’d lose the value of the embedded HDR data if you simply use a jpeg.

Also, the high rez jpegs supplied in the HDR “packs” seem to be viewed in Shaderlight the same as HDRs.  That is, you can pan around, look up and down, and see the whole sky/scene.  Unlike a regular jpeg (or what is called a backplate in rendering terminology) which is flat…and when yuo pan or chage the rotation of the jpeg, yo use the seam between left and righ edge of the image.

So what makes those included “special” jpegs behave differently than a normal “flat” jpeg?