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How Many Passes Do You Need?

 

Let's take a look at what to expect from running a high number of passes and how to determine when enough is enough. Assuming one has the lighting and materials reasonably configured there is in most cases no significant gain in running 100's of passes for hours on end. After a few passes you will likely see your trace at about 80-90% of it's ultimate quality, if not then your lighting or materials are the root cause and running significantly more passes is not likely to improve things by much.

 

This uses the CA Sample Gallery fire-ice-kitchen

 

Here is an example of a Ray Trace after 5 passes ( 2 minutes).

59737f197ed8d_Abode_Fire-ice-kitchen_5passes_lznPS1000.thumb.jpg.97994d297ec1621c88ce075df1e6c286.jpg

 

After 50 passes (20 minutes).

59737f3169cd0_Abode_Fire-ice-kitchen_50passes_lznPS1000.thumb.jpg.823664f8c10a27381d43aa87b0da9215.jpg

 

After 100 passes ( 40 minutes).

59737f48db0c7_Abode_Fire-ice-kitchen_100passes_lznPS1000.thumb.jpg.aba5ba1821895dd52627ffbfe434aeb0.jpg

 

After 2700 passes (18 hours).

59737f5d5682f_Abode_Fire-ice-kitchen_2700passes_lznPS1000.thumb.jpg.91788df2f932dc296f5fead5bbe44ad4.jpg

 

As you can see the differences are not that significant, especially once one exceeds 50 passes. What the passes are doing is some minor lighting & detail refinement and more importantly noise reduction. I have cropped out these pics so you can better see where all the action is.

 

5 passes.

59737f6b9fbe4_Abode_Fire-ice-kitchen_5passes_lznPS1000_GrainCrop.thumb.jpg.3f9d961ba82359f2e38bca882ee1049e.jpg

 

50 passes.

59737f820b919_Abode_Fire-ice-kitchen_50passes_lznPS1000_GrainCrop.thumb.jpg.bb41e65da2f244ac501c7f44397a00b7.jpg

 

100 passes.

59737f948449c_Abode_Fire-ice-kitchen_100passes_lznPS1000_GrainCrop.thumb.jpg.316a3d981cdeb9fc598d764657ab65d1.jpg

 

2700 passes.

59737fa46281b_Abode_Fire-ice-kitchen_2700passes_lznPS1000_GrainCrop.thumb.jpg.b5814bd7a2b2e1c35b4f947f76beb578.jpg

 

Keep in mind that I am cropping in on a fairly low resolution pic for demonstration purposes, the real test is the impact of this has on the normal sized trace. Most of what is happening here is related to detail refinement and noise reduction. This noise(graininess) is predominantly related to two or three conditions, polished materials, predefined metals, situations where light has to pass through more than one transparent material such as glass and poorly lit regions. One way to address noise versus running a huge number of passes is to drop a lower pass pic into a photo editor and apply a bit of noise reduction to it.

 

Original 50 passes.

59737f820b919_Abode_Fire-ice-kitchen_50passes_lznPS1000_GrainCrop.thumb.jpg.bb41e65da2f244ac501c7f44397a00b7.jpg

 

50 passes with some noise reduction.

5973855b7e22f_Abode_Fire-ice-kitchen_50passes_lznPS1000_GrainCrop_NoiseReduction.thumb.jpg.8c45d5a024b5ebb326b9f224efe4cf0d.jpg

 

Original 2700 passes.

59737fa46281b_Abode_Fire-ice-kitchen_2700passes_lznPS1000_GrainCrop.thumb.jpg.b5814bd7a2b2e1c35b4f947f76beb578.jpg

 

The 50 pass trace took 20 minutes, applying noise reduction took about 30 seconds, compare this to running 2700 passes for 18 hours.

 

One way to judge you Ray Trace while running is to click on the + magnifying glass and double it's size, scan the trace for this graininess and when it has diminished sufficiently then you have likely gone as far as you can go.

 

 

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Just in case you are interested and to continue with my emphasis on lighting.

 

Here is the fire-ice-kitchen as per CA's default settings. 26 passes 33 minutes.

59738a1a9288c_CADefault_Fire-ice-kitchen_26passes_PS1000.thumb.jpg.181af43d65c559f95a027429e9cffb49.jpg

 

Here it is with my lighting technique and a minor adjustment to only the polished floor, table and stainless steel material properties. 50 passes 20 minutes.

59738acaddeba_Abode_Fire-ice-kitchen_50passes_lznPS1000.thumb.jpg.56758ebbe76feac9918b6d56c224237d.jpg

 

More passes in less time and improved quality.

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On 7/22/2017 at 10:29 AM, TheKitchenAbode said:

Just in case you are interested and to continue with my emphasis on lighting.

 

Here is the fire-ice-kitchen as per CA's default settings. 26 passes 33 minutes.

59738a1a9288c_CADefault_Fire-ice-kitchen_26passes_PS1000.thumb.jpg.181af43d65c559f95a027429e9cffb49.jpg

 

Here it is with my lighting technique and a minor adjustment to only the polished floor, table and stainless steel material properties. 50 passes 20 minutes.

59738acaddeba_Abode_Fire-ice-kitchen_50passes_lznPS1000.thumb.jpg.56758ebbe76feac9918b6d56c224237d.jpg

 

More passes in less time and improved quality.

 

Yes definitely Interested :)  ............    another really nice Image Graham, and preferable to the Default CA look I think...

 

I tried your Settings on Jintu's "Battle of the Renders" file just now and it looks pretty Nice as is, proving you and He know your way around CA's lighting and RT Settings....

 

Mick.

 

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Glass Speckling and Possible Control Methods
 
I have done an evaluation on this to identify under what conditions these speckels occur and what if any methods are available to eliminate or minimize them.
 
Glass speckling occurs when two individual glass materials or transperant materials overlap in front and behind each other and the intensity of light varies on the surfaces behind the overlapping glass portion. Variations in surface lighting in front of the glass seems to have no effect, it's the surfaces on the other side of the glass and the degree of light variance of those surfaces that impact on this speckling.
 
The degree of speckling is directly porportional to the degree of light variance in those surfaces. The greater the variance(range) the greater the amount of speckling.
 
To date I have not found a direct way to prevent this from occuring, it appears to be a defficiency in the Ray Trace program when dealing with light passing through two or more transparent type materials where they overlap.
 
There are ways to indirectly affect this or minimize it, but they all come with other trade-offs.
 
One is to just eliminate any overly bright surface variations, the less variation the less spekling. The trade of is that you will be very limited in the look of your scene behind the glass.
 
The other method is to make adjustments using the Ambient Oclussion tool in the Ray Trace DBX. The degree of benefit will vary depending upon how severe the speckling is. Keep in mind that this is not the intended use of Ambient Oclussion and that it will effect other light properties due to it's global nature. Also, the Ambient Oclussion does not directly reduce the specking, it's just making it less obvious by altering the dark and bright pixel levels/rage.
 
A way to envision the ambient occlusion tool is to see it like a dynamic range brightness/darkness control. The min and max determine what RGB level the darkest pixel will be represented by and the lightest(brightest) pixel. For maximum dynamic range the RGB value would be 0,0,0 for the darkest and 255,255,255 for the brightest. If one increases the minimum then you are clipping the darkest RGB value to a value greater than 0,0,0. Conversely if you reduce the maximum then you will clip the brightest pixel RGB value to less than 255,255,255. You have reduced the dynamic range. Just to clarify, I'm describing this process in a very simplistic way, the algorithms used are far more complex than just chopping off RGB pixel values, but for a general perspective my description is likely sufficient.
 
As the degree of speckles are directly related to the dynamic range on the surfaces behind it then by using the ambient occlusion control you can reduce this dynamic range and therefore reduce the degree of visible speckels. But, the ambient occlusion is global and therefor it will affect the dynamic range of the entire scene equally. Also, clipping means that the clipped values are lost forever which will effect the data that other adjustment controls will have to work with, such as intensity, contrast, etc. With this in mind you can see the potential drawbacks if the ambient occlusion is not carefully managed. Clipping too much of the darkest regions will result in the dark regions appearing washed out and of coarse clipping the brightest  may give you a dull appereance. Also, as a scene typically contains a much higher percentage of brighter pixels than darker ones there is less tolerence in the minimum setting as you just don't have too many of them that you can afford to loose.
 
The only 100% solution is to not have overlapping glass/transperent materials. If you need the look then it will have to be done without any real overlap. This can be accomplished by having say thee indidual pieces of glass that abutt end to end. The left & right pieces will be the non overlapped portion of the pane and the middle piece will be the overlapped portion. Just change the materials property of the center panel to be a shade darker than the left & right panels. When rendered the scene behind the center panel will be slightly less bright than the scene behind the left & right panels, which represents the extra reduction in light transmission when it has to pass through two layers versus one.
 
 

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Wow.  I'm impressed with your efforts.  My solution is to just tell CA to FIX IT!

Thanks for the explanation.

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Thanks Dennis, Agree but not sure how long that would take.

 

I'm still trying to fully determine the why in all of this. My suspicion is that these types of materials have a certain amount of reflectivity and as such a certain amount of light is trapped between the two panes in a continual bouncing back and forth. The Ray Trace engine only calculates 5 bounces and then gives up. What's curious about this effect is that normally when more than 5 bounces are need the resultant is black, not bright white. This can be seen when one places two opposing mirrors, the fifth reflected image of the opposing mirror is just black.

 

What is also interesting is that if one uses a regular non glass material and sets it's transparency to zero you can still get this effect. I'm wondering if zero is not really zero and for calculation purposes it still being taken into consideration to some very minute extent.

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In case you have been following the "Battle of the Renders" using CA Ray Trace. Here is my result straight out of the Ray Tracer, after some minor adjustments using Photoshop and the comparison Pro Photo.

 

Straight out of Ray Tracer

597ab1f2c104a_Abode_ProPhotoReplication_21000_reducedbrightness.thumb.jpg.c9db6d41b9be536bdfeb47e62ee69dbd.jpg

 

Some minor Photoshop adjustments

597ab206826f0_Abode_ProPhotoReplication_21000PS.thumb.jpg.3f9c7c53a0453a686020cfd3cfebca97.jpg

 

Comparison Pro Photo

05756__Skylights-for-the-modern-eclectic-kitchen-in-white-and-gray.thumb.jpg.6a2e9af254fe3a71a96d1c6f430add9f.jpg

 

I believe this demonstrates that the CA Ray Trace engine can in fact deliver photo realistic renderings.

 

It should also be noted that this rendering was achieved using only basic spot lights and these lights were only adjusted for intensity, cut-off angle, drop rate and shadows on or off. All materials and models are 100% CA. Material properties were tweaked but only for diffusion, reflectivity, roughness and at times some emissivity.

 

The Photoshop version used only basic 101 procedures, a couple of layer masks to adjust lighting in specific regions and to create the shadow effect under the cooker and one curve layer for overall scene brightness/contrast balance.

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Simple straight for ward CA RT on first. 2nd is one click auto adjust in Microsoft Office picture manager.

It gives just the right amount of contrast, most of the time.

RT1.jpg

RT1PP.jpg

Usually I would spend more time on the materials for the cabinets and stainless steel etc but just wanted to do a quickie.

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Dennis - Good example of the benefit and personally the logical decision to utilize some post processing to finish off the scene. In reality this is how it's done, the renderer is just one part of the workflow process in the quest for realism just as the camera has been for decades. Rendering engines are really only a camera substitute, they are data capturing devices. This data is then moved into a data manipulator such as Photoshop. Professional photographers understand that the lighting at the time of the shoot will never be perfect so they do not focus on trying to get the perfect publication grade pic right out of the camera. Instead they use the camera to collect data about the scene through multiple shots at varied exposures, f stops, ISO, etc., each shot capturing different levels of data that would not have been capture through only one setting. Once they have this they no the camera has done it's intended job, the next step is to take this data and put it all together.

 

For true photo realism this is the reality of what it will take and it is also the most efficient way of doing this. Trying to make the necessary final tweaks in the renderer is very inefficient as each change requires one to render the scene again to see the effect, which could take 30 minutes an hour or more. In say Photoshop changes are instantaneous, there is no waiting, you are working in on it live. If a change is too much one can simple reduce the blend % or if a change is just needed in one region of the image then this region can be easily isolated out so only it is effected versus the entire scene. You just can't make these types of adjustments in a rendering engine, if you adjust or add a light to highlight something the light will also impact to some extent on the rest of the scene and there is no way to anticipate in advance as to whether or not this side effect will be desirable.

 

IMO, "resistance is futile", sooner or later some post processing is going to be needed if true photo realism is the objective.

 

 

 

 

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Graham - I just remembered that I also did a tiny tweak to the mid-range settings.  I find this very helpful on certain shots where I don't want the whole picture adjusted across the board.  I am not proficient at these post production programs so just look for some quick, easy and simple built in tools.

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Here's a prime example to demonstrate the value of some post production work.

 

"Battle of the Renders" Competition scene, direct sun set @ 0.5, turned on the ceiling pots (6). Render time 6 minutes.

597d0104d1081_Untitled9h.thumb.jpg.25db80d6cc2a0952baf72cd0366decd9.jpg

 

Dropped it into one of my photo editors, as I have some preset configurations saved I made one click to apply, about 10 seconds.

597d01188b73e_Untitled9h_lzn.thumb.jpg.0bdd7b4e244cce727a08752178c1b3e4.jpg

 

All done! Total time 7 minutes max.

 

 

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Here is the scene adjusted for a late evening look. Added some under-shelf & range hood lights and a few garden lights, all spots. Also changed the backdrop.

 

597ddc8a4d47b_Untitled9hhh_lzn3qtrfblur.thumb.jpg.9192a914b656b28284aed24a0d905ac6.jpg

 

Once the core scene is balanced you can quickly alter it to create whatever look you desire.

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Light Bleed - Impact of Roof and Foundation

 

Here is an example of Light Bleed and how adding a roof and foundation with a floor impacts on the light bleed effect.

 

Please note that this were run with the direct sun at max 50, environmental light at max 100 and color white (255,255,255) which likely represents a worst case situation.

 

No roof, no foundation, 5 passes.

59d1025d0910b_Sun50_EL100_Color100_RoofNo_FoundationNo.thumb.jpg.bdc563b785162eecc478bf9e68a30d4a.jpg

With roof, no foundation, 5 passes. Note reduction in bleed along ceiling/wall intersect.

59d1027787de0_Sun50_EL100_Color100_RoofYes_FoundationNo.thumb.jpg.1191413548c3f7e1a9818a08adbf7094.jpg

With roof, with foundation, 5 passes. Note reduction in bleed along floor/wall intersect.

59d1028d20a7b_Sun50_EL100_Color100_RoofYes_FoundationYes.thumb.jpg.e644ecbbc053da5f1d218d605b398bf5.jpg

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Light Bleed - Ambient Occlusion

 

Here is an example of Light Bleed and the impact ambient occlusion has on the light bleed effect.

 

Please note that this was run with the direct sun at max 50, environmental light at max 100 and color white (255,255,255) which likely represents a worst case situation.

 

Samples were run for 5 passes, no roof or foundation.

 

Ambient Occlusion - Min = 0, Max = 10

59d2434ed2932_Sun50_EL100_Color100_RoofNo_FoundationNo_OCmin0max10.thumb.jpg.67da9eb1b9b0fe66d59ab0fb277a1c13.jpg

 

Ambient Occlusion - Min = 0, Max = 1

59d2440424bdc_Sun50_EL100_Color100_RoofNo_FoundationNo_OCmin0max1.thumb.jpg.130cdf277ae7c825a81b1696ca87b5f9.jpg

 

Ambient Occlusion - Min = 4, Max = 5

59d244ac2d243_Sun50_EL100_Color100_RoofNo_FoundationNo_OCmin4max5.thumb.jpg.618642aba014bbcaf8e7ec37c42adef3.jpg

 

Ambient Occlusion - Min = 5, Max = 10

59d244f8d4bd1_Sun50_EL100_Color100_RoofNo_FoundationNo_OCmin5max10.thumb.jpg.e77312c46f3c0b867eb53fa5b0283b54.jpg

 

Ambient Occlusion - Min = 7, Max = 10

59d24589e3d1f_Sun50_EL100_Color100_RoofNo_FoundationNo_OCmin7max10.thumb.jpg.409e01406bd34a9bd8751f79ca2691b8.jpg

 

Ambient Occlusion - Min = 9, Max = 10

59d245a8ccc51_Sun50_EL100_Color100_RoofNo_FoundationNo_OCmin9max10.thumb.jpg.9c18d4075d22402b8bb99517251b943c.jpg

 

Within this test grouping no significant reduction in the degree of light bleed was realized regardless of the ambient occlusion min/max settings.

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4 hours ago, TheKitchenAbode said:

Light Bleed - Ambient Occlusion

 

Here is an example of Light Bleed and the impact ambient occlusion has on the light bleed effect.

 

Please note that this was run with the direct sun at max 50, environmental light at max 100 and color white (255,255,255) which likely represents a worst case situation.

 

Samples were run for 5 passes, no roof or foundation.

 

 

 

Within this test grouping no significant reduction in the degree of light bleed was realized regardless of the ambient occlusion min/max settings.

Graham, appreciate your time as always, the problem I have is that by definition ambient occlusion should darken the corners of the room. Which tells me that either the AO engine needs to be rebuilt or more importantly, the bleeding needs to be addressed from a physical standpoint. Close the gaps at the corners and then test AO...if it doesn't create better depth and higher contrast in the corners then AO needs a rework as surface's aren't projecting properly.

Also, environment light from Raytrace is a tricky thing, it tends to give light to areas that should have heavier shadow, such as underneath a freestanding range with no direct light.

A simple work-around fix for the physical model would be to auto-generate an L-shaped 3/4" molding with a 3/4" Horizontal and vertical offset to close in the corners.

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17 hours ago, Renerabbitt said:

Graham, appreciate your time as always, the problem I have is that by definition ambient occlusion should darken the corners of the room. Which tells me that either the AO engine needs to be rebuilt or more importantly, the bleeding needs to be addressed from a physical standpoint. Close the gaps at the corners and then test AO...if it doesn't create better depth and higher contrast in the corners then AO needs a rework as surface's aren't projecting properly.

Also, environment light from Raytrace is a tricky thing, it tends to give light to areas that should have heavier shadow, such as underneath a freestanding range with no direct light.

A simple work-around fix for the physical model would be to auto-generate an L-shaped 3/4" molding with a 3/4" Horizontal and vertical offset to close in the corners.

My test was extreme with the sun and environment light set to the max. Suspect this may have reduced the effectiveness of the Ambient Occlusion. The light bleed is problematic but can be controlled. The determining factors appear to be the intensity of the direct sun and the intensity of the environment light in combination with the luminosity of the two light sources and then of course as to whether one has a roof and/or foundation in place. Given the number of variables it can be challenging to find the right combination. I think another issue relates to the control range of the direct sun and environment light, the direct sun has a range of 0 - 50 and the environment light 0 - 100. It is easy to assume that one should be able to utilize these control ranges to their max under all circumstances, I'm not certain that is the case. From my limited experimentation it appears that the luminosity of the light source will dictate whether one can use the full control range without introducing light bleed. 

 

Environment Light Color 255,255,255 Luminosity 100%, direct sun = 50, environment light = 100

59d38521e76cc_Sun50_EL100_Color100_RoofYes_FoundationYes.thumb.jpg.047c45fe53b955962481d5c42aa45d31.jpg

 

Environment Light Color 255,255,255 Luminosity 25%, direct sun = 50, environment light = 100

59d38532d9ce1_Sun50_EL100_Color25_RoofYes_FoundationYes.thumb.jpg.8402249fa46dbaaf61dcd2011b576e18.jpg

 

As I continue to explore Ray Trace, for better or worse, I find myself constantly coming back to the same conclusion; it can do a reasonably good job, "but" it only can do what it can do with what you give it.

 

It can look like this

59d39c6617733_Sun50_EL100_Color100_RoofNo_FoundationNo.thumb.jpg.0ae868880bfe9c987739c494da7671ea.jpg

 

or look like this

59d39c7c41a74_Untitled1.thumb.jpg.e20be43b3312d9a09f83d97564cf1235.jpg

 

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Light Bleed - Conclusions

 

I have now run a wide range of tests concerning this issue. Here are my conclusions and recommendations based upon what I have seen so far.

 

Conclusions

- Light bleed occurs on the interior when the exterior lighting luminosity(brightness) is too intense.

- When it results from the Direct Sunlight, bleeding occurs primarily along wall & ceiling intersects.

- When it results from the Environment Light, bleeding occurs primarily along wall & floor intersects and underneath floor placed items.

 

Direct methods to control Direct Sunlight bleed

- Place a roof on the structure. This works due to the fact that the roof and overhangs cast exterior shadows in the most vulnerable bleed regions. These shadows are just areas of lower luminosity.

- Reduce the intensity of the direct sunlight. This can be done one of two ways, reduce the slider setting or reduce the luminosity level of the suns color.

 

Indirect Methods to control Direct Sun bleed

- If not too severe then adjusting the ambient occlusion may help. Dependent upon the settings this can reduce the contrast in the wall & ceiling region which will therefore affect the bleeds visibility.

- Increase the interior ambient light level. Again this will reduce contrast and will therefore affect the bleeds visibility.

 

Direct methods to control Environment Lighting bleed

- Place a foundation with a floor under your structure. Works for similar reasons as stated for the direct sun. Also, though not fully explored as of yet, the presence of a terrain also seems to have an impact.

- Reduce the intensity of the Environment Lighting. There are four ways to due this, reduce the slider setting. If it is set to "Use Color" then the luminosity level of the color can be reduced. Select the "Use Sky" option or select the "Use Backdrop Image", these work as their level of luminosity is much lower than the default RGB 255,255,255 luminosity.

 

Indirect Methods to control Environment Lighting bleed.

- Same as those above for the Direct Sun

 

To summarize, it's all about the level(degree) of luminosity that the exterior is being subjected to, when set too high light bleed will result. This does not preclude one from creating interior lighting effects of direct and indirect exterior lighting, it just means that there are limitations as to how far you can go through the use of the Direct Sun and Environment lighting controls. Consider using parallel lights to amplify the direct sun effect or 3D point and spots to simulate the environment lighting effect.

 

Hope this helps.

 

 

 

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I think Grahams opinions are not simply conjecture, but based on scientific research methodologies and findings.I always test and find your experiments very helpful.

thumps up sir.

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2 hours ago, yusuf-333 said:

I think Grahams opinions are not simply conjecture, but based on scientific research methodologies and findings.I always test and find your experiments very helpful.

thumps up sir.

 

Thanks Yusuf. Yes I do attempt to utilize a scientific methodology in my tests, It's due to spending at least 15 years in a research and development environment. When I make these statements they are not based upon random daily experiences. I devise specific tests to identify and isolate what I'm attempting to observe and understand. Any conclusion I surmise is then tested for repeatability and predictability. This does not mean that every possible interaction has been explored or verified but it does tend to provide a reasonable weighting value as to the fundamental validity of what has been observed and the drawn upon conclusions. 

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Speckles(fireflies) in Glass

 

I have taken a closer look at the issue of speckles(fireflies) forming on glass materials. Here are my results, thoughts and recommendations.

 

These annoying speckles seem to occur under one specific scenario. There must be at least two glass layers overlapping each other, photon mapping must be "On" and there must be a region that is viewable through the glass where there is a variance in a level of reflective light coming from the surface.

 

59ea05e0287cf_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7.thumb.jpg.b75ba00ec41ad3be12757d3215a6a85a.jpg

 

In pondering what is really going on here I have concluded the following:

 

The term speckles(fireflies) is likely incorrect. We should be calling this "Black Holes", it seems to be the inverse that's really the issue. Why? when photon mapping is turned on the path of a light ray is computed for 5 iterations(bounces), as glass has a reflective property there will always be a portion of light that will be bounced back to the other opposing layer of glass and then this glass layer will bounce back a portion of that light back. In other words there will always be a portion of light that is essentially trapped between the glass layers in a infinite bouncing back and forth between these opposing glass surfaces. For the camera to see the light ray it must get back to the camera within 5 bounces, if not the camera does not receive that ray of light, no ray of light means black.

 

If you wish to see the best example of this then take two opposing mirrors where one mirror is visible within the other. Run a Ray Trace with photon mapping on and after 5 visible reflections in the mirror the 6th expected reflection will just be black. The engine will not calculate beyond the 5th bounce and a 6th reflection would mean the light ray would not be received by the camera within this 5 bounce limit.

 

What can we do to overcome this?

This one was very challenging, as in all of my tests I was unable to find anything such as material properties, ambient occlusion or Ray Trace duration that would have any significant direct effect. I'm not saying that these won't have any benefit at all, but I found the benefit to be minor and when using these to control the "Black Hole" formation they, being global type settings, also altered many of the unrelated aspects of the scene. When something such as ambient occlusion is being used to address this what you are really doing is just changing the contrast ratio in your scene. If the contrast ratio of the scene is lowered then the difference in luminosity between the brightest regions and darkest regions has been compressed and as such it is less visible, still there just not as obvious.

 

Of coarse one could just turn off photon mapping but this also changes the entire look of your scene. You could also eliminate that background light variance but again you may be compromising your desired look. You could also just avoid double glass layer situations but then again you will restrict the models in your scene, no more glass pendants that's for sure. Personally these are not acceptable trade-offs.

 

All is not Lost!!!

I did however find one and only one procedure that allowed me to maintain all of my desired scene properties while at the same time make those "Black Holes" collapse.

 

"Run the scene at a higher resolution and then resize it down."

 

15 passes run at 1200px X 600px, my normal print size.

59ea05e0287cf_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7.thumb.jpg.b75ba00ec41ad3be12757d3215a6a85a.jpg

 

15 passes run at 4800px X 2400px, resized back to 1200px X 600px.

59ea05f36b70f_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7_4800X2400_188min_1200X600.thumb.jpg.c04ff37ca52522f2c04e6c16b59fd6d9.jpg

 

15 passes run at 9600px X 4800px, resized back to 1200px X 600px.

59ea060d82930_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7_9600X4800_188min_1200X600.thumb.jpg.aef426bb975242210d177fba47995d96.jpg

 

Why does this work. I believe it's all in the resizing algorithms. From a simplistic view point, when you downsize a pic the algorithms must make as best a pic as possible with fewer pixels. To do this they analyze two or more adjacent pixels and extrapolate a new single pixel that best represents their blending together. If the two original adjacent pixels have a significant variance in luminosity then the new single pixel will likely be halfway in the luminosity difference between the two original pixels, It can perform a bit like a very sophisticated contrast control that works on a pixel by pixel based analysis.

 

There is however one price to pay for this, as you increase your Ray Trace pixel count it will take longer for the engine to calculate those additional pixels. Double the pixel width and height and the time per pass will quadruple as there are now 4 times the number of pixels to process.

 

The first scene above took about 12 minutes at 1200 X 600

The second scene above took about 47 minutes at 4800 X 2400

The third scene above took about 188 minutes at 9600 X 4800

 

This negative time impact can be reduced due to the fact that increasing the number of pixels often reduces the number of passes needed to generate a clean scene when resizing down and as such, though you pay a per pass time penalty there is some compensation as fewer passes may be needed. Total time = time per pass X the number of passes.

 

Resized 9600 X 4800, 15 passes, 188 minutes.

59ea1e2e170a6_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7_9600X4800_188min_1200X600.thumb.jpg.b507dc1fd143b6d78422b724b71771ca.jpg

 

Resized 9600 X 4800, 3 passes, 37 minutes.

59ea244b8ed9f_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7_9600X4800_37min_1200X600_3PassesPS.thumb.jpg.e3c83fd23d5735235f5ac170f3d620d6.jpg

 

Original 1200 X 600, 15 passes, 12 minutes.

59ea24d4d6540_GlassSpeckles_ForgroundlightsOn_BackgroundLightsOn_100_AO0-7.thumb.jpg.aef68375a7bade664442aa6071e972a5.jpg

 

Though I was not able to get my time down to the originals 12 minutes, I was able to reduce the first high resolution run of 15 passes 188 minutes down to 3 passes in 37 minutes while maintaining about 90% of the longer hi resolution scenes quality. Though not perfect it is significantly better than the bottom regular pixel sized pic.

 

Hope this proves helpful.

 

 

 

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On 7/13/2017 at 2:35 PM, TheKitchenAbode said:

Exterior Lighting

 

I have mentioned in past postings that on interior renderings the direct sun feature lacks the ability to simulate the effect of indirect light entering into the interior.

 

This scene has the direct sun set at 15.

5967b20340032_Untitled5_lzn900.thumb.jpg.ccffa13e8c47f6fc5a538482186426ea.jpg

 

This one is the same but with my indirect light simulator turned on.

5967b93357e0e_Abode_five-12-kitchen_75pass_lzn_900.thumb.jpg.e389ac876552719bc438d459c9e6b05d.jpg

 

With this, the direction, spread, light color and intensity of the indirect exterior lighting effect can be controlled independently from the direct sun setting.

 

This effect can't be accomplished using the environment lighting option. Environment lighting is intended as a means to control the exterior shadow depth only, it allows one to simulate softer exterior shadows with an overcast sky versus a clear sky. Using this to brighten an interior will lead to a washed out scene and some major light bleeding problems when foundations do not have floors or are slab on grade type.

 

Now if you could just post a tutorial on what you did here, that would be a miracle. This is perfect.

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21 minutes ago, BruceBoardman said:

Now if you could just post a tutorial on what you did here, that would be a miracle. This is perfect.

 

I have been trying to do that through a series of specific articles concerning a number of issues that impact on the quality of a Ray Trace. Unfortunately there is no single set of settings per say, in other words many of the available settings have a level of interdependency. This interdependency gives a high level of credence to the importance of obtaining the right balance in order to obtain the look you desire. Having said that there is hope, given what I have posted, in conjunction with a significant amount of non-posted techniques I been able to eliminate a significant amount of playing around that now allows me to just drop in my preconfigured lights, set my Ray Trace settings essentially the same and generate a decent Trace on a consistent basis. Should a situation arise where the results are not as expected I'm usually able to quickly identify the culprit and adjust it accordingly, this is why it is important to understand why things do what they do. Over the next while I will post more about each light type and how to configuring them to obtain a particular look. Hopefully when all is said and done everyone will be able to take from this what is important to them to generate the look they desire.

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3 minutes ago, TheKitchenAbode said:

 

I have been trying to do that through a series of specific articles concerning a number of issues that impact on the quality of a Ray Trace. Unfortunately there is no single set of settings per say, in other words many of the available settings have a level of interdependency. This interdependency gives a high level of credence to the importance of obtaining the right balance in order to obtain the look you desire. Having said that there is hope, given what I have posted, in conjunction with a significant amount of non-posted techniques I been able to eliminate a significant amount of playing around that now allows me to just drop in my preconfigured lights, set my Ray Trace settings essentially the same and generate a decent Trace on a consistent basis. Should a situation arise where the results are not as expected I'm usually able to quickly identify the culprit and adjust it accordingly, this is why it is important to understand why things do what they do. Over the next while I will post more about each light type and how to configuring them to obtain a particular look. Hopefully when all is said and done everyone will be able to take from this what is important to them to generate the look they desire.

Amen. This is my goal. 

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1 minute ago, BruceBoardman said:

Amen. This is my goal. 

 

Mine too!!!

 

Here is an example. Note that the materials and models here are all CA, any adjustments to their properties are few and when done they are normally just a minor adjustment to their reflectivity. All lighting is done with only spot lights. Renders in about 30 minutes. Just need to change the wood grain direction on the table.

 59f9ec6f92040_Concept5e_lzn.thumb.jpg.f75faca50638bc12a6477698a764d4d4.jpg

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