Unexpected rectangles; Missing sky reflection

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FarbigeWelt
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Unexpected rectangles; Missing sky reflection

Post by FarbigeWelt » Tue Nov 19, 2019 12:05 am

openCL, path, different settings.

1) There appear unexpected rectangles rendering with optional light tracing.
2) Reflection of sky on water's surface disappears when rendering with pgic caustic cache is enabled.
light tracing, two unexpected brighter rectangles
light tracing, two unexpected brighter rectangles
Fountain A, no pgic caustic, no light tracing
Fountain A, no pgic caustic, no light tracing
Fountain A, pgic caustic, no light tracing
Fountain A, pgic caustic, no light tracing
Fountain 12, no pgic caustic, light tracing
Fountain 12, no pgic caustic, light tracing
1) Where come these rectangles from with light tracing?
2) Why disappears the reflection of the sky with pgic caustic cache?
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Dade
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Re: Unexpected rectangles; Missing sky reflection

Post by Dade » Tue Nov 19, 2019 9:57 am

FarbigeWelt wrote:
Tue Nov 19, 2019 12:05 am
1) Where come these rectangles from with light tracing?
It looks like a numerical precision problem, is the bottom of the pool touching the ground ? How is modeled the water ?Try to rise the poll a little and/or to lower the water a little.
FarbigeWelt wrote:
Tue Nov 19, 2019 12:05 am
2) Why disappears the reflection of the sky with pgic caustic cache?
Hard to say without a test scene to check what materials are you using etc.
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FarbigeWelt
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Re: Unexpected rectangles; Missing sky reflection

Post by FarbigeWelt » Tue Nov 19, 2019 9:07 pm

Dade wrote:
Tue Nov 19, 2019 9:57 am
FarbigeWelt wrote:
Tue Nov 19, 2019 12:05 am
1) Where come these rectangles from with light tracing?
It looks like a numerical precision problem, is the bottom of the pool touching the ground ? How is modeled the water ?Try to rise the poll a little and/or to lower the water a little.
I replaced the mesh of the water with a simpler version. Still the rectangles appear with light tracing.
Dade wrote:
Tue Nov 19, 2019 9:57 am
FarbigeWelt wrote:
Tue Nov 19, 2019 12:05 am
2) Why disappears the reflection of the sky with pgic caustic cache?
Hard to say without a test scene to check what materials are you using etc.
Here, is a simpler version of the scene.
Fountain, simplyfied.7z
Fountain, simplified
(519.51 KiB) Downloaded 5 times
The following pictures have been rendered with this scene.
1_Fountain, no light tracing, no pgic caustics cache.png
1_Fountain, no light tracing, no pgic caustics cache.png
2_Fountain, with light tracing, no pgic caustics cache
2_Fountain, with light tracing, no pgic caustics cache
3_Fountain, no light tracing, with pgic caustics cache
3_Fountain, no light tracing, with pgic caustics cache
4_Fountain, with light tracing, with pgic caustics cache
4_Fountain, with light tracing, with pgic caustics cache
5_Fountain, no subdivision, no light tracing, with pgic caustics cache
5_Fountain, no subdivision, no light tracing, with pgic caustics cache
6_Fountain, no light tracing, with pgic caustics cache, look up 0.05m
6_Fountain, no light tracing, with pgic caustics cache, look up 0.05m
7_Fountain, shade flat, no light tracing, with pgic caustics cache
7_Fountain, shade flat, no light tracing, with pgic caustics cache
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Dade
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Re: Unexpected rectangles; Missing sky reflection

Post by Dade » Wed Nov 20, 2019 8:54 am

It is a numerical precision problem, your scene is several kilometers large while you are looking only to few meters. Just set the minimum epsilon value to "0.01" and it will render fine. The other option is to increase the distance between water, pool bottom and ground.

The problem is noticeable with light tracing because the ray are traced from the sky (i.e. the border of the scene) so they start far away from your camera. You were literally looking at the bits of the floating point 32bit precision.
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Re: Unexpected rectangles; Missing sky reflection

Post by FarbigeWelt » Fri Nov 22, 2019 7:50 pm

Dade wrote:
Wed Nov 20, 2019 8:54 am
It is a numerical precision problem, your scene is several kilometers large while you are looking only to few meters. Just set the minimum epsilon value to "0.01" and it will render fine. The other option is to increase the distance between water, pool bottom and ground.

The problem is noticeable with light tracing because the ray are traced from the sky (i.e. the border of the scene) so they start far away from your camera. You were literally looking at the bits of the floating point 32bit precision.
Thank you for the information, Dade. Epsilon of 0.0005 is already enough to remove the precision based rectangles.
Still the question remains, why removes PGIC caustic cache the surface reflections.
The minimum radius is rather important to be set correctly, at least what I observed with the fountain scene. To small leads to strange shadows.

Light tracing only, with surface reflections
Fountain, new water, 800 samples, epsilon 0.0005, light tracing_01m40s
Fountain, new water, 800 samples, epsilon 0.0005, light tracing_01m40s
Light tracing and PGIC caustic cache, missing surface reflections, good choice of radius
Fountain, new water, 800 samples, epsilon 0.0005, light tracing, pgic caustic radius 5cm..5mm_10m07s
Fountain, new water, 800 samples, epsilon 0.0005, light tracing, pgic caustic radius 5cm..5mm_10m07s
Light tracing and PGIC caustic cache, suboptimal choice of radius
Fountain, new water, 800 samples, epsilon 0.0005, light tracing, pgic caustic radius 2.5cm..0.5mm_09h45s
Fountain, new water, 800 samples, epsilon 0.0005, light tracing, pgic caustic radius 2.5cm..0.5mm_09h45s
:?: Why is there no surface reflection with PGIC caustic cache enabled :?:
Light and Word designing Creator - www.farbigewelt.ch - aka quantenkristall || #luxcorerender
160.8 | 42.8 (10.7) Gfp | Windows 10 Pro, intel i7 4770K@3.5, 32 GB
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Dade
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Re: Unexpected rectangles; Missing sky reflection

Post by Dade » Sat Nov 23, 2019 10:28 am

For what I see, the reflection is still there:

Image
Image

The underwater of the pool is just nearly black without PGI because no SDS path can be rendered and the reflection is pretty much the only part rendered (and it is more evident).
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