PhotonGI cache

Discussion related to the Engine functionality, implementations and API.
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lacilaci
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Re: PhotonGI cache

Post by lacilaci » Sat Feb 09, 2019 1:32 pm

Dade wrote:
Sat Feb 09, 2019 1:10 pm
lacilaci wrote:
Sat Feb 09, 2019 6:26 am
I don't know what vray's retracing does though
I have the strong feeling V-Ray "retrace" is my fall back to normal path tracing solution. I use a comparison between ray length and cache look up radius, they may use the provided user parameter instead but I have the feeling it is the same trick.

Yes, ive read some docs and they say it is using brute force near corners. I just don't know how it relates to reflection as they often mention this feature fixes reflection of cache too

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lacilaci
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Re: PhotonGI cache

Post by lacilaci » Sat Feb 09, 2019 1:43 pm

btw could you interpolate between samples? vray does and since there ist brute force near corners we dont have to be afraid of light leaks.

they also use some sort of pre-filter, not sure whats that about.

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B.Y.O.B.
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Re: PhotonGI cache

Post by B.Y.O.B. » Sat Feb 09, 2019 1:44 pm

lacilaci wrote:
Sat Feb 09, 2019 6:26 am
Can there be some cache filtering for reflections?

Wanted to test older scenes wigh gi cache but there is no way I'm going through all materials and deciding if they need to have photongi disabled.
And probably every complex scene will have a ton of glossy materials that won't work with gi caching because of the reflections.
I would also prefer an automatic solution a lot.
In the worst case, compute the min/max values in every roughness texture and decide on this if cache should be disabled or not.
If it takes long to compute, it could be added as a special function which can be called from the Blender addon via a button ("auto-calculate PhotonGI settings of materials").
lacilaci wrote:
Sat Feb 09, 2019 6:26 am
And one suggestion for blender addon. The lower limit for photon cache settings seems to be 1000. Wouldn't it make sense to have a [number field] and letter "K" behind it? Suggesting this is numer x 1000 so that users don't input numbers like one hundred million :D? Or do you think it would look messy in the UI? Maybe just a tooltip that the numbers are in thousands? I just feel silly counting the number of zeroes so that I don't accidentaly use billion of photons :D
I'll probably implement something like this, but Blender doesn't allow me to draw custom text behind a number, so I'll have to find some other way to show the hidden multiplier.
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lacilaci
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Re: PhotonGI cache

Post by lacilaci » Sat Feb 09, 2019 1:49 pm

B.Y.O.B. wrote:
Sat Feb 09, 2019 1:44 pm
lacilaci wrote:
Sat Feb 09, 2019 6:26 am
And one suggestion for blender addon. The lower limit for photon cache settings seems to be 1000. Wouldn't it make sense to have a [number field] and letter "K" behind it? Suggesting this is numer x 1000 so that users don't input numbers like one hundred million :D? Or do you think it would look messy in the UI? Maybe just a tooltip that the numbers are in thousands? I just feel silly counting the number of zeroes so that I don't accidentaly use billion of photons :D
I'll probably implement something like this, but Blender doesn't allow me to draw custom text behind a number, so I'll have to find some other way to show the hidden multiplier.
literaly just tooltip on mouse over that the value is in thousands... user dont need to use or know precise numbers

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lacilaci
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Re: PhotonGI cache

Post by lacilaci » Sat Feb 09, 2019 2:50 pm

B.Y.O.B. wrote:
Sat Feb 09, 2019 1:44 pm
lacilaci wrote:
Sat Feb 09, 2019 6:26 am
Can there be some cache filtering for reflections?

Wanted to test older scenes wigh gi cache but there is no way I'm going through all materials and deciding if they need to have photongi disabled.
And probably every complex scene will have a ton of glossy materials that won't work with gi caching because of the reflections.
I would also prefer an automatic solution a lot.
In the worst case, compute the min/max values in every roughness texture and decide on this if cache should be disabled or not.
If it takes long to compute, it could be added as a special function which can be called from the Blender addon via a button ("auto-calculate PhotonGI settings of materials").
No, please no workarounds on top of workarounds... even the existence of switch to turn off cache per material seems like a step in wrong direction.

My own opinion is, that the whole alpha0 should be postponed until cache is carefree to use for new users, otherwise it's gonna backfire and people will just complain. No release is better than bad release imho. And I think a bug or suboptimal performance is going to be tolerated way more than weird workarounds for semi finished features... Again, just my opinion on the matter.

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Re: PhotonGI cache

Post by Racleborg » Sat Feb 09, 2019 3:32 pm

No release is better than bad release imho
I agree

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Dade
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Re: PhotonGI cache

Post by Dade » Sat Feb 09, 2019 9:52 pm

From V-Ray documentation (https://docs.chaosgroup.com/display/VRA ... e+Settings):
Retrace – Enables retracing of GI near corners. This helps prevent light leaks and flickering. Normally, this should be enabled. The value specifies the extent to which GI near corners are retraced instead of being read from the light cache. A value of 0.0 disables retracing. A value of 2.0 is good for still images, and 8.0 is good for animations. Higher values will result in more rays traced at render time. For more information, see the Retrace example below.
So I'm using exactly the same solution but I'm using a fixed scale factor of 2.0 x <cache lookup radius> while the expose the "2.0" as a user defined parameter so it can be adjusted. I will do the same.

About Glossy material:
The second scene in this example shows how the Retrace option can be used to improve the appearance of glossy reflections and refractions with the Use for glossy rays option. In this case, V-Ray dynamically decides whether to use the light cache or not, based on the glossiness of the surface and the distance from it.
So they use both the distance and the roughness. I can do the same.
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lacilaci
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Re: PhotonGI cache

Post by lacilaci » Sat Feb 09, 2019 10:09 pm

that sounds great.
If reflections get solved, then maybe we would only need to figure a still image defaults and animation-stable defaults for gi cache.

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Re: PhotonGI cache

Post by B.Y.O.B. » Sat Feb 09, 2019 10:35 pm

Yes, this sounds like a good plan.
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Re: PhotonGI cache

Post by Sharlybg » Sun Feb 10, 2019 12:19 am

Promising !
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