Fireflys on architectural interior, Max ray intensity does not resolve issue.

[DeadLift315]

Hello!

My team and I are running into issues with fireflies on several objects in an architectural interior animation. Please see the attached clip for reference. It is most noticeable in the clay pot, silverware, and some glass objects in the scene.



I know that enabling sub pixel mapping will resolve the issue but would prefer to avoid this if there is another solution. I really would hate to lose the highlights. In the example frames the max ray intensity is set to 20 and we cranked up the min shading rate extremely high (80) to see if that would make any improvement. While the shade rate does appear to help, it did not solve the issue.

Use local subdivisions is off and our render settings are only slightly modified from the new defaults in v-ray 3.4. The color mapping is linear and clamping is disabled. In our pipeline we use real world luminous power values on all of our v-ray lights, and use the v-ray light meter to gauge the LUX emitted by exterior HDRI lighting. My understanding is that fireflies are typically caused by very intense lights in the scene, which I do not think is the issue in this case.

If anyone has any solutions or ideas I would greatly appreciate it!

Thank you for your help!

[LudvikKoutny]

Min shading rate won't help here I am afraid. If anything, lowering it could help. The issue here is most likely sampler not being able to pick up the fine highlight on the vase, and then adaptivity reducing chance of that highlight ever being discovered. What should help is increasing min subdivs. I would also revert MSR back to 6

[Morbid Angel]

Is there anything special about that pot? it does not look like a typical firefly to me...

[DeadLift315]

Thank you for the help!

I tried increasing the min subdivisions. I went as high as 12 but did not notice any reduction of fireflies. shading rate is back down to 6

I initially thought the same thing about the clay pot. I opened the pot up in slate and it is a very basic v-ray material with bitmaps for diffuse, reflection, bump, and reflection gloss. While the part of the pot where the sparkles are appearing is reflective and has sharp glossy reflections nothing appears out of the ordinary. I am still pretty sure that this is a firefly issue as turning sub pixel on does fix the problem. Setting the max ray intensity to a low value (3) reduces the overall brightness of the image, but does not clean up the fireflies.

[Syclone1]

Is there anything special about that pot? it does not look like a typical firefly to me...

I have to agree, it almost looks like a reflection from a pot light in the ceiling and the reason its moving so much over a few frames is because of the curvature of the top of the pot distorting the reflection. As a test I would move the pot to the right a couple feet and see if the 'firefly' either goes away or stays and changes position on the pot, the latter would indicate to me that it is a reflection and not a render error.

-dave

[Alan Iglesias]

A little Intensity-based lens effect might help with these sorts of things...

-Alan

[DeadLift315]

I went back and looked closer at the pot, silver ware, and glass materials in the scene. They are definitely the causing the "firefly" like sparkling effect . I have no idea why (as almost all of the assets we use come from evermotion or some other model supplier) but the Fresnel was set to 10 on the pot and metal for the silver ware. Adjusting this to a realistic value solved the issue on those objects. for the lamps and glass vase the materials appeared to be made logically set up but recreating a new v-ray material for them caused the issue to stop. I am not sure if they were some how corrupted but it is highly possible that these were made with v-ray 1.5 or earlier.

Unfortunately the company I work for is utilizing an asset library that has some really old and not necessarily well made objects in it. Enabling sub pixel mapping has been a standard practice in their renderings for as long as the option has been available. In trying to move forward with better render settings and disabling it we took away the option that was covering up these issues.

Thank you all again for your help.