strange Shader´s reflection behaving

[caypiranha]

Hi Guys,

1. Increasing the value one by one behaves quite reproducible after Value "3". Until there, you can see it very barely shining through the rough coating before it breaks through on Value 3
But from 0-3 it´s really wired/wrong looking and pops up in 3 Steps from almost totally rough to super glossy:





What are the reasons for that?

[caypiranha]

2. Here is another thing, that appears when turning on fresnel reflection






are these both may be from the same "bug" family as mentioned already here? -> https://forums.chaos.com/forum/v-ray...specular-color

[caypiranha]

... and even the highlight will be eaten from this black hole. It was in this case the size multiplier from physical sun. The values here are: 25 to 50 and 70. At ~100 the remaining highlight totally dissapears. (btw.: dont mind about the horizontal line on the lower shpere part, wich is due to a invisible plane not important)

[hermit.crab]

Regarding the first issue: I cannot reproduce this behavior (tested with V-Ray 5, update 2.2); the specular effect is gradually increased with each value change. Does it render correctly? Try updating the preview swatch.
Regarding the second issue: I am not entirely certain I understand what you mean. Could you elaborate? Otherwise, it is normal for larger sun sizes to yield softer shadows and highlight reflections.

[caypiranha]

Regarding the first issue: I cannot reproduce this behavior (tested with V-Ray 5, update 2.2); the specular effect is gradually increased with each value change. Does it render correctly? Try updating the preview swatch.

and you started from 0-4 on the Values of the color wheel? (btw. using same versions here as well)
autom. Update is present in Slate and Render view simultaneously. Swatchpreview is not necessary

Regarding the second issue: I am not entirely certain I understand what you mean. Could you elaborate? Otherwise, it is normal for larger sun sizes to yield softer shadows and highlight reflections.

ok, maybe first maybe forget about the Sun...=)
the problem comes with every Light and is about the black shading poor circle which decreases size when going up from 0-25 (again, Value on the color wheel) - this time Fresnel enabled. (The disappearing power in the black eye of the sun decreasing its size multiplier is just another observation & I understand what you mean)

...but anyway, here we go with the scene:

[hermit.crab]

Both effects are caused by the Cutoff (Options tab) value, which acts as a threshold below which reflections/refractions are not traced. Set it to 0.001 to get the expected results.

[kosso_olli]

This issue is caused by outdated cutoff values and default VrayMtl settings.
These here in your shader are the old ones. Create a new VrayMtl from scratch and compare the defaults.

[bardo]

have you checked your "Cutoff" setting in Options of the VrayMat?
Try to lower a bit until you fix the reflection

[caypiranha]

thanks, guys - yes that´s it =)

Those materials really came from my own material library I used now many years.
(The good thing on them is, their opacity mode is set to stochastic, which as the new default setting causes apparently some different problems...)


btw.: what´s that Cutoff setting really useful for?

[bardo]

btw.: what´s that Cutoff setting really useful for?

As any cutoff, is useful to "cut" calculations when pixel values are under that threshold.
This is for reflection/refraction but it exists for lights too.


From manual https://docs.chaos.com/display/VMAX/...RayMtl-Options
"Cutoff – Specifies a threshold below which reflections/refractions are not traced. V-Ray tries to estimate the contribution of reflections/refractions to the image, and if it is below this threshold, these effects are not computed. Do not set this to 0.0 as it may cause excessively long render times in some cases. This parameter is not available when the renderer is set to GPU."

[caypiranha]

Thanks for the hint bardo. I once tested it a bit, but haven´t seen a big advantage of adjusting this setting suitable for probably faster render or I never went in the situation to take massive use of it.
So maybe I need to make a scene where much more Raytracing (transp. & refraction) happens.

[^Lele^]

Thanks for the hint bardo. I once tested it a bit, but haven´t seen a big advantage of adjusting this setting suitable for probably faster render or I never went in the situation to take massive use of it.
So maybe I need to make a scene where much more Raytracing (transp. & refraction) happens.

Or a scene where the stuff you're lighting up close is also lit by far-away lights, or when your glossy reflective object is getting busy needlessly by very faint reflections.
The latter is less of an issue these days, as the adaptive sampling puts price to it, and that's also why since the old days the cutoff has been lowered to an invisible 0.001.

[caypiranha]

...and that's also why since the old days the cutoff has been lowered to an invisible 0.001.

thanks Nele for this Info. I will keep it in mind. (specially what you mentioned before my quote here)
But never the less, is there a kind of script, that changes from 0.01 to 0.001?
When loading all scenes, or using my Mats from my Matlibs, I feel I always want to change it - just in case. But it takes useless time somehow... =)

[^Lele^]

for m in (getclassinstances vraymtl) do m.option_cutOff = 0.001

The above will forcefully change the cutoff of all the materials in the loaded scene to 0.001

[caypiranha]

oh thanks a lot! =) works perfect indeed

in Maya it is possible to drag and drop script snippets directly to Buttons. How should I do doing in Max so? I saved it now as am *.ms scripts
(using the Kenzors Script navigator for such cases. it is also fine for that amount of needs - just wondering again why no useful implementation has been done to max as well)