PBR GLASS Black areas

[blackchicken]

Hello,

I dont understant this effect. If I render in PBR, and have a closed object, when is touching another or intersect with, glass object has black colour. Refl Refr limit is 10 Diff 2 . Where is problem? I found this, when I render wine glass and I have black area between glass and ground. There is little scene. Ofcourse final is when drops intersects in half of their valume, and I need good water effect. Thanks a lot. B.C.

kapky_help.hip

[anamous]

you're experiencing a combination of different issues. one of them is caustics, the other is ray bias.

since the drops completely cover the underlying surface, you need refractive caustics to have light reach the surface - otherwise it will shade as black since no light reaches it. to get caustics, you can either add a caustic light to your scene to precompute a caustic photon map, or set the mantra ROP to "All Paths" so that mantra traces caustic paths. i did the latter for simplicity.

the ray bias determines how much a ray origin is displaced before a trace ray is sent out to avoid having a microfacet or polygon trace itself. it should be adapted to the scene scale and amount of detail. in this case i set it to something ridiculously low, just to illustrate what it does.

cheers,

Abdelkareem

kapky_help.hip

[anim]

while All Paths or Caustics will give you more realistic result, they are usually very time consuming if you want good quality

so as an alternative you can simply exclude drops object from shadow casting

or if you are using Raytrace engine you can just set Faux Caustics on glass material to 1 1, this will not work on PBR however, that's why you need to use shadow mask while using PBR

[blackchicken]

Thats perfect, thanks a lot guys.

[blackchicken]

One little question, If I want to use custom whiteboards for reflections, A set constant material say color mult by 3, scene rendered with PBR is more lit. I remember that in Maya, mental ray, there is on/off use with irradiance. I cant find any of this settings im mantra. Ofcourse objects has unlinked from lights and shadows. Thanks

[hopbin9]

One little question, If I want to use custom whiteboards for reflections, A set constant material say color mult by 3, scene rendered with PBR is more lit. I remember that in Maya, mental ray, there is on/off use with irradiance. I cant find any of this settings im mantra. Ofcourse objects has unlinked from lights and shadows. Thanks

I don't use the constant shader. Try the Mantra Surface shader and use Emission with illuminates other objects turned off.

[dennis.albus]

while All Paths or Caustics will give you more realistic result, they are usually very time consuming if you want good quality

so as an alternative you can simply exclude drops object from shadow casting

or if you are using Raytrace engine you can just set Faux Caustics on glass material to 1 1, this will not work on PBR however, that's why you need to use shadow mask while using PBR

It actually does work in PBR, which is a huge timesaver in a lot of scenarios Just remember to switch on "Fresnel Blending" on your Mantra Surface Material. The nice thing is that you can even use a negative value for the "Min Shadow Intensity" to simulate the focusing of the light.

I don't use the constant shader. Try the Mantra Surface shader and use Emission with illuminates other objects turned off.

You could also use a Geometry Light and disable "Diffuse Contribution".

-dennis

Edited September 23, 2011 by dennis.weil

[NagyG]

Thanks for the suggestions.

I've used scaled sheets and gradient in the emission colour to make the centre a bit stronger.

Anyway I could not set nice the edge falloff of geometry light.

Edited September 25, 2011 by NagyG

[zarti]

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nice job there . i like it .

[Alexander Weide]

It actually does work in PBR, which is a huge timesaver in a lot of scenarios Just remember to switch on "Fresnel Blending" on your Mantra Surface Material. The nice thing is that you can even use a negative value for the "Min Shadow Intensity" to simulate the focusing of the light.

You could also use a Geometry Light and disable "Diffuse Contribution".

-dennis

pbr can be a time saver when you dont need a clean image. A image without noise is with pbr not possible in short time. And in Commericals there is no time for 1 hour Rendering on 1920x1080!if you got alot of layers with the short deadlines today you have to use raytrace or micropoly so you got similar results with rendertimes about 5 - 15 min a frame. noise in an image sux^^

bb

[dennis.albus]

pbr can be a time saver when you dont need a clean image. A image without noise is with pbr not possible in short time. And in Commericals there is no time for 1 hour Rendering on 1920x1080!if you got alot of layers with the short deadlines today you have to use raytrace or micropoly so you got similar results with rendertimes about 5 - 15 min a frame. noise in an image sux^^

bb

I was actually referring to faux caustics being a timesaver compared to photon mapped caustics

However, we almost always use PBR and are very satisfied with it's performance and quality. Especially in commercial work with lots of reflective surfaces and diffuse bounces PBR regularly outperforms the MP/RT engines. But there are also lots of other scenarios where I would choose MP in a heartbeat. Let's see what H12 brings to the table.

-dennis

Edited September 26, 2011 by dennis.weil