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  • #16
    Re: Variations of black

    make a new scene. create a plane. load in the default red plastic material thats in your material folder. change the RGB to almost pure black. assign it to the plane. GI will not affect this material no matter what the GI multiplier is set to. it is as though the material is like you stated "a black hole" it will absorb all the light and reflect none of it. Now, put the diffuse color to something in the gray's like 125 ish. re-render with the high multiplier and the scene will wash out.

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    • #17
      Re: Variations of black

      I think this might be exactly what you found in the other post you linked me too Micha.

      Multiplier of 1


      Multiplier of 10 (as you can see the ground plane has no change)



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      • #18
        Re: Variations of black

        now with a point light with a multiplier of 10.. When near all black it appears that the materials specular highlight values are lost.



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        • #19
          Re: Variations of black

          If you have your material very close to black (<15) then its never going to reflect or respond to any light, it just the nature of things being black. Thats why I suggested the filter color and not the diffuse. The filter color will make most things black, but spots that have a significantly sharper intensity won't get "sucked up" by the black of the material. One of may favorite sayings is a quote from Louis Kahn that my crit always says "If you want a dark room, then you have to put a small window of light to let people know how dark it is." Basically try to get the contrast on a "mostly dark" material rather then focus on getting it to be black. Besides, if you get a good contrast, then you can "darken" it with levels or in post.
          Damien Alomar<br />Generally Cool Dude

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          • #20
            Re: Variations of black

            make a new scene. create a plane. load in the default red plastic material thats in your material folder. change the RGB to almost pure black. assign it to the plane. GI will not affect this material no matter what the GI multiplier is set to. it is as though the material is like you stated "a black hole" it will absorb all the light and reflect none of it. Now, put the diffuse color to something in the gray's like 125 ish. re-render with the high multiplier and the scene will wash out.
            Hmm, I don't understand right, what the problem is. Grey material and homogen GI light cause a wash out look.

            When near all black it appears that the materials specular highlight values are lost.
            Here I'm not sure again. If you set a material black (0,0,0) than it mean, it stay black independent from the light source, because the diffuse light will be 100% absorbed. This is ok. Or did you mean, the reflections are influenced? This I can't see at the renderings.
            www.simulacrum.de - visualization for designer and architects

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            • #21
              Re: Variations of black

              I'm not sure if this is a hack or not, but I generally will just boost the IOR of my fresnel up a bit to get strength back in my reflections when making black reflective materials. But I'm not sure if thats physically correct or helpful in this situation.
              Best regards,
              Joe Bacigalupa
              Developer

              Chaos Group

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              • #22
                Re: Variations of black

                Are the reflections the problem or the diffuse color? If reflections are a problem, than I would disable all lights and set a reflection environment only. Than, a fresnel reflection is seted, the rendered image should show a reflection independent from the diffuse color.
                www.simulacrum.de - visualization for designer and architects

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                • #23
                  Re: Variations of black

                  All my reflections are almost completely mirrors or chrome or 100% or whatever you want to call it...either way the reflection strength is up there. Its hard to talk about "physically correct" when it comes to dark scenes/materials because our eyes adjust to things so much. This seems like more of a artsy kind of thing, so my inclination is the notion of "physically correct" could be thrown out the door...(unless you want to use a physical camera with a 10sec shutterspeed )
                  Damien Alomar<br />Generally Cool Dude

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                  • #24
                    Re: Variations of black

                    The ground plane material should be reflective and should be black, so it reflects the objects in the scene but it will not reflect light at all. i see what you're saying about the filter color, but i would be inclined to think that this is a glitch and not a mechanic of the application. if it was a mechanic of the app its the only render app that does this, and for what reason would you want it to do that? the object should be able to be RGB 0 and still be able to be specular. the values in this test render are not 0 either, i belive they are around 10 to 12. Even at 10 to 12 that is still no black hole black, so thats what i dont get. If it was a mechanic then i can see RGB 0 functioning this way, but apparently theres a threshold value that is unknown to man and undocumented.










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                    • #25
                      Re: Variations of black

                      Originally posted by Micha
                      Are the reflections the problem or the diffuse color? If reflections are a problem, than I would disable all lights and set a reflection environment only. Than, a fresnel reflection is seted, the rendered image should show a reflection independent from the diffuse color.
                      hey micha, its the light reflections, not the object reflections that is not working for me. the closer objects move to black the more they lose their specular highlights, or direct light reflections.

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                      • #26
                        Re: Variations of black

                        So, I was thinking. What if the reason why the black colors in Vray get "sucked up" is because of how it handles darkness, or in other words early termination. The idea behind early termination is great: basically dark areas (ie shadows and darker materials) can deal with less sampling, and this is a great way to cut down on "unnecessary" calculations and make rendering faster. But in this instance, we want that extra information because it may help bring out more details into our black materials. So what if we tell vray that we want to make the calculation more accurate. Maybe by adjusting some of the QMC Sampler parameters we can do this. Here's what I suggest: Adaptive amount=.65-.45, Noise threshold= <.005, min samples= >12. It may kill render times ;D, but who knows. I'll try it overnight and see if there is any difference and if this might be a good way to do darker scenes.
                        Damien Alomar<br />Generally Cool Dude

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                        • #27
                          Re: Variations of black

                          Originally posted by Travis Serio
                          Originally posted by Micha
                          Are the reflections the problem or the diffuse color? If reflections are a problem, than I would disable all lights and set a reflection environment only. Than, a fresnel reflection is seted, the rendered image should show a reflection independent from the diffuse color.
                          hey micha, its the light reflections, not the object reflections that is not working for me. the closer objects move to black the more they lose their specular highlights, or direct light reflections.
                          Good, now I understand. I would say it is a bug. The clear finish (fresnel) of a material should be totaly independent from the diffuse layer color. So it works in the real world.

                          I test it at the last r4 beta: it works fine here, no bug. The same at R3. If you like to see a highlight of a light, than you must set a glossienes below 1, because a point/light is infinite small and only a little blur make it visible.

                          Joe, if I set a radius for a point light, should this point light not be visible at surfaces with glossieness 1 too? Could somebody test it at 3ds max? Logical it should work so.
                          www.simulacrum.de - visualization for designer and architects

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                          • #28
                            Re: Variations of black

                            Originally posted by Micha
                            I test it at the last r4 beta: it works fine here, no bug. The same at R3. If you like to see a highlight of a light, than you must set a glossienes below 1, because a point/light is infinite small and only a little blur make it visible.

                            Joe, if I set a radius for a point light, should this point light not be visible at surfaces with glossieness 1 too? Could somebody test it at 3ds max? Logical it should work so.
                            If Travis was using the default plastic it has a highlight gloss of 1.0 - so that is probably why there is no highlight visible.

                            What radius are you talking about - shadow radius?
                            Best regards,
                            Joe Bacigalupa
                            Developer

                            Chaos Group

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                            • #29
                              Re: Variations of black

                              Yes, if the light source get a radius, than this radius shoud be shown at the highlights. And the glossieness would deteminate the blurieness of the "reflected" disk. At the moment, all lightsources of a scene show the same highlight independent from the radius of the light source. Maybe this is not implemented at Vray yet, but I think, so should it work.
                              www.simulacrum.de - visualization for designer and architects

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                              • #30
                                Re: Variations of black

                                Originally posted by Micha
                                Yes, if the light source get a radius, than this radius shoud be shown at the highlights. And the glossieness would deteminate the blurieness of the "reflected" disk. At the moment, all lightsources of a scene show the same highlight independent from the radius of the light source. Maybe this is not implemented at Vray yet, but I think, so should it work.
                                I was under the impression that the shadow radius had to do with soft-shadows - I'm not sure how that plays into highlights?
                                Best regards,
                                Joe Bacigalupa
                                Developer

                                Chaos Group

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