Quiestion about IOR values ....

[yogeshwagh]

hi to all,

i want a help on Vray IOR values for reflection. I have a Factory scene to render. and almost all the objects in my scence are having the Falloff Type of reflection.

I have given by default IOR values ahich are 1.6 for all reflectiv materials. now my image takes 2 hours to render with 4 passes high type of animation settings and all object are closer to the camera.

My image size is 1920 X 1080 Pixels. now my quiestion is about the rendertime. i have to reduce the rendertime to near about 40 mins per frame without calculation of irradiance map. if i reduce the IOR values in the range of 0.5 to 1 will it be work for rendetime and calculations for irradiance map.

please help about it........

 

 

Thanks

Yogesh

[FlytE]

It may reduce your rendertime if your reflections are not as strong, but I wouldnt think it would be by much. I would look at other things like glossies and if you arent already doing it try creating your irradiance map seperately so you dont have to calculate it for every frame. Heres a useful tut:

 

http://www.spot3d.com/vray/help/VRayHelp150beta/tutorials_imap2.htm

[Koper]

to my knowladge IOR is how much ligth is displaced when being reflected or passed through an object. typical Glass has an ior somewhere between 1.5 and 1.62 (i think). Reducing the ior settings on any renderer will improve the rendering time but will the objects look the same? o don't think so

[yogeshwagh]

It may reduce your rendertime if your reflections are not as strong, but I wouldnt think it would be by much. I would look at other things like glossies and if you arent already doing it try creating your irradiance map seperately so you dont have to calculate it for every frame. Heres a useful tut:

 

http://www.spot3d.com/vray/help/VRayHelp150beta/tutorials_imap2.htm

 

 

thank you very much, i want some help from you sir, i want gray alluminuim material to all my objects in my scene. so can u please help me about how to create this type of material.

 

 

Thanks

Yogesh

[Christopher Nichols]

IOR is an index of how much the light is distorted as it refract through the surface. However, it is not tied to simply transparent objects. Metals have IOR as well, because it is also related to when a surface stops obsorbing the light and starts to reflect it (specularly). This is known as done via the Fresnel which is related to the IOR. An IOR of 1 means no distortion. technically you can't get an IOR less than 1.0 in the real world.

[yogeshwagh]

IOR is an index of how much the light is distorted as it refract through the surface. However, it is not tied to simply transparent objects. Metals have IOR as well, because it is also related to when a surface stops obsorbing the light and starts to reflect it (specularly). This is known as done via the Fresnel which is related to the IOR. An IOR of 1 means no distortion. technically you can't get an IOR less than 1.0 in the real world.

 

hi ,

thank you very much chris. its great to get reply from you:), actually i think 1.6 Index of reflection value is an greater value which is used only for mirror like materials.

for image please refer my another thred on to create the aluminum materials.

thanks a lot for your valuable reply

 

http://www.cgarchitect.com/vb/18471-want-some-help-create-grey-alluminium-material.html

[jkletzien]

I have been unsure of this territory for sometime myself but there is a law of reflection:

 

http://www.glenbrook.k12.il.us/gbssci/phys/Class/refln/u13l1c.html

 

So my understanding like others here is that IOR in VRay has nothing to do with reflections. And before I seem like a total idiot to all, I thought that anisotropic and glossy phenomena are just the implementation of the law of reflection over a surface that is perturbed/rough at a finer or even molecular level.

 

http://www.neilblevins.com/cg_education/aniso_ref/aniso_ref.htm

 

Anyway that doesn't answer the render time question but that is one art school grad's (ie. I know nothing but I have student loans) understanding about the relationship between IOR and reflection.

 

As far as their values it would be an interesting test to see if the computer multiplying by 1.6 is as fast as 1.0. I would also be stunned like Flyte if in fact turning down the intensity of the reflection made the render times less.

 

I think that the correct answer is Flyte's suggestion to look into the amount of glossy reflections and do the animation tutorial. But I am pretty darn sure that making your mirror an IOR of 1.6 won't do anything.

[Christopher Nichols]

Since IOR stands for Index of REFRACTION... it does not have anything to do with reflection (directly). But reflection and refraction go hand in hand via fresnel, which measures at what angle of incidence an object stops obsorbing light and starts to reflect it. And that angle is directly relacted to the IOR value.

[yogeshwagh]

I have been unsure of this territory for sometime myself but there is a law of reflection:

 

http://www.glenbrook.k12.il.us/gbssci/phys/Class/refln/u13l1c.html

 

So my understanding like others here is that IOR in VRay has nothing to do with reflections. And before I seem like a total idiot to all, I thought that anisotropic and glossy phenomena are just the implementation of the law of reflection over a surface that is perturbed/rough at a finer or even molecular level.

 

http://www.neilblevins.com/cg_education/aniso_ref/aniso_ref.htm

 

Anyway that doesn't answer the render time question but that is one art school grad's (ie. I know nothing but I have student loans) understanding about the relationship between IOR and reflection.

 

As far as their values it would be an interesting test to see if the computer multiplying by 1.6 is as fast as 1.0. I would also be stunned like Flyte if in fact turning down the intensity of the reflection made the render times less.

 

I think that the correct answer is Flyte's suggestion to look into the amount of glossy reflections and do the animation tutorial. But I am pretty darn sure that making your mirror an IOR of 1.6 won't do anything.

 

ok, thanks for helping me about the IOR . and getting out me from confusion about the ior values.... thanks again

[yogeshwagh]

Since IOR stands for Index of REFRACTION... it does not have anything to do with reflection (directly). But reflection and refraction go hand in hand via fresnel, which measures at what angle of incidence an object stops obsorbing light and starts to reflect it. And that angle is directly relacted to the IOR value.

 

thanks.. i am feeling great to hear from you,,,

and getting out me from confusion about the ior values.... thanks again:D

[jkletzien]

The conservation of energy, and the ratio of reflected to absorbed light aside, I still am having a hard time understanding if yogeshwagh is adjusting the VRay fresnel reflection value, or the IOR value.

 

in determining the dimunition of reflections on a material as Christopher has described on his post - you can adjust the fresnel value which will do exactly as he descibes (though I prefer the old school use the fall off map in the reflection slot - as I believe Christopher does in his video, which you should get if you don't have it)

 

In any case at least we're all in agreement that IOR in VRay isn't going to affect your reflections- the fresnel value will, though for a mirror there is no discernable fresnel effect - but in VRay these two are completely independent of each other regardless of how it is in the real world - where Christopher is absolutely correct.