Quiestion about IOR values ....

yogeshwagh · July 31st, 2006

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 · August 2nd, 2006

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/VRay...ials_imap2.htm

Koper · August 2nd, 2006

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 · August 2nd, 2006

Quote:

Originally Posted by 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/VRay...ials_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 · August 3rd, 2006

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 · August 3rd, 2006

Quote:

Originally Posted by 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.

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-...-material.html

jkletzien · August 5th, 2006

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

http://www.glenbrook.k12.il.us/gbssc...ln/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_educat.../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 · August 5th, 2006

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 · August 6th, 2006

Quote:

Originally Posted by jkletzien

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

http://www.glenbrook.k12.il.us/gbssc...ln/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_educat.../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 · August 6th, 2006

Quote:

Originally Posted by 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.

thanks.. i am feeling great to hear from you,,,
and getting out me from confusion about the ior values.... thanks again

July 31st, 2006	#1 (permalink)
yogeshwagh Senior Member Join Date: Dec 2005 Location: India Posts: 109 Name: yogesh wagh	Quiestion about IOR values .... 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

August 2nd, 2006	#2 (permalink)
FlytE Veteran Member Join Date: Dec 2005 Location: Glasgow Posts: 575 Name: Andy Pennington	Re: Quiestion about IOR values .... 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/VRay...ials_imap2.htm

August 2nd, 2006	#3 (permalink)
Koper Veteran Member Join Date: Apr 2005 Location: The Hague, Holland Age: 26 Posts: 1,017 Name: AdriaaN van Jaarsveld	Re: Quiestion about IOR values .... 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

August 3rd, 2006	#5 (permalink)
Christopher Nichols Moderator Join Date: Apr 2002 Location: Lalaland Posts: 1,166 Name: Christopher Nichols	Re: Quiestion about IOR values .... 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. __________________ Christopher P Nichols

August 5th, 2006	#7 (permalink)
jkletzien Senior Member Join Date: Dec 2004 Location: Providence, RI Age: 40 Posts: 167 Name: jon kletzien	Re: Quiestion about IOR values .... I have been unsure of this territory for sometime myself but there is a law of reflection: http://www.glenbrook.k12.il.us/gbssc...ln/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_educat.../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. __________________ Jon Kletzien StudioAMD Inc. Website

August 5th, 2006	#8 (permalink)
Christopher Nichols Moderator Join Date: Apr 2002 Location: Lalaland Posts: 1,166 Name: Christopher Nichols	Re: Quiestion about IOR values .... 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. __________________ Christopher P Nichols

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode