Question About Realistic Renders

[tsiwt]

Hello

I was looking at the theory behind Physical Based Renders - and I read that everything apparently has Specular and everything has Fresnel.

When I dive into the database of materials provided by octane - I see that porcelain for example is made of diffuse and glossy. So how does this resemble real life?

I want to be able to create accurate materials - I read that you need to start with correct reflectance , then roughness, albedo color

But I am not sure this workflow translates to octane.

Does anyone here has a worflow of creating realistic materials based from research the materials online ?
Haven't found anything on this subject with regards to octane + C4d'

thank you.

[nuno1980]

Welcome to tsiwt. What's('are) your videocard(s)? Maximum how much time want you to render?


If you deserve "real life" then type of materials:
--> glossy materials
-mirror - diffuse 0.00; specular between 0.92 and 0.94; index of refraction 1.00; roughness 0.00; rest default
-metal - diffuse 0.00; specular 0.75; index of refraction 1.00; roughness 0.00 (if you want more roughness then increase to ~0.30); rest default
...

--> specular materials - all must have the dispersion (rainbow) because the industry can't remove "dispersion" in the glasses for eyes
-clear glass - reflection 1.00; transmission 1.00; index of refraction 1.509*; dispersion cofficient 0.006*; rest default
-orange glass (example) - reflection 1.00; transmission - RGB color [R 1.00, G 0.712, B 0.00] ; index of refraction 1.509*; dispersion cofficient 0.006*; rest default
-water at 25 ºC - reflection 1.00; transmission 0.9983; index of refraction 1.3244*; dispersion cofficient 0.002407*; rest default
...

NOTICE!!: in liveDB, most specular materials are bad settings, unfortunately except submitted by (I'm) Ricardo Rodrigues.

How do you set any material? - consult https://refractiveindex.info/ but I'm sorry for your bit complication

* - 2 formulas (convert from "abbe number" to "dispersion cofficient (= B)"; calculate from original refractive index (ior) to
ior dispersed):

Code: Select all

B = (n_d - 1)/V_d*((0.48613^2*0.65627^2)/(0.65627^2 - 0.48613^2))

F and C = F and C wavelengthes - If wavelength = 589.3 nm then should use F = 486.13 nm and C = 656.27 nm


n_d_dispersed = n_d_original - 10/3*B

B -> dispersion coefficient
n_d -> refractive index
V_d -> abbe number
n_d_dispersed - refractive index dispersed if the dispersion is enabled, for Octane Render software only

Good rendering!

[tsiwt]

Thank You Nuno1980


I am interested in the link you provided and the formula -

so basically for ethanol -

https://refractiveindex.info/?shelf=org ... age=Rheims

B =(1.3571 - 1) / 59.35 * ( .52365508707)

Reflection - 0.022956 ; refractive index - 1.357 ; dispersion coefficient 0.00315075411 ...

I am not sure how you get the RGB color and the transmission. ?


also I don't understand this part of the formula - F and C = F and C wavelengthes - If wavelength = 589.3 nm then should use F = 486.13 nm and C = 656.27 nm
what is this for?



If you had to do realistic porcelain how would yo go about it, I didn't find it in the link you provided.


thanks for all the help.

[nuno1980]

Thank You Nuno1980


If you had to do realistic porcelain how would yo go about it, I didn't find it in the link you provided.

I'm very sorry for confusion because I can't understand - you said "specular" (= reflection) in glossy material OR "specular" (material).

You choose to download any thing for porcelain (glossy material) in LiveDB but unfortunately, LiveDB isn't available on demo and you can buy Octane Render standalone.

I am interested in the link you provided and the formula -

so basically for ethanol -

https://refractiveindex.info/?shelf=org ... age=Rheims

B =(1.3571 - 1) / 59.35 * ( .52365508707)

Reflection - 0.022956 ; refractive index - 1.357 ; dispersion coefficient 0.00315075411 ...

I am not sure how you get the RGB color and the transmission. ?

"ethanol" specs at D = 589.3 nm (enter value of wavelength in micrometers in "refractiveindex.info" site - don't forget this SI (not nm)):
n_D - 1.3616
v_D - 59.35
transmission is same number to water (T = 0.9983)

I calculated 2 formulas...
B = (n_d - 1)/V_d*((0.48613^2*0.65627^2)/(0.65627^2 - 0.48613^2))
B = (1.3616 - 1)/59.35*((0.48613^2*0.65627^2)/(0.65627^2 - 0.48613^2))
B = 0.3616/59.35*((0.236322*0.43069)/(0.43069 - 0.23622))
B = 0.3616/59.35*(0.101738/0.19447)
B = 0.00609267*0.523155
--> B = 0.003187

n_d_dispersed = n_d_original - 10/3*B
n_d_dispersed = 1.3616 - 10/3*0.003187
--> n_d_dispersed = 1.351098

You can enter these results for specular material (ethanol) settings using Octane Render:
reflection - 1.00
transmission - 0.9983
index of refraction - 1.351098 (= n_dispersed)
dispersion coefficient - 0.003187 (= B)


Transmission - you can select "greysale color" or "RGB color" or...

also I don't understand this part of the formula - F and C = F and C wavelengthes - If wavelength = 589.3 nm then should use F = 486.13 nm and C = 656.27 nm
what is this for?

wavelengthes colors:
F - ultraviolet
C - infrared
D - yellow (visible light)

But you don't change any value of "F" nor of "C" in formula - look my calculations. I'm sorry.


Happy rendering!

[nuno1980]

!!UDPATE!!: I've edited 2nd and 4th posts about reflection for specular materials - I'm SORRY after I investigated water, glass... in real life but I stay the corrrect values of reflection for glossy materials.