Questions tagged [fresnel]

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2 votes
1 answer
262 views

BRDF sampling and evaluation of diffuse vs specular component

When I am sampling diffuse BRDF I am using cosine-weighted distribution and when I want to sample specular BRDF I use sampling by GGX distribution. I can decide how much light is reflected and how ...
0 votes
3 answers
551 views

Correct way to think about Fresnel effect

I am using Schlick approximation to calculate the value of the Fresnel effect I found here When I try to find corner cases for the formula I get the value of 1 when the angle between normal and ...
3 votes
1 answer
647 views

Iridescence/Thin-film interference integration as a layer

I'm trying to integrate the thin-film interference effect described in the paper "Belcour, L., & Barla, P. (2017). A practical extension to microfacet theory for the modeling of varying ...
  • 33
2 votes
1 answer
189 views

Confused on reflection coeffcient of Fresnel equations

I am reading a paper about layered materials. However, I am confused on the implementation of this paper. The following picture describe the layered material. r_ab is a complex reflection coeffcient ...
6 votes
1 answer
201 views

"Artist Friendly Metallic Fresnel" reversible?

While implementing the "Artist Friendly Metallic Fresnel" paper by Ole Gulbrandsen (http://jcgt.org/published/0003/04/03/paper.pdf), I read that it is fully reversible: (section 2.3.2): for all r,g ...
  • 138
9 votes
2 answers
1k views

Why is the half vector not used in diffuse BRDF Fresnel calculations?

I am currently working with Earl Hammon Jr's Presentation PBR Diffuse Lighting for GGX+Smith Microsurfaces (now mentioned as [PBR, p.XYZ] and have read through (among others) Brent Burley's Physically-...
  • 1,467
7 votes
2 answers
2k views

Fresnel equation with incident angle, n and k as input

I've seen a Fresnel equation for calculating the reflection amount at incidence angle with n and k values defined. This formula usually comes up in relation to computer graphics, but I can't find this ...
9 votes
1 answer
1k views

More accurate Fresnel approximation for a RGB-based Path Tracer

I'm writing a path tracer and, for the moment, spectra related data (spectral power distributions and spectral reflectance curves) are stored as RGB tuples. In the Cook-Torrance specular BRDF I am ...
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5 votes
1 answer
154 views

Equivalent of Fresnel law for determining transmitted/diffuse split

I understand that Fresnel tells us what percentage of light reflects vs refracts, but what law tells me the percentage of refracted light that is transmitted versus the percentage of refracted light ...
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5 votes
1 answer
915 views

Fresnel and specular colour

I'm trying to implement Cook-Torrance BRDF and had previously bookmarked this question as it looked very well thought out. Going through it, I'm confused about the Fresnel equation. The author has the ...
  • 700
13 votes
3 answers
1k views

What explains the high specularity of metals?

From my understanding, the specular color usually refers to the amount of light that is reflected when the surface is lit at normal incidence, and is noted $F_0$ or $R_0$. Moreover, for non metal ...
12 votes
2 answers
2k views

In a physically based BRDF, what vector should be used to compute the Fresnel coefficient?

The well known Schlick approximation of the Fresnel coefficient gives the equation: $F=F_0+(1 - F_0)(1 - cos(\theta))^5$ And $cos(\theta)$ is equal to the dot product of the surface normal vector ...
22 votes
2 answers
7k views

How to properly combine the diffuse and specular terms?

As far as I understand, in a BRDF the Fresnel term is telling us the probability for a photon to be reflected or refracted when it hits a surface. The reflected photons will contribute to the ...