Questions tagged [fresnel]

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3
votes
1answer
201 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 ...
2
votes
1answer
65 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
1answer
120 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 ...
8
votes
2answers
663 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-...
6
votes
2answers
724 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 ...
8
votes
0answers
716 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 ...
5
votes
1answer
139 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 ...
6
votes
1answer
505 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 ...
11
votes
3answers
942 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 ...
10
votes
2answers
1k 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 ...
17
votes
2answers
5k 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 ...