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Questions tagged [specular]

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"Charlie" Sheen BRDF's directional albedo integrates to values higher than 1 at low roughnesses. Does this mean it is not energy conserving?

I am implementing the BRDF from the 2017 paper "Production Friendly Microfacet Sheen BRDF". This BRDF is modelled as a coat layer stacked on top of a base specular. In order to do so in an ...
avilapa's user avatar
  • 43
1 vote
1 answer
202 views

Confusion over Microfacet-based BRDFs and Normal Distribution Functions

Through reading various sources online, I've become a bit confused. I'll briefly outline what I think I do understand: My understanding is that microfacet-based BRDFs assume there is always a perfect ...
Chris Gnam's user avatar
0 votes
0 answers
63 views

Unable to compute fresnel reflections properly

I am implementing fresnel reflections for materials in my renderer. According to this source, here the look I should obtain when rendering a sphere over a grey background: I have two implementations. ...
StudenteChamp's user avatar
0 votes
1 answer
142 views

Does fresnel reflection make sense for metals?

I am implementing fresnel reflections for materials in my renderer. Does it make sense for metals? Here my implementation: ...
StudenteChamp's user avatar
0 votes
1 answer
645 views

What does GGX stand for?

Many render engines implement the microfacet model for rendering surfaces that are rough, metallic, and/or transparent, a concept first published in "A Reflectance Model for Computer Graphics&...
NullPointerException's user avatar
0 votes
1 answer
136 views

How can I transform the circular blinn-phong specular into a square shaped highlight?

I am creating a custom shading model in Unreal Engine and I would like to create a square shaped specular highlight, without changing the shape of the light itself. I tried following the approach ...
mbl's user avatar
  • 301
1 vote
0 answers
223 views

Calculation of reflection vector in Phong specular lighting

I wrote the following phong reflection model for ray tracing in Rust, but I am not sure about the calculation of a reflection vector for the specular reflection. ...
user48423's user avatar
1 vote
0 answers
82 views

Temporal reprojection of specular reflection - finding previous frame color

In specular reflection result depends on view vector from camera to point. Because of that, when doing temporal reprojection and reprojecting position of current fragment while camera is translating, ...
mdkdy's user avatar
  • 2,169
1 vote
1 answer
197 views

Specular reflection with different viewing direction where reflection direction and viewing direction coincide

Suppose $P_1$ and $P_2$ two different points on surface. And let $l$: be the light source direction, $n$: normal vector $r$: specular reflection direction $v$: viewing direction . In case 1 (at $P_1$...
S. M.'s user avatar
  • 211
2 votes
3 answers
1k views

PBR : Understanding the right part of Split sum integration of specular IBL

This is the website I am learning from. In the specular part of IBL this is the split sum approximation Now the left part of the equation I have asked in This post and I have understood everything ...
Sync it's user avatar
  • 179
0 votes
0 answers
27 views

Adding specular reflections to a ripple simulation

I am following the algorithm shown in this code here. Essentially there is a simple simulation of heights and then the difference in heights on the x and y axis respectively (sampling adjacent points) ...
CalebK's user avatar
  • 243
0 votes
1 answer
207 views

total internal reflection implementation in pbrt-v3

I've been implementing a path tracer, referring pbrt-v3. However, I'm a bit confused about its implementation. Code is here. It seems when we sample to do transmission, it tests if it meets a total ...
jinglei's user avatar
  • 293
0 votes
0 answers
74 views

Cook-Torrance Specular BRDF Artifact [duplicate]

I am currently experiencing a very obvious artifact that occurs when looking at objects on very grazing angles Here is a picture of the artifact: I noticed that the issue was coming from my ...
Brady Jessup's user avatar
1 vote
1 answer
400 views

Normal Artifacts On Grazing Angles

I am currently experiencing a very obvious artifact that occurs when looking at objects on very grazing angles Here is a picture of the artifact: I noticed that the issue was coming from my ...
Brady Jessup's user avatar
2 votes
1 answer
1k views

PBR and Specular Aliasing

I have been following LearnOpenGL.com's tutorials on PBR. Everything makes sense and I wrote up a shader for my physically based renderer. I noticed that the results look great, however all of my ...
Brady Jessup's user avatar
5 votes
1 answer
2k views

Phong and the Rendering Equation: What's with the cosine?

Ignoring emission and shadowing for simplicity, the rendering equation can be stripped down to: $$L(x, \, \vec \omega) = \int_{\Omega}{f_r(x, \, \vec \omega^\prime, \, \vec \omega) \, (\vec \omega^\...
David Kuri's user avatar
  • 2,293
1 vote
1 answer
516 views

Direct illumination, specular surfaces, and MIS

Multiple Importance Sampling (MIS) is a technique used by Veach's VCM technique to balance responses of different surfaces to different types of importance sampling for direct illumination. My ...
Paul Ferris's user avatar
1 vote
3 answers
384 views

Same specular lighting on both tris in a quad (for "low-poly" "flat shading" look)?

Here's an example of the flat shaded squares I want. But my squares are made of two triangles, and I'm getting flat shading of those triangles. In openGLES 3.1 (android), I'm turning off ...
hyperpallium's user avatar
2 votes
0 answers
477 views

How to simulate specular reflection in Light Tracing?

I am implementing light tracing from this website. The right wall on the below image is perfect mirror(specular reflection). Its BRDF returns zero that's why it's been rendered black. But how is it ...
ali's user avatar
  • 740
10 votes
4 answers
27k views

What is the difference between glossy and specular reflection?

What is the difference between glossy and specular reflection? What is their relations with BRDF?
chaosink's user avatar
  • 591
3 votes
0 answers
564 views

Problem with specular BRDF (Monte Carlo & Path Tracing)

Above on the left is my attempt and on the right is what I'm aiming for.As you can see my sphere with the specular brdf has a weird dark ring In my radiance function I am recursing through the ...
Aloof's user avatar
  • 31
1 vote
0 answers
211 views

Pathtracing specular reflections vs. specular highlights

In path-tracing, is a specular reflection model like Blinn-Phong useful? Is it more accurate to render a complete reflection dependent on the objects roughness?
Orange Mushroom's user avatar
3 votes
2 answers
2k views

Phong: Real-time rendering of Metal and Plastic Materials

Using a shader that works like Phong, what would be the difference between painted Metal and plastic? I seem to remember reading in books years ago, that I no longer have access to, the following: ...
Invariant's user avatar
  • 133
3 votes
1 answer
366 views

How to send shadow rays to window light source with glazing

For rendering an indoor scene where light source is skylight coming in through the window opening, one can consider the window polyline as the light source, with the sky distribution, in direct ...
ali's user avatar
  • 740
5 votes
1 answer
1k 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 ...
PeteUK's user avatar
  • 700
1 vote
1 answer
265 views

Specular exponent spectrum

I read the MTL specification for materials and noticed that the specular exponent Ns must be a scalar value instead of a spectrum. Would a specular exponent with three color channels (i.e. RGB, XYZ, .....
Matthias's user avatar
  • 1,074
4 votes
1 answer
1k views

How to handle specular highlights with reflection / total internal reflection in a ray tracer?

Let's say that I have a raytracer that is rendering a scene that includes a refractive object. When a ray hits the refractive object, I know that I can use the fresnel equation (Schlick's ...
Alan Wolfe's user avatar
  • 7,801
31 votes
2 answers
7k views

Path tracing the Cook-Torrance BRDF

-- Sorry for the long post, but I prefer to do that way because "Devil is in the details." :) I am writing a path tracer from the scratch and it is working nicely for perfectly diffuse (Lambertian) ...
user avatar
4 votes
1 answer
720 views

Normal vector in Phong Illumination Model should be normalized?

I'm studying Illumination subject these days and I was given a problem which asks to calculate the intensity using phong illumination model. I'm little bit confused whether I should calculate normal ...
Samitha Nanayakkara's user avatar
8 votes
4 answers
2k views

Should ideal specular multiply light colour with material colour?

Ideal specular reflection is like a perfect mirror. I'm looking at the code to SmallPt and see that one of the spheres has an ideal specular material: ...
PeteUK's user avatar
  • 700
2 votes
1 answer
446 views

Bug: Overly Sharp Highlights in PBR

I'm still working on my BRDF equations. Theoretically, all equations are correct, but the hilights are super sharp. I'm not sure if this is a result of me not using Image-Based Lighting (I currently ...
Karim Abdel Hamid's user avatar
3 votes
1 answer
807 views

How to create specular surface in Mitsuba Renderer

I am a newbie in computer graphics and I am trying to develop a special case of path tracing really slowly! But first: I came up studying the Mitsuba renderer and one of its uses in the so-called GDPT ...
Tarta's user avatar
  • 355
4 votes
1 answer
116 views

Data fitting SVBRDF with L-M

I am reading two shot svbrdf capture . I want to understand the data fitting. For example, I have my input image 3000x2000 pixels, and I divide it to create my source tiles of 192x192 pixels. The way ...
boykely's user avatar
  • 149
23 votes
2 answers
8k 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 ...
Julien Guertault's user avatar
2 votes
1 answer
718 views

phong equation of illumination specular component

I'm stuck on this question asking me to calculate the intensity of a pixel using Ray Tracing. It gives values such as $I_i$ but doesn't give any coordinates. I know for the diffuse component, $...
user2976568's user avatar
5 votes
1 answer
419 views

Should not specular reflection on a rough surface be similar to diffuse reflection?

Different BRDFs are usually used to compute diffuse and specular reflection. Some of the most often used include for example the Lambert BRDF for diffuse reflection and the Cook-Torrance BRDF for ...
wip's user avatar
  • 1,861
18 votes
2 answers
7k views

What is the accepted method of converting shininess to roughness, and vice versa?

Most modern renderers use physically-based materials and their models are often parameterized over roughness. Since this wasn't always the case with renderers, conventional assets often don't have a ...
ap_'s user avatar
  • 2,214
10 votes
1 answer
908 views

Trying to implement Microfacet BRDF but my result images are wrong

I am trying to implement microfacet BRDF model. I am reading Sebastien Lagarde's slides. I implemented formulas to my code but i think result image is wrong. Yellow is base color of material. ...
hmkum's user avatar
  • 131