Questions tagged [specular]

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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 $P_1$...
2 votes
3 answers
381 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 ...
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0 votes
0 answers
26 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) ...
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0 votes
1 answer
187 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 ...
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0 votes
0 answers
72 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 ...
1 vote
0 answers
300 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 ...
2 votes
1 answer
793 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 ...
5 votes
1 answer
1k 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^\...
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1 vote
1 answer
415 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 ...
1 vote
3 answers
323 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 ...
2 votes
0 answers
413 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 ...
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8 votes
3 answers
23k 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?
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3 votes
0 answers
527 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 ...
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1 vote
0 answers
201 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?
3 votes
2 answers
1k 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: ...
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3 votes
1 answer
344 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 ...
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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 ...
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1 vote
1 answer
259 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, .....
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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 ...
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30 votes
2 answers
6k 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) ...
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4 votes
1 answer
581 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 ...
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: ...
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2 votes
1 answer
379 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 ...
3 votes
1 answer
635 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 ...
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3 votes
1 answer
112 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 ...
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 ...
2 votes
1 answer
666 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, $...
6 votes
1 answer
363 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 ...
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15 votes
2 answers
5k 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 ...
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9 votes
1 answer
856 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. ...
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