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# Tag Info

## Hot answers tagged reflection

12 votes
Accepted

### Mirror Reflections: Ray Tracing or Rasterisation?

There are a couple of special cases where mirror-like reflections can be rendered efficiently using rasterization techniques, and these are commonly used in games, although they don't work for the ...
• 25.1k
8 votes
Accepted

### Choosing Reflection or Refraction in Path Tracing

TL;DR Yes, you can do it like that, you just have to divide the result by the probability of choosing the direction. Full Answer The topic of sampling in path tracers allowing materials with both ...
• 1,464
7 votes
Accepted

### Refraction in a Ray Tracer: What do with an intersection within the medium?

this is an interesting question (and I am actually an author on Scratchapixel so I can maybe help on that one)). Things go as follows: you cast the primary ray into the scene the ray hits the glass ...
• 656
7 votes

### What is the difference between glossy and specular reflection?

The charts you show aren't showing two different phenomena - "glossy reflection" and "specular reflection" - they're showing two parameters of specular reflection. One is the specularity or specular ...
• 6,840
6 votes
Accepted

### Fresnel equation with incident angle, n and k as input

@PaulHK's answer is correct I'm sure, here's a bit of a check to show that the IOR() function is calculating the reflection coefficients for $s$ and $p$ ...
• 330
5 votes

### Which technique should be used for rendering under water images, Ray tracing or Radiosity?

Radiosity is only efficient for diffuse to diffuse rendering. Path tracing is more versatile on the type of light transport that could be computed. The main issue with underwater rendering is the ...
5 votes
Accepted

### Tracing shadow rays in a scene with mirrors

It depends how you define easy and what kind of constraints you have. The general case of this is rendering caustics but that's probably not what you're looking for if real time is your target. If ...
• 1,585
5 votes

### Refraction in a Ray Tracer: What do with an intersection within the medium?

You need to spawn a new ray at each IOR interface. So let's say your ray hits the surface of the glass object. You spawn a new ray from the intersection point along the new IOR direction for air->...
• 2,322
4 votes

### Fresnel equation with incident angle, n and k as input

This is the complex number version of refraction, were K is the extinction coefficient. This is commonly used for metals. You can check the Wikipedia on refraction: Complex refractive index | ...
• 2,322
4 votes
Accepted

### How to choose which reflection probe to use?

Are you trying to make your own rendering engine? Here is a solution that prioritizes visual quality ; it is slightly more complex than the object-based solution you are referring to. For better ...
• 1,861
4 votes

### Strange sphere reflection effects in ray tracing project. I cannot figure out what causes them

The issue was caused by an incorrect calculation of the reflection direction vector. With D ray direction and N the normal vector: R = D - 2 * dot(D, N) * N The ...
4 votes
Accepted

### How does ray tracing handle the calculation of reflections and shadows in the presence of multiple translucent objects?

First off, I think the question is a bit vague. I'm not exactly sure what you really want so this answer is just based on my understanding of your question. Raytracing handles reflections and shadows ...
• 961
3 votes
Accepted

### Why are reflections in a spherical surface sharp, regardless of depth of field?

There's no visible blur for the same reason you often don't see blur in very wide angle lenses: the circle of confusion is much smaller than a pixel. But it is still there. An extreme example of this ...
• 1,585
3 votes
Accepted

### Why does Cubemap have 6 individual textures?

A texture is just a fancy lookup table; that's all it is. It's a function that you input some coordinate T into, which returns a value for that particular ...
• 9,842
3 votes

### Why does Cubemap have 6 individual textures?

Why starting from a 3D direction vector? Because that is most commonly the way you get the direction from the sight line where you want to sample the env map along. Technically you can use any convex ...
• 5,950
3 votes

### What is the difference between glossy and specular reflection?

Gloss and Specularity are features of the surface. In modern PBR terms we usually refer to the smoothness and metalness of a surface instead (unless you use a specular workflow, then metalness is ...
3 votes

### Mirror Reflections: Ray Tracing or Rasterisation?

You can mimic a mirror by masking out the visible reflective surface when you first render and then mirror the world around the reflective plane and render again while only drawing where the ...
• 5,950
3 votes

### Mirror Reflections: Ray Tracing or Rasterisation?

This is one of the most common "misconceptions" on rendering, rasterisation and ray-tracing. Don't get me wrong. This is a good question, but one that should be answered once and for all. So to ...
• 656
3 votes
Accepted

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

But, at this point, do i apply a specular highlight to the surface that i hit from the inside? Unless you have a light source inside your object, there's no point in doing lighting on the inside ...
• 1,585
3 votes
Accepted

### light spectrum reflection / absorbation?

When an object is illuminated by the sun, how does the reflected spectrum change? Does each surface has an own reflection spectrum? where each photon "checks" its wavelength and "...
• 1,196
3 votes

### How does Unreal Engine 5's Lumen (most likely) implement reflections?

Whether you use Lumen with hardware acceleration or not, Lumen is based on ray tracing. Software mode uses signed distance fields (SDF) to find intersections along a ray and so called cards to store ...
• 154
2 votes

### realtime dynamic reflections, which way to go?

If you want a real-time solution (no baking), and only need one reflection bounce, you can try to generate (or update) a cubemap of the scene every frame, as described in this graphics study of GTA5 ....
• 1,861
2 votes

### realtime dynamic reflections, which way to go?

If there is only a single flat mirrored surface the solution is to render the scene twices, once normally. Afterwards you use stencil to mark the area where the mirror is visible. Then only drawing ...
• 5,950
2 votes

### Which technique is fast to generate real-time reflections?

Usually modern game engines use Screen Space Reflections which is some kind of screen space raymarching. Basically, a simple way to achieve this is to shoot rays from the G-buffer. This means you use ...
• 176
2 votes
Accepted

### Expressing a reflected ray at a point as a function of the incoming ray and the normal to the surface at that point

$N \cdot L$ is the scalar length of the projection of $L$ on $N$ (assuming $|N|=1$). $(N \cdot L)N$ is the actual vector with the length of $N \cdot L$ in the direction of $N$. There is often a ...
• 25.1k
2 votes

### Finding all possible reflection matrices for a given Wythoff construction

I found an answer in the form of the Todd-Coxeter Algorithm from group theory. This still involves iterating over permutations of the group, and removing duplicates. However, the group can be defined ...
• 2,402
2 votes

### How does notch's new graphics engine work?

Notch's engine most likely works using volume raymarching in a volume field. This means that you shoot rays that move a certain distance and check whether they are inside and object or not. Once they ...
2 votes

### What to reproject when doing temporal filtering in stochastic screen space reflection?

Usual reprojection finds UV of current visible point into previous frame. For diffuse and rough objects it simply adds motion vector: ...
• 21
2 votes
Accepted

### Controlling "zoom" and "position" of a cubemap in shaders

Reflections based on a cubemap best represent a reflection at infinity. That is, since the only factor that a cubemap provides is direction, the cubemap acts as though it were at a distance from the ...
• 9,842
1 vote

### Why are reflections in a spherical surface sharp, regardless of depth of field?

Because the ball doesn't "see" the world through an imperfect lens system, whereas your camera in that case does. If you were to introduce an imperfect visual system around it, with a resulting ...
• 2,226

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