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# Questions tagged [reflection]

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### Choosing Reflection or Refraction in Path Tracing

I am trying to implement refraction and transmission in my path tracer and I'm a bit unsure on how to implement it. First, some background: When light hits a surface, a portion of it will reflect, ...
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12k views

Radiosity is basically what allows this: In a tutorial of Cornell University about Radiosity it is mentioned that: A ray-traced version of the image shows only the light reaching the viewer by ...
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358 views

### Polarising reflection and refraction for a wrap around water surface

I want to render realistic images of water in an orbiting space habitat. The image does not need to be generated in real time, although I wouldn't want it to take weeks either. I'm looking for an ...
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?
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### 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 ...
7k views

### Mirror Reflections: Ray Tracing or Rasterisation?

Are mirror-like reflections in computer graphics purely handled with ray-tracing/ray-casting techniques or are there some situations where they are achieved through rasterisation?
• 115
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### realtime dynamic reflections, which way to go?

I'm working on my own engine and I'm struggling to find any techniques that give okay-ish reflections in realtime on dynamic scene. So far the only technique I found that work in real time on dynamic ...
• 363
198 views

### fix over exposure in importance sampling in screen space reflections

I am having my first encounter with the rendering of indirect reflections in the form of screen space reflections in a game engine, but i am struggling to get correct looking results. (patterns arise ...
4k views

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

I am currently following a tutorial at Scratchapixel.com on refraction Here is the refract function: ...
• 2,511
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 ...
• 1,861
691 views

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

I have multiple reflection cube map that's prebaked before a scene. However I am being confused as to which one to choose. I am told I need to choose "closest cube map" then use it. However it is ...
• 321
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 ...
• 7,801
567 views

### Normal mapping for planar reflections

Ok guys, tricky one! I'm trying to modify this Unity script + shader to include normal mapping. The tl;dr is, it uses a single texture rather than a cubemap as it is only for reflecting in a planar ...
• 2,402
366 views

### Can raytracing be used to imitate the behavior of light to a higher degree?

Raytracing "sees" the pixel on the other side of the screen; but doesn't this mean the rays traced can be computationally reflected and refracted imitating the properties of actual light? It'd be ...
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697 views

### Tracing shadow rays in a scene with mirrors

In my real time ray tracer, I shoot primary rays from the eye, and at hit points, I trace to a single light source to determine if the object is shadowed or lit. Pretty straightforward stuff so far. ...
• 270
940 views

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

I am in the middle of implementing stochastic screen space reflection based on frostbite presentation here. On page number 39, it is stated that we need to reproject the ray intersection location ...
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### Expressing a reflected ray at a point as a function of the incoming ray and the normal to the surface at that point

Said L the incoming ray (at a point $P$). $R$ is the reflected ray. $N$ is the normal to the surface at the point $P$. $\alpha$ is the angle between $N$ and $L$ (and $N$ and $R$ also). It is assumed ...
• 321
117 views

### How can i achieve reflections like this?

I was in my elevator when i saw this... As you can see here that reflections are kind of stretched. What causes this? And how can we achieve something like this in computer graphics?
116 views

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

A question has come up recently in Blender SE, remarking on the absence of blur due to depth of field in reflections in a spherical surface. This is a real-life effect.. can anyone come up with a nice ...
• 123
464 views

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

I started a ray tracing project in Python. I made a CUDA kernel and a trace() function for each pixel. It works perfectly when calculating intersections, shadows and lambert shading, however when I ...
409 views

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

In this YouTube video, the creator mentions that reflections in Unreal Engine 5's Lumen "work by tracing the path of light as it bounces off of surfaces in the game world." Does this mean ...
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### Controlling "zoom" and "position" of a cubemap in shaders

I am trying to mimic reflections in image composition using shaders. I have gotten this far: In this image the floor is "reflecting" the back wall, however the reflection is uncanny because the ...
• 1,726
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### Fresnel and light reflection/refraction

I keep reading about fresnel and there is one thing I don't fully understand. My understanding : Here is my understanding so far, so please correct me where I am wrong. Fresnel is related to ior (eta)...
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592 views

### Calculating intensities of Virtual Point Lights in Instant Radiosity from IES lights

Short introduction I created a function that interpolates the IES luminious intensities (candelas) using Hermite interpolation, so in my code all light sources have $I(\theta, \phi)$ function - but ...
1 vote
583 views

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

@notch has recently been posting on an engine he is developing. He claims that it is voxel-based and supports deformable terrain, with a render distance of almost 1000 000 voxels and real-time ...
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1 vote
94 views

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

As a pet project, I'm trying to build a small app that visualizes 4D polytopes. I want to use the Wythoff Construction method, where the shape is generated kaleidoscopically by the interaction of 4 ...
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1 vote
1k views

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

I want to know about some technique with which i can generate nice reflections on the surface. I know one conventional technique where we invert an object and render it and blend it with the floor but ...
1 vote
452 views

### Understanding material .mtl files

I am reading this piece of documentation to understand mtl files So far I am stuck trying to understand the difference between ambient, diffuse and specular reflectivity (Ka, Kd, Ks). If I am ...
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1 vote
50 views

### BlinnPhong sphere edges look worse than Phong. Am I doing it wrong? (code and pictures included)

First of all, I am completely new to this so please excuse me if this is a dumb question. I am following the book Real-Time 3D Rendering with DirectX and HLSL, for now implementing shaders in Nvidia ...
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1 vote
213 views

### Normal mapping should affect specular reflections?

I'm asking this question on behalf of a friend so can't provide any images for now. The problem is to simulate a car paint material with some flakes or graininess in it. This is first done in blender ...
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1 vote
58 views

### Why Screen Space effects flicker?

Nowadays is less of an issue, i think SS got massaged a little bit, but you can still spot it. These happen with SS Reflections, SSAO and Bloom. When you move the camera, the effect starts to flciker ...
1 vote
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?
515 views

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

Rendering is the process of computing a three-dimensional geometric description of a scene into a two-dimensional image representation that looks real. Ray-tracing and Radiosity are two of the most ...
84 views

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

Raytracing can handle the interaction between light and multiple translucent objects in a scene by using global illumination and raytracing with volumetric effects to calculate the color of the object ...
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### light spectrum reflection / absorbation?

I would like to know how material works with respect to light. first of all, I've a lightsource e.g. the sun. The sun has a spectrum like figure1 Figure1 When an object is illuminated by the sun, how ...
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604 views

### Converting from RGB Color Picker to Surface Reflectance

I am trying to derive the material reflectance values from a color picker tool(say MS Paint). My understanding is to first gamma decode(raise to the power of 2.2) the RGB values from the color picker, ...
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208 views

For a Lambertian surface, the radiance at a point is $$L = \frac{\alpha}{\pi}\cos\theta_i E_0$$ If we have an infinite flat surface, albedo = 1, illuminated directly normal, then we get L = \...
• 103
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### 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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46 views

### Understanding the BRDF Equation

I am studying the BRDF equation. From Wikipedia, the equation is as follows: I have one main question: Where does the $\cos{\theta_i}$ in the denominator come from? The denominator implies that \$...
116 views

### How to pick values of ambient, diffuse, specular for Phong Lighting?

I have the following code in python using the vedo package ...
63 views

### Realistic chainmail reflections for videogames

If I were to create a chainmail that has realistic reflections, where would I start learning about what mechanisms to use? Normal cloth seems too simple, and the reflections look bad (they have to be ...
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### Wrong reflection

Here is a youtube video showing my problem: youtube.com/watch?v=y8J7VhS2pkM I think I'm either doing the texture lookup on the reflection texture wrong, or the reflection or view matrix is somehow ...
2k views

### Color shading and light calculation for ray tracing

I am currently building a ray tracer and I came across a problem and confusion regarding the light calculations. For lighting, I am using the following mathematical model: Where ...
558 views

### Ray tracing in One weeked: issue with metal reflection

Problem I am following the book Ray tracing in one weekend , and I got stuck after the implementation of the material Metal. I checked my code many times, and it looks exactly like the code ...
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