# Questions tagged [lighting]

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25 views

### Rendering equation - brdf / pdf > 1?

I am creating a path tracer and I got some strange results when calculating the strength of light. I am using a rendering equation inspired by this diagram: When I use the cosine everything gets ...
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### How are point and pure directional lights sampled in an unbiased path tracer?

To perform importance sampling on a light source, a probability density function must be provided for the sampling distribution. For most light sources, a valid probability distribution can be found, ...
48 views

### Are virtual point lights in many-light global illumination the same light probes?

There are several papers like this one here that refer to a concept called many-light global illumination using Virtual Point Lights (VPL). That is, the problem of global illumination is reduced to a ...
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### Next Event Estimation for Triangle-based Light Sources

I have a question regarding the NEE for light sources that are composed from triangles. I implemented the next event estimation (explicit light source sampling) for spherical light sources but after ...
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### OpenGL old-style diffuse shading producing unexpected effects

Question: What is going wrong with the shape of the contours of constant illumination in the below picture ? Detail: Although Lambertian shading might be ill-regarded because it exposes the hard edges ...
105 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 $P_1$...
37 views

### [Subsurface Scattering]What's the meaning of diffuse coefficient Rd in bssrdf

Recently, i am reading the papaer A Practical Model for Subsurface Light Transport . I have understand the radiative transport equation : and the approximation of the diffusion equation: . In BRDF ...
43 views

### [Subsurface Scattering]Reflection from Layered Surfaces due to Subsurface Scattering

Recently, I am doing some research about subsurface scattering. i am a little confused about the backscattered radiance mentioned in this paper Reflection from Layered Surfaces due to Subsurface ...
56 views

I am writing a raytracer which is meant to support shadows. Previously, I have naively implemented hard shadows by casting a shadow ray towards the light (+ offset) and seeing if it hits anything ...
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### What is meant by ‘NEE’ in computer graphics?

I am reading this paper [Practical Path Guiding for Efficient Light-Transport Simulation, Müller et al, 2017] and it contains the following sentence: In practice, however, we recommend combining path-...
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### Trying to understand how to render a volumetric point light

My goal is to render a volumetric point light as explained in this book's chapter 10: FGED Rendering The book explains the math pretty well, but I'm not sure I understand what is the required setup ...
56 views

### Motivation behind tesselation

This question is NOT about the hardware difficulties and shortcomings of tesselation shaders I am trying to understand the motivation behind tesselation shaders. Why/when/where tesselation is a good ...
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### Techniques to implement a glow that encompasses a volume

I have an old renderer from years ago written with OpenGL immediate mode. I've decided to learn Vulkan and I'm converting my old project as a way to learn the new concepts. One of the things my old ...
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### Area-light approximation in 2D

I’m trying to render a 2D image something like this: …where an arbitrary shape has its border illuminated by a line in a relatively physically accurate way, i.e. with less illumination reaching the ...
71 views

### Ray tracing Bug with Diffuse material

I am trying to do ray tracing in python (following the tutorial given in Ray Tracing in a weekend). Basically I am shooting rays from eye and the recursively bounce around, each time they hit ...
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### Is spectral response curve and spectral power distribution the same thing?

I'm reading section 5.2 of pbrt 3rd edition and came across the part where they explain the concept of RGB colors. When we display an RGB color on a display, the spectrum that is actually displayed ...
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### Why do materials have both an ambient color and a diffuse color?

One of the first things I learned about computer graphics lighting (and light in general) is that when a ray of light hits a surface, the surface absorbs certain colors and the light retains the rest. ...
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### How's this laser cutting effect with backlight achieved?

Sorry for the general question, I don't even know how to tag it: https://www.youtube.com/watch?v=61UkkpsASwQ In this video, the effect is such as if there were a laser cutting a shape with a light ...
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### How to use IES Light Profile with an area light source?

I want to use IES profile with an area light. My understanding is that the IES file assume the source to be a point light. That is in case of (large)area light the measurements are taken at a distance(...
82 views

### What effects are used to light this scene?

I am interested how that image on the right of the slider (just albedo) can produce such a realistic looking scene as the scene on the left. What effects (at a minimum) does this scene seem to be ...
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### "whiteness" in center of bright colored lights - what is it called?

When a source of colored light is very bright, it's center appears white. What is the term I need to look for so I can implement this in my shader? I have added an image which is an example of what I ...
39 views

### I am trying to find a clip about the art of old computer graphics

I have saw a clip where a guy talked about the art of squeezing some nice graphics into a very small space that was available on old computers. Come to think of it, it sounded something like today's ...
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### IBL looks too dark with uniform sampling

I'm making a program that illuminates a sphere using an environment map. For each fragment in the sphere, I compute a many random directions in the hemisphere along the surface normal (no importance ...