Questions tagged [lighting]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0 votes
1 answer
102 views

How does a path tracer capture light falloff if it deals exclusively with radiance?

My understanding is that path tracers deal with radiance because radiance is constant along a ray. You simply go through and evaluate the light transport equation: $$ L_o(p, \omega_o) = L_e(p,\...
Chris Gnam's user avatar
0 votes
0 answers
15 views

Different basis from spherical harmonics to represent light?

There's a lot of research being done in 3D shape analysis when it comes to PDE methods. Recently I've been reading quite a bit of literature on this subject and recent trends in this subject propose ...
user8469759's user avatar
1 vote
0 answers
167 views

Spherical Harmonics for view-dependent effects in research of learned radiance fields (NeRF, 3D Gaussian Splatting)

In research on making the rendering of learned radiance fields (e.g., neural radiance fields) faster, many approaches use Spherical Harmonics (SH) to approximate view-dependent color (e.g. baking SH ...
wawaderwaran's user avatar
2 votes
0 answers
52 views

Volumetric Renders become brighter as the focal length changes

Before we start, I have to warn yall, this program was written in VEX. Which is a programming language for Houdini. So it is a language within a 3D software. Its not really meant for this sort of ...
ErikHall's user avatar
  • 121
1 vote
0 answers
61 views

What is this cardioid/fish-like graphic that appears in FFXVI when looking at the sun?

In Final Fantasy 16, a recent video game, when looking towards the setting sun, one sees several circles, which seem like the lens flare that one commonly sees in games. But the most prominent (circle)...
chausies's user avatar
  • 111
0 votes
1 answer
102 views

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

I have the following code in python using the vedo package ...
Sarah V.P's user avatar
  • 101
1 vote
0 answers
49 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 ...
egil87's user avatar
  • 11
0 votes
1 answer
97 views

With a light source at (0,2,0) and unit cube (from [-1,1]) using a given shading formula, how is the r,g,b for each surface calculated?

The above problem is from a past Computer Graphics exam. I am particularly confused about the explanation given, firstly for the top and bottom planes (since the direction of normal for top plane ...
LC796's user avatar
  • 3
1 vote
0 answers
60 views

Normal Map Under rotation Issue

I have been trying to apply normal maps to a rotating sphere with light shining directing from above the sphere (0,1,0). but lighting does not look correct under rotation as one side of the sphere ...
Sina Dasht's user avatar
0 votes
0 answers
97 views

Ray light color at distance

I am obviously not understanding something related to light for a ray tracer. Reading Spectral representation and Point light calculation A bit of a context: My question is: in room at X degrees ...
LeXav's user avatar
  • 23
1 vote
0 answers
58 views

replace IBL with single color - the lighting equation

I want to avoid IBL (image based lighting), however my scenes are way too dark - especially close-to-mirror like surfaces, which get little contributions from other direct light sources in the scene. ...
Tomas's user avatar
  • 41
0 votes
1 answer
187 views

Blinn-Phong, GGX and half vector for light

I read a lot about lighting recently but I have (at least) one thing that remains a dark corner: The Blinn-Phong and this opengl sourcetalks about an halfway vector. My understanding: This vector is ...
LeXav's user avatar
  • 23
1 vote
1 answer
123 views

Can anyone summarize in simple terms, how PSSMLT/MLT algorithms work?

I understand backwards path tracing and bidirectional path tracing (BDPT). However I'm failing to understand how Metrpolis Light Transport methods are even remotely feasible to run. My understanding ...
Chris Gnam's user avatar
1 vote
0 answers
109 views

Directly Sampling an Area Light

So in my path tracer I sample both some bounce ray given an importance function for the current BRDF, and if applicable (reflection is non-specular) I directly sample all light sources (for my ...
Chris Gnam's user avatar
1 vote
0 answers
189 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
1 answer
81 views

Path tracing - colors/shadows sharper than they should be

Problem description When comparing Cornell Box image generated by my path tracer I noticed that colors are much more sharp/saturated (don't know specific term) than they should be. Comparison (on the ...
RafalMaziejuk's user avatar
2 votes
0 answers
37 views

How to add HemisphereLight to a simple threejs scene?

I'm trying to add light and see its changes in a simple scene in threejs but no matter the intensity or the color I set for the light, I see no change in a scene. Actually, if I don't include the ...
Jonas's user avatar
  • 31
1 vote
0 answers
150 views

MIS path tracing got darker image than brute force path tracing

I'm trying to implement the multiple importance sampling path tracing, the MIS path tracing uses the MIS to combine the direct light sampling and brdf sampling to evaluate the direct lighting. The ...
yys_c's user avatar
  • 11
1 vote
2 answers
278 views

Applying Phong illumination to a colored surface

The formula for Phong illumination as given on Wikipedia (see there for the variable definitions) is: $$I_\text{p} = k_\text{a} i_\text{a} + \sum_{m\;\in\;\text{lights}} (k_\text{d} (\hat{L}_m \cdot \...
jwodder's user avatar
  • 119
0 votes
0 answers
30 views

How to improve rendering of surface water in shaded-relief images

I asked a version of this question on GIS Stack Exchange three months ago, but did not receive an answer. So I am posting it here. I’ve written a simple Java application for rendering high-resolution ...
Gary Lucas's user avatar
0 votes
0 answers
96 views

Light brightness calculation

I've implemented the Phong shading model and I would like to improve the brightness depending to the distance of the light, its spectrum, luminosity and the cameras exposure time. Each of your light ...
Thomas's user avatar
  • 1,198
0 votes
1 answer
48 views

Understanding the diffuse component of light

I'm a little bit confused with the transition from just setting solid colors to object to involving light and its different components. For instance, the following formula $R = I K_d max(0, n.l)$ that ...
Essam's user avatar
  • 115
1 vote
0 answers
30 views

Distance to arbitrary set of line segments acceleration structure?

Background: I'm trying to render lightning within a volumetrically rendered cloud. I'm currently using a series of line-segments to represent lightning. At first I used a distance field rendered into ...
Krupip's user avatar
  • 280
2 votes
0 answers
182 views

physics/math of lighting gradient of a 3D object

Consider a monochrome ball. The colours of the pixels is a function of the point height, the light intensity, the light angle, and the surface material (reflection). What is the simplest formula ...
Googlebot's user avatar
  • 131
1 vote
1 answer
83 views

Using the Preetham/Shirley/Smits daylight model to get practical (s)RGB values

I have implemented Preetham, Shirley, and Smits’s daylight model using Aubrey Jaffer’s Scheme implementation as a reference and confirmed that my implementation produces the same results in the xyY ...
Daphne Preston-Kendal's user avatar
2 votes
1 answer
671 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 ...
Vít Gardoň's user avatar
1 vote
0 answers
285 views

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, ...
SupaKoopaTroopa64's user avatar
1 vote
0 answers
144 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 ...
Sam's user avatar
  • 164
3 votes
1 answer
318 views

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 ...
Metalian's user avatar
0 votes
1 answer
187 views

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 ...
Simon's user avatar
  • 163
1 vote
1 answer
191 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
1 vote
1 answer
71 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 ...
danding's user avatar
  • 25
1 vote
1 answer
85 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 ...
danding's user avatar
  • 25
3 votes
1 answer
371 views

Hard Shadows with Dielectrics/Transparency

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 ...
Paul Hübner's user avatar
0 votes
1 answer
701 views

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-...
Jonas De Schouwer's user avatar
0 votes
2 answers
265 views

Ambient occlusion depth buffer normalization

Been trying to follow a shader from A Comparative Study of Screen-Space Ambient Occlusion Methods http://frederikaalund.com/wp-content/uploads/2013/05/A-Comparative-Study-of-Screen-Space-Ambient-...
Boinking's user avatar
0 votes
1 answer
176 views

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 ...
mbl's user avatar
  • 291
0 votes
1 answer
84 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 ...
Vectorizer's user avatar
2 votes
1 answer
178 views

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 ...
BinaryGuy's user avatar
  • 123
1 vote
1 answer
107 views

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 ...
Noah Witherspoon's user avatar
1 vote
1 answer
253 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 ...
fakhir's user avatar
  • 131
1 vote
1 answer
89 views

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 ...
Peter's user avatar
  • 113
2 votes
0 answers
104 views

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. ...
MothRemovalInProgress's user avatar
0 votes
1 answer
58 views

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 ...
evilmandarine's user avatar
1 vote
0 answers
92 views

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(...
ali's user avatar
  • 730
0 votes
1 answer
111 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 ...
jackw11111's user avatar
4 votes
2 answers
246 views

"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 ...
AnnoyinC's user avatar
  • 312
0 votes
0 answers
41 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 ...
Radoshan's user avatar
3 votes
0 answers
168 views

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 ...
user1754322's user avatar
0 votes
1 answer
100 views

Problem sampling uniformly envmap with GGX

I have made a program that samples uniformly an environment map and computes the lighting using the GGX BRDF. I have made a small example that reproduces the issue I'm having. You can check it out ...
user1754322's user avatar