Questions tagged [lighting]

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0answers
28 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(...
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1answer
60 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 ...
3
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2answers
69 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 ...
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0answers
37 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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0answers
31 views

examples of perspective camera usage

A piece of text suggested that a weak perspective camera could be used for example to capture an airplane flying at a very high attitude but it cannot be used to capture let's say a tower when we are ...
3
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0answers
90 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 ...
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1answer
28 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 ...
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0answers
47 views

Can ambient light reflection of a surface be larger than diffuse reflection?

According to Phong's reflection model, there are different reflection constants (k) and different intensities of the light source (i) for ambient, diffuse, and specular terms: $I_p=k_ai_a+\sum_{m \in ...
2
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2answers
181 views

OpenGL - Recreate position in viewspace from depth values

Current state: I belive the reconstructed positions are correct. However, I still have the same problem as all the time. When I rotate around my single pointlight appears to be moving around also. I ...
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0answers
57 views

Calculating of vectors in Phong Lighting Model

I'm learning about computer graphics and I have some questions about calculation of the vectors, so I will write the exercises that I have and I hope that someone can help me with the formulas that I ...
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1answer
83 views

Raytracer help - Background color writing over some colors?

I'm implementing Peter Shirley's "Raytracer in a Weekend: The next week" and I'm having some trouble with rendering a scene with a light. I'm not sure if the issue is the background color or ...
4
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1answer
517 views

What is a vertex normal used for?

I'm new to the graphics area, and when it comes to the light part, the concept of vertex normals confuses me a lot. First, I cannot imagine how a vertex could have a normal, and second, when ...
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1answer
116 views

Prove radiance contributions of deeper paths fade away

When ray tracing, I find it intuitively clear that deeper paths have a lower contribution to the overal picture than shorter paths. This is the main reason why it is generally okay to render a picture ...
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0answers
78 views

Pdf division in BRDF sampling

While following scratchapixel's tutorial on indirect diffuse implementation in path tracing, the samples gets divided by the pdf, which in case of a uniform pdf results in $1/2\pi$ so we have that the ...
0
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1answer
62 views

Confusion about light PDF

I have a doubt regarding shape lights pdfs, specifically various sources point at the fact that the pdf is a constant: $$ lightpdf = 1/A $$ Where $A$ is the area of the light surface. Expressed in ...
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0answers
24 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) ...
2
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2answers
72 views

Techniques for making tesselated shapes appear smoother?

What are some common techniques for making the edges on a tesselated shape less apparent without increasing the amount of tesselation which is actually carried out? As an example, I followed along ...
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0answers
47 views

Formula for non area light BRDFs

I'm reading a graphics book and it talks about BRDFs being the ratio between differential outgoing radiance and differential irradiance. The formula it gives is f(l, v) = dL(v)/dE(l) Where l is the ...
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0answers
148 views

Why does Schlick's approximation contain a \$(1-\cos\theta)^5\$ term?

The approximation writes the reflection coefficient as$$R(\theta)=R_0+(1-R_0)(1-\cos\theta)^5,\,R_0=\left(\frac{n_1-n_2}{n_1+n_2}\right)^2.$$Why is the exponent 5? Schlick 1994 introduces this ...
2
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1answer
187 views

Rendering equation for spherical lights

I am currently implementing spherical lights in my DirectX game engine. I decided to build the shading formula from the classical rendering equation. Here is what I get: The simplifications show that ...
4
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0answers
103 views

Irradiance field approximation with black probes

I'm posting here after some time searching the Internet and reading presentations and papers, to find out the best options to solve the problem I have. I'm implementing irradiance field with ...
2
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1answer
265 views

Difference betwen Rendering Equation, Lighting model, Ray Tracing, Global Illumination and Shadows?

What is the difference between all these techniques? I know what a lightning model does, eg Phong, Flat, Gouraud. As far as I know both Ray Tracing and Global Illumination are just lighting models ...
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0answers
634 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 ...
1
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1answer
169 views

Roughness Value of (Close to) Zero in Physically Based Rendering

In my Direct Light Physically Based Renderer, when I set the roughness too low (ie. 0.0 or close) the specular reflection doesn't show, not even at high resolutions and at perfect angle with the ...
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2answers
206 views

Do I need a normal matrix if I calculate lighting in an objects space?

As a quick reminder, here is what normal matrix is and why do we need it. Now the question - if I take the light position and transform it into an object space than I don't need the normal matrix at ...
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1answer
131 views

Pseudo rounded cube in OpenGL

If I have a cube in OpenGL, how can I have it appear like rounded? I think it's too complicated to really have the cube rounded so is there any "light trick" to have something like this: The cubes ...
0
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1answer
69 views

Physically realistic received irradiance values given some BRDF?

I am trying to simulate the actual response of a camera given some object that is reflecting light. I've written a ray tracer, and have a BRDF that I need to use, and I have a camera sensitivity in ...
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0answers
41 views

Clarification about Phong lighting model

I've read some tutorials about Phong and Blinn lighting models and tried to implement a rendered myself. To my knowledge, the basic approach consists of the following steps: calculate the vector from ...
1
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1answer
203 views

Tone Mapping in a physically based rendering ray tracer

I'm implementing a pbr ray tracer. Let's say that I'm at the end of the process: for each pixel pi, I accumulated the radiance value in vector pi = (radR, radG, radB). At this point, these values are ...
4
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0answers
168 views

Pre-filtered environment map, deriving the equation

I'm reading through this article, and more specifically I'm trying to derive the equation that would explain the implementation the following shader (still in the same article): ...
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0answers
32 views

gradual transition of light intensity formula

Imagine I have an x value that ranges from 1-100. The light source is pointed at x=50. From points 35 to 65 I want intensity to be 1 At the ends (ie 1 and 100), intensity should be 0 What formula ...
3
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1answer
162 views

How does Next Event Estimation work with transformed lights?

I am relatively new to path tracing, and I am trying to implement next event estimation. I am following the Monte Carlo integral used to compute the direct illumination from an area light: $$\frac{1}{...
2
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1answer
99 views

how many watts are in the SPD of the color white?

Please help. I'm trying to implement a ray tracer, going by the PBRT book and got stuck on an issue that I fail to find the answer to. My scenes are made from objects and light sources. From that, I ...
2
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1answer
144 views

Why is cos(𝜃) in the denominator in the reflectance equation and in the numerator in the shading equation?

Background: I'm reading https://learnopengl.com/PBR to learn about PBR. In the theory slide (https://learnopengl.com/PBR/Theory), the author has the reflectant equation as The theta (the angle ...
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1answer
128 views

How to simulate a line laser diode?

I'm interested in simulating the way a laser line deforms when it strikes an object and runs along the surface of it. Which concepts would be involved? Is there any 3D modeling software out there that ...
5
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0answers
145 views

How to use Photometric Units with Rendering Equation?

So I was just reading up on how to create more Physically Based Lights and wandered into the realm of photometry. I read the paper "Moving FrostBite to PBR" and in it the author claims he decided to ...
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0answers
96 views

Specular/Diffuse light on an icosahedron opengl

I'm having a problem with my model here. I draw an icosahedron using GLUT, and the radius is set to 0.8. The info of the coordinates are listed below: (X and Z are calculated since our radius is 0.8) ...
3
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1answer
428 views

Iridescence/Thin-film interference integration as a layer

I'm trying to integrate the thin-film interference effect described in the paper "Belcour, L., & Barla, P. (2017). A practical extension to microfacet theory for the modeling of varying ...
2
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2answers
221 views

Physically Based Shading for Diffuse surfaces

So I am currently in the process of implementing Physically based Shading in my pathtracer using microfacet models and I'm quite stuck at comprehending light interaction with diffuse surfaces. First ...
3
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1answer
931 views

How is lighting done in Rasterization based pipeline?

So I wanted to know how do Game Engines like Unity3D and Unreal do lighting. I'm familiar with Ray-tracing, pathtracing based renderers etc. But not much with rasterization based engines. I do know a ...
3
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3answers
850 views

Why Diffuse Light use max(N · H, 0) instead of just letting it be negative?

In Cg tuts, Diffuse Section Surfaces that face away from the light will produce negative dot-product values, so the max(N · L, 0) in the equation ensures that these surfaces show no diffuse ...
2
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2answers
191 views

Ghosting in volumetric lighting

Does anyone know any method to remove ghosting in volumetric lighting? When light move it leaves trail behind, i would like to remove it. Volumetrics are Bart Wronski style (in frustum) with ...
0
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1answer
182 views

How does the Modified Phong Lighting Model from the Phong Lighting Model?

How does the Modified Phong lighting model also known as the Blinn-Phong differ from the Phong Lighting Model? How can I distinguish the two?
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1answer
195 views

What are the 3 types of light reflection from surfaces in the Phong Lighting Model?

Can someone please explain what are the 3 types of light reflection from surfaces in the Phong Lighting Model? Maybe possibly using a diagram to help me understand it better?
13
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4answers
3k views

For shader math, why should linear RGB keep the gamut of sRGB?

sRGB is often contrasted with "linear RGB." Images are stored on disk and passed to displays in sRGB, which is approximately perceptually uniform in intensity. Shader math is done in linear RGB, ...
14
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2answers
9k views

Why are normal maps blue and purple in color?

I am learning about normal mapping. I understood that RGB values are converted into XYZ, but my question is how is it converted and why is the normal map blue and purple in color?
6
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2answers
317 views

PBR missing rim darkening on non metallic rough surfaces

If you have a dielectric (non metallic) sphere with a large roughness value (say, 0.95), and put it in a lighting environment that has a constant onmidirectional lighting value (such as 0.5) Cook-...
3
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1answer
316 views

How to deal with light leaks?

I'm struggling with light leaking through meshes (especially thin ones) due to interpolation between probes located on the opposite sides of those. First approach I took was mapping all static ...
3
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4answers
313 views

How to access several textures from huge amount of textures in a shader?

I'm developing a light probe based GI solution and currently dealing with light leaks due to interpolation between probes located on opposite sides of the walls. I want to tackle the problem by ...
1
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1answer
67 views

Non-point lights

Is there a technique for implementing non-point lights (i.e. light that has actual physical dimensions)? I can't think of anything except than making a light source out of multiple point lights, but ...