# Questions tagged [lighting]

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23 votes
2 answers
10k views

### How is a light probe different than an environmental cube map?

Looking at a light probe texture, it looks like a blurry environment map. What's the difference between the two, how is a light probe made, and what is the benefit of it being blurry?
• 7,351
18 votes
2 answers
15k 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?
17 votes
3 answers
11k views

### What are Spherical Harmonics & Light Probes?

What are Spherical Harmonics & Light Probes? How useful are they in computer graphics? What exactly do they do? I've heard the word spherical harmonics & Light Probes everywhere, from siggraph ...
• 2,423
14 votes
2 answers
12k views

### How to Calculate Surface Normals for Generated Geometry

I have a class that generates a 3D shape based on inputs from the calling code. The inputs are things like length, depth, arc, etc. My code generates the geometry perfectly, however I am running into ...
• 243
14 votes
2 answers
2k views

### How to build a decent lens/camera objective model for path tracing?

I have written a small path-tracer after learning and experimenting on smallpt. The only thing that I did not write (and understood) myself is how the initial rays are computed and fired from the ...
13 votes
4 answers
5k 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, ...
• 275
11 votes
2 answers
8k views

### What is ambient lighting?

Wikipedia says: An ambient light source represents a fixed-intensity and fixed-color light source that affects all objects in the scene equally. By saying "affects all objects equally" they mean ...
• 587
11 votes
2 answers
2k views

### How is screen space ambient occlusion implemented?

I do not understand the explanation from wikipedia. For every pixel on the screen, the pixel shader samples the depth values around the current pixel and tries to compute the amount of occlusion ...
• 587
10 votes
2 answers
3k views

### Rendering equation - why unsolvable directly?

Why is the rendering equation, introduced by Kajiya in 1986, not solvable directly/analytically?
• 109
10 votes
1 answer
2k views

### Efficient rendering with many light sources

To render a scene with a single light source using phong shading, one can calculate the final color of each fragment passed into the fragment shader based on the ambient/diffuse/specular components of ...
• 403
9 votes
1 answer
3k views

### OpenGL specular shading - Gradient banding issues

I use Phong shading as my lighting model. Nevertheless, the specular shading produces gradients in the light cone: Hopefully you can see the gradient starting from the lower left corner expanding ...
• 591
9 votes
1 answer
687 views

### Tweaking a glow shader to make it look better

I have a simple game and and subjects of it are these little lines. It is targeted for iOS and android so it has a HUGE range of processors that it could run on, right now. I am trying to add ...
• 1,365
9 votes
1 answer
2k views

### What is "Object Space Lighting"?

Looking at Star Swarm, a demo for the Nitrous engine, I found this little line: "Nitrous uses Object Space Lighting, the same techniques used in film, including real-time film-quality motion blur." I ...
9 votes
2 answers
1k views

### How is spectral rendering handled?

Is all spectral rendering handled as simulation? Are there technique more tailored to 'consumer' rendering, such as for real-time or even just 'realistic looking without solving full physical ...
8 votes
3 answers
651 views

### Ambient Lighting

On the Wikipedia page for the Phong model, it says that the ambient term is a constant, and just gets added on to the other terms. But on other pages like LearnOpenGL it says you should take the ...
• 577
7 votes
2 answers
149 views

### How do shaped lights work?

I know how to program directional lights, point lights and spot lights. Sometimes though, people have lights that are shaped - like bars, or even a torus. How does that work from either a ray based ...
• 7,351
7 votes
1 answer
1k 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 ...
• 173
7 votes
2 answers
3k views

### Physically Based Area Lights

So after reading https://www.guerrilla-games.com/read/killzone-shadow-fall-creating-art-tools-for-a-new-generation (a guerilla games presentation on PBR) I noticed the Area lights as opposed to the ...
• 2,423
7 votes
1 answer
4k views

### Does PBR incur a performance penalty by design?

I am wondering if the various PBR models used in modern game engines for real time are heavier in terms of computation, that more classic approaches to rendering. Worded differently, is PBR just a ...
7 votes
1 answer
1k views

### Confused about prefiltering environment maps (Manson 16)

I'm working my way through this paper about GGX-filtering environment maps: http://www.ppsloan.org/publications/ggx_filtering.pdf I find myself stuck on the basics. In particular, I am confused by ...
7 votes
2 answers
3k views

### Better Shadow Mapping Techniques

Currently I have basic shadow mapping setup in my engine. I am currently trying to implement something more realistic like PCSS (percentage closer soft shadows), to get a more physically accurate ...
• 2,423
7 votes
1 answer
1k views

### Path Tracing With Multiple Lights

I've got my path tracer working great for a single light, but I'm having trouble coming up with a solution for scenes with multiple lights. My first thought was to just send a ray to each light and ...
• 389
7 votes
1 answer
594 views

### Legendre Polynomial equation in Spherical Harmonics

I recently started to read about spherical harmonics. I have a question about this spherical harmonics basis function equation which is mentioned in this StupidSH article: What are those lm() and Re()...
• 233
7 votes
1 answer
2k views

### Constant screen-space-width rim shading

As of lately I've been studying a bit of shaders (in Unity), and am trying to recreate the "light-based inline" that can be observed in the latest Legend of Zelda. But maybe the task is a bit above my ...
• 171
7 votes
1 answer
3k views

### What is Radiosity?

After reading a wikipedia article about Global Illumination It mentions a variety of techniques like Ray Tracing, Path Tracing and Ambient Occlusion. One technique it mentions is Radiosity which I don'...
• 2,423
7 votes
2 answers
1k views

### Multiple Lights Shading - One Pass vs Multiple Passes

I was looking into ways to implement multiple lights shading and I've noticed Unity uses multiple passes to achieve it. It performs a base pass to apply the brightest directional pixel light + 4 ...
• 1,156
6 votes
2 answers
408 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-...
• 7,351
6 votes
1 answer
137 views

### Amount of light reaching the sensor of pinhole camera model

Consider hypothetical camera with pinhole (in mathematical sense) lens and is sensor, like in below image. Is it the case that the central region of the sensor will receive more light (pixels will be ...
• 203
6 votes
1 answer
603 views

### What is the basis of rendering light caustics?

I am not looking for textbooks and related how-tos, though I'm sure they can color the answer. I'd like to understand how we handle the rendering of caustic effects — and particularly time-saving ...
6 votes
2 answers
3k views

### How to calculate attenuation and radiance in PBR? (point and directional lights)

I would like implement physically based rendering, following this tutorial I was able to find a list of light sources ordered by lumens, but I have no idea how to use it in the calculations. ...
• 248
6 votes
1 answer
588 views

### How Sunlight is added in Bidirectional Path tracing?

How is distant directional light source(like sun) added in BDPT? If this is an indoor scene that gets sunlight through windows, how is this handled in BDPT(other than to consider Sun as a big disc far ...
• 698
6 votes
0 answers
136 views

### Injecting Virtual point lights into 3D Grid

I am currently trying to implement light propagation volumes in DirectX 11 and I have already done the RSM part which contains position, normal, depth and flux map generation. But for Injecting ...
• 233
5 votes
3 answers
2k views

### Formula for the ambient light intensity of a scene?

I understand that ambient light is light that occurs a result of light from a given source refecting off an infinite number of points in a scene, thereby illuminating all objects in the scene ...
5 votes
2 answers
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: ...
• 2,423
5 votes
1 answer
440 views

### Why is spherical harmonics used in low frequency graphics data instead of a spherical Fourier transform?

I'm curious why spherical harmonics are commonly used in real time graphics instead of a spherical Fourier transform. I get that spherical harmonics are in a sort of frequency space (like FT is) so ...
• 7,351
5 votes
1 answer
2k views

### Modern way of light sources in OpenGL?

In older versions of OpenGL there were things like: glLight(...) gl_LightSourceParameters The modern way of doing lighting is passing light source parameters manually to the shader in vao-s? Or ...
• 303
5 votes
2 answers
224 views

### What is missing in this image that stops it from looking like a photograph?

Look at this image: This is CG, Saya, a project meant to make as real CG as possible to the point of becoming indistinguishable from reality. I would say that it is pretty believable. But, it still ...
• 51
5 votes
1 answer
2k views

### Bloom in DirectX

How can I make an object give the effect that it is giving out light when it isn't? I basically want to make an object glow, for example Neon Lights. Also Area Lights in my engine work properly but to ...
• 2,423
5 votes
1 answer
2k views

### Alternatives to Ambient Occlusion

Recently I wanted to improve the lighting in my game engine, naturally I looked towards Ambient Occlusion. I was considering SSAO but are there any better techniques? Maybe some that are Physically ...
• 2,423
5 votes
2 answers
2k views

### What is the difference between shading and shadowing?

Shading and shadowing are often mentioned in how to create realistic 3D graphics, but the distinction is not clear. Are both responsible for the generation of shadows, or do they refer to the same ...
• 181
5 votes
1 answer
268 views

### Unlit objects in deferred rendering

What is the best way to draw unlit objects with deferred? Like skybox, particles or just glowing objects? I thought about mask in alpha channel, check it in light pass and just set diffuse color but ...
• 556
5 votes
2 answers
266 views

### Special directional light type

I am currently trying to implement a specific directional light type. This light type has been used in the game INSIDE and is called orthogonal spotlight (aka local directional light). I assume that ...
• 1,169
5 votes
2 answers
267 views

### Radiance at a nearly perpendicular angle is almost infinite?

As far as I understand, radiance is a measure of the "intensity" of light in a direction defined as a differential cone . It's measure is Flux per solid angle per projected area. \$L = \frac{d\Phi}{d\...
5 votes
1 answer
112 views

### Where are the highlight definitions inside of my shader?

I have a pretty good glow shader going now thanks to some tips from people here. However there are a few things that bother me that could maybe be better. #1 Definition of the particles A lot of ...
• 1,365
5 votes
1 answer
961 views

### How to compensate low amount of rays reaching the light in a Path Tracer

I am trying to implement for research purposes a path tracer, but so far but results are not so good and I will explain you why. The general idea before getting to the code: I am working on paths ...
• 325
5 votes
1 answer
202 views

### Error with tube lighting

I have recently been working on area lights for a small open source game engine called Urho3D but have run into an issues when rendering tube lights where the lights look the same as sphere lights ...
5 votes
0 answers
182 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 ...
• 2,195
5 votes
0 answers
248 views

### Dual paraboloid shadow texture edge seams

I implemented dual paraboloid shadows for point lights. The goal was to reduce the number of shadow passes. Also the target is GLES3.0 so no layered rendering is available. The shadows work, and ...
• 239
5 votes
0 answers
1k views

### Percentage-closer Soft Shadows implementation

I am trying to implement the Percentage-closer Soft Shadows (PCSS) from NVidia inside Unity but I am facing some issue and I don't know where they come from and then, I do not know how to solve them......
• 1,169
4 votes
2 answers
727 views

### Path tracer not rendering shadows

I am trying to implement for research purposes a gradient-domain path tracer. In order to achieve this step I first need a working Path tracer. I have been creating one so far but results are wrong ...
• 325