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Questions tagged [lighting]

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0answers
6 views

Non ray-traced Crepuscular rays/Under water godrays what *angle realistic* methods can I use?

I'm trying to figure out how to render under water godrays, I've found numerous methods that use things like rendering fake caustics via ray marching through the medium, collecting values based upon ...
3
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3answers
742 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 ...
1
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1answer
71 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
32 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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0answers
33 views

What vectors are used to assign light intensities?

What vectors are used to assign light intensities to surface points during the rasterization process in the Phong Lighting Model? A diagram would really help to see how this works.
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1answer
46 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?
11
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4answers
488 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, ...
6
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2answers
166 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-...
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0answers
94 views

Spherical harmonics ringing after coefficient scaling

I have a light probe system which gathers lighting information in a form of spherical harmonics. What I do is project surrounding static geometry surface colors (without lighting) onto SH. Then, in ...
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0answers
87 views

Image-Based Lighting and Light Probe usage understanding

I have read this thread about Light Probe but still confused. Why does IBL (Image-Based Lighting) is used only for local illumination compare with light probe ? From what I read, light probe is for ...
3
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1answer
136 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
151 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 ...
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0answers
30 views

How calculation-intensive is a complex light source?

Say you have a translucent material with a pattern. You place it on top of another surface, and then move it away. The light on the second surface should go from a copy of the pattern to being ...
1
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1answer
44 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 ...
2
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0answers
98 views

Not understanding the lighting equation for volumetric cloud rendering

I've been looking The Real-time Volumetric Cloudscapes of Horizon-Zero Dawn, but I'm very confused by a few terms. The presentation mentions "The Henyey-Greenstein phase function" on page 54, ...
2
votes
1answer
199 views

Radiosity normal map light baking

I'm trying to implement radiosity normal maps from the old Valve paper: Half-Life® 2 / Valve Source™ Shading.pdf | valvesoftware.com I've tried generating the light maps using Vray and 3dStudio max, ...
1
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1answer
85 views

Light Falloff through a grid

I'm playing with a grid-based lighting system, where light is transported and accumulated through a grid. I initially tried attenuation based on ...
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0answers
58 views

Omnidirectional Faded Soft Shadows

I'm doing research to implement a shadow algorithm for omnidirectional soft shadows in a real-time 3D renderer. I've read about PCF but to me it doesn't look very realistic since it doesn't "fade" ...
1
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1answer
181 views

How to interpolate vertex normals for Phong lighting when barycentric coordinates are negative?

I'm interpolating normals for Phong lighting models. Since I am calculating in the light of each pixel, I'm doing the interpolating after the viewport transform has been applied. So I save a version ...
4
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1answer
178 views

Experimental real-time shadowing techniques?

The three most popular shadowing techniques for real time applications are: Shadow maps Advantages: Fast "Simple" Disadvantages: Numerical limitations lead to artifacts and jaggy shadows You ...
3
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1answer
128 views

How does opengl fixed function pipeline determine specular lighting with an orthographic projection

I have a scene set up with an orthographic projection with the near / far set from -5000 to 5000. The model view is centered at 0 in the z-axis. I am rendering a sphere centered at z=0 with lighting,...
1
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1answer
78 views

Ringlike artifacts produced by rays bouncing off a light source

I recently set up a (very basic) ray-marched path-tracer, and I'm getting strange surface patterns on my area light [link]. I'm using known-valid analytical normals for the light's surface, and the ...
3
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1answer
253 views

Directional Light ViewSpace Calculation

I am a bit confused in terms of directional light calculation in OpenGL. Generally we care about the direction of the directional light and we use it with the normal and view (toCamera) vector to ...
1
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1answer
44 views

What program can bake transparent light maps?

So I have this racing game I'm trying to modify that uses lightmaps that fade to transparency for light sources. An example from the game: I've been trying to produce a similar effect but with no ...
5
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1answer
134 views

Roughness Remapping

I have been recently exploring physically-based rendering (PBR), but there is one part that still confuses me. I don't quite get roughness remapping, as described in the PBR section on Learn OpenGL. ...
1
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0answers
67 views

Culling point lights with specular

Well, it's easy to cull point lights when you only need to know the diffuse bounds, but what to do when materials around the light have a specular reflections enabled? The method won't work in this ...
2
votes
1answer
956 views

Path tracing with Next event estimation and area lights auto occlusion

I am working my way through my first path tracer and I am currently designing how to deal with area lights. I have two questions: Each object in my scene can have a Light attached to it, this is how ...
1
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1answer
169 views

How do you implement perspective correct Gouraud shading across a triangle?

What's the algorithm for doing so? I have flat shading working and I have perspective correct texture mapping working. Is the way your raster Gouraud shading much different from the perspective ...
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0answers
43 views

Lighting ramps compressed to zonal harmonics

Let's say I have a lighting lobe represented as a ndotl ramp texture, how do I compress it into a zonal harmonic?
4
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2answers
255 views

How does UnrealEngine handle depth?

Today I found something really interesting (I've never seen something like that). While debugging the buffers used in lightning, I see that the depth information is stored in what looks like cascades ...
5
votes
2answers
1k 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. ...
1
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0answers
42 views

Emission maps that interact with a bump map

I am trying to create an effect where a bumpy billboarded texture is illuminated by a emission map that is also billboarded but is logically closer to the camera in 3D space. In this way a blue ...
7
votes
1answer
593 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 ...
6
votes
2answers
319 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 ...
3
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0answers
129 views

Exact Formula for Diffuse Hemisphere Lighting

The OpenGL Programming Guide states the formula for diffuse hemisphere lighting on a surface with normal vector $\vec{n}$ as $L_o(\vec{n}) = L_i(\uparrow) (1-\frac{1}{2}\sin(\theta)) + L_i(\downarrow)...
5
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2answers
203 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 ...
1
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2answers
453 views

How to find Light Direction from a Point on a surface to an Area Light

How can I a find the Light Direction/Ray from a Point on a surface to an Area Light? Is there a universal technique to do this for all types of lights (circle, rectangle, sphere & tube)? Although ...
3
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1answer
264 views

Does smooth lighting work with Gouraud shading on single triangles?

I'm currently working on a project where a 3D model gets computed through an isosurface algorithm. This algorithm outputs single triangles with vertices and normals, but without indices. So therefore ...
6
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0answers
148 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 ...
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0answers
40 views

What could cause realtime lighting within a viewport to be calculated on the wrong part of the screen?

(I initially posted this in a section that is less suited for the particular issue, oops) I'm having this issue on some of my client's computers (this is for a Unity asset) that I cannot reproduce on ...
6
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3answers
491 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 ...
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0answers
48 views

Specular Highlight Gray When Behind Model

What would cause this grayscaled backside? When my camera is behind my model I see a grayscale specular highlight. However, in front of it is perfectly fine. Here's my shading code. (Software ...
7
votes
1answer
369 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 ...
-1
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2answers
806 views

Emission of light from texture on WebGL

I have to build a texture of a cube that models the emission of light by the object. Any tips? I really don't know where to start.
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0answers
320 views

WebGL Spotlight

I have to add a spotlight to my rotating cube so this is my code: HTML ...
5
votes
1answer
247 views

Irradiance Map Equation What is “dω”?

Link to paper : Irradiance and Incoming Radiance | lawrence.edu Using a shader to compute En Computing En as described above is a very compute intensive operation, because we have to compute ...
1
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1answer
170 views

How to organize Lights and Models?

I'm interested in how to organize in code (I prefer C++) lighting. Problem is: I have Scene which contains Model where model ...
6
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1answer
111 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 ...
4
votes
1answer
246 views

Phong: Real-time rendering of Metal and Plastic Materials

Using a shader that works like Phong, what would be the difference between painted Metal and plastic? I seem to remember reading in books years ago, that I no longer have access to, the following: ...
3
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3answers
191 views

What's the concept of “Ray” really?

I'm learning Ray Tracing using this MIT tutorial. I've heard Ray Tracing only in the context of lighting. I.e. I understand that ray casting is used to light an object that has been already drawn. ...