# Questions tagged [physically-based]

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### Why is the indirect illumination (using IBL) in my PBR shader overpowering everything?

I'm trying to implement a basic form of physically based rendering (PBR) and I am using the PBR tutorial from learnopengl dot com as a reference. The PBR I am implementing consists of two parts, ...
589 views

### How to determine RGB values given a display spectral response curve?

I am reading Physically Based Rendering section 2.2.2 on RGB color. I am trying to understand how, given a display spectral response curves for rgb intensities, we can choose the intensities so that ...
68 views

### Point light source radiance

I was reading Deriving radiance from irradiance and intensity and the last comment said that by dividing $r^2$ we convert radiant intensity to irradiance. What confuses me then is the fact that for ...
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### Diffuse irradiance map : confusion about photometric vs radiometric units

I have spent the longest amount of time just taking the terminology for granted & have only just recently started studying or at least trying to understand the difference between radiometric and ...
1 vote
58 views

### How is the beam transmittance calculated in PBRT V3?

In pbrt v3, the book gives this description of beam transmittance, but I don't know how to solve the differential equation like it says to get Tr , can someone please tell me how to solve the ...
75 views

### What's The Math Behind This Cloth Animation?

I progammed a simple cloth animation. Initially I tried to implement Hooke's law, but it wasn't numerically stable, presumably because I used explicit Euler. Anyway, I came up with something (WebGL2 ...
264 views

### Rendering Hypercentric Perspective

I came across some Non-Euclidean Games which involve Hyperbolic Spaces, Spherical Spaces, Portals, etc. And, I noticed that they give quite deep feel of what Non-Euclidean Spaces feel like. So, I was ...
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 ...
90 views

### PBR pipeline with multiple HDR images?

I believe I already know the answer to this question, but I want to make sure I'm understanding this correctly. Within a physically based rendering pipeline, you calculate your indirect lighting from ...
167 views

### State of the art in real-time global illumination algorithms [closed]

What is the state of the art in global illumination algorithms in real time applications? Which algorithms or categories of algorithms are actually used in the wild and what are their characteristics (...
1 vote
446 views

### How to change a RGB value using a radiance value?

I am new to this awesome community, I am currently writing a ray tracer but I hit a problem... Let's say I have a surface(material doesn't matter) of colour [1, 0, 0] in RGB, and the radiance reaching ...
164 views

### Ray casting and rasterization 101

Recently I've became an intern in company-name and my internship task is(for now) create rasterization using rays. I'm mostly interested in pure math, so basic ...
4k 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 ...
1 vote
128 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 ...
889 views

### Why is eye-based ray tracing preferred over light-based ray tracing?

It seems that virtually all path tracers use eye-based or view-based path tracing. That is, the light rays originate from the camera rather than the light source. The reason given for this everywhere ...
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 ...
859 views

### How correct is rendering in XYZ / linear RGB space?

I have a spectral power distribution (SPD, 5 nm steps) for all light sources in the scene and SPDs for the reflectance of all surfaces under any light / viewer angle in question. I'm going to ...
1 vote
220 views

### Understanding lighting for physically based rendering

i wanted to ask if you know the best books or resources to understand light physics. I have heard that Subrahmanyan Chandrasekhar's book "Radiance Transfer" is very good. Any other books or ...
5k views

### What are the current open problems in Computer Graphics?

I did a quick investigation about the topic but there doesn't seem a decent resource to find related problems without digging into latest CG papers (unlike CS problems you can easily find a Wikipedia ...
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### How is the image reconstruction filter on the path space defined in terms of the filter on the raster space?

Say we have a image reconstruction filter $h:R\to\mathbb R$ defined on the raster space $[0,w]\times[0,h]$, where $w,h\in\mathbb N$ define the width and height of the image plane in pixels, ...
94 views

### Relation between camera sensor responsivity and image reconstruction filter associated with a pixel

Let $W_{\text e}$ denote the camera sensor responsivity (i.e. importance) and $h_j$ and $W_{\text e}^{(j)}$ denote the image reconstruction filter and sensor response associated with the $j$th pixel, ...
64 views

### Is casting a shadow ray non-symmetric in pbrt?

According to the description in the book, Scene::IntersectP() "checks for the existence of intersections along the [passed] ray". This operatorion should be ...
54 views

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### Ocean Wave Rendering

How could I generate the waves for a water body with whitecaps & foam and variable intensity of the waves? Is the surface a mesh with a normal map? Is there a formula for generating that? Is there ...
957 views

### PBR - How to handle multiple BSDFs and material type

So I am in the midst of writing my own path traced renderer and right now I have only implemented the old Blinn-Phong models where we separately calculated the diffuse and specular components of the ...
361 views

### How is Iridescence handled in a Path Tracer?

I have little knowledge of this topic but from what I gather in a Ray Tracer each ray is given its own wavelength as opposed to an RGB value. This automatically simulates Dispersion and Fluorescence. ...
1 vote