Computer Graphics Stack Exchange
Computer Graphics Stack Exchange

Questions tagged [physically-based]

85 questions
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How physically-based is the diffuse and specular distinction?

The classical way of shading surfaces in real-time computer graphics is a combination of a (Lambertian) diffuse term and a specular term, most likely Phong or Blinn-Phong. Now with the trend going towards physically-based rendering and thus…
David Kuri
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Physically based shading - ambient/indirect lighting

I implemented a physically based path tracer after studying PBRT by M. Pharr and G. Humphreys. Now I'm trying to apply physically based rendering to real time graphics using OpenGL ES (in an iPhone application). I want to start using Oren-Nayar and…
Fabrizio Duroni
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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 presentations to blog posts. Recently Matt Pettineo…
Arjan Singh
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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 camera. I got the principle right, but I'm looking…
teh internets is made of catz
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14
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3 answers

Correct Specular Term of the Cook-Torrance / Torrance-Sparrow Model

For a while I have been doing some research on the topic of Physically Based Rendering. One reflection model that is mentioned over and over is the Cook-Torrance / Torrance-Sparrow model. It seems like in each mention or explanation of this model a…
Thordal
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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, which is physically uniform in intensity. Gamma…
Maxpm
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Polarising reflection and refraction for a wrap around water surface

I want to render realistic images of water in an orbiting space habitat. The image does not need to be generated in real time, although I wouldn't want it to take weeks either. I'm looking for an approach that can generate realistic images in hours…
trichoplax is on Codidact now
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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 calculate in floating point precision and not clamp any…
David Kuri
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11
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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 something similar to determine where and how the…
Arjan Singh
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11
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16bit half-float linear HDR images as (diffuse/albedo) textures?

So I been thinking about this for a while and tried to google for an answer but without any success. If all your textures are 8bit LDR images, like JPEGs, couldn't that potentially cause conflicts with exposure control/tone mapping when rendering.…
Kristoffer Helander
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Compensation for energy loss in single-scattering microfacet BSDF models

Single-scattering microfacet-based surface models like the original Torrance-Sparrow BRDF or derived models like the BSDF for rough dielectric surfaces by Walter et al. neglect inter-reflection of light between microfacets, which results in energy…
ivokabel
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10
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Modelling Young's double slit experiment

Young's double slit experiment is very simple to set up and simple to explain, but it is an example of both diffraction and interference, neither of which are modelled by conventional raytracing. It is straightforward to render an approximation of…
trichoplax is on Codidact now
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Total emitted power of diffuse area light

I am reading the book Physically Based Rendering (Pharr, Humphreys). In the chapter on lights, they talk about approximating the total emitted power of different kinds of lights. For example, a point light's total power is intensity * 4 * pi. Here…
Rasmus Rønn Nielsen
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Area Lights in Path Tracing

I have been following the scratchapixel ray tracing tutorials online which have been great at explaining the theory behind everything & how to implement it. However, I reached the point where I want to implement Area Lights but I am clueless on how…
Arjan Singh
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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 different way to organize one's rendering pipeline,…
teh internets is made of catz
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