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12 votes
Accepted

What explains the high specularity of metals?

Warning: I am not a physicist. As Dan Hulme already explained, light can't travel through metals, so dealing with IOR is a lot more... complex. I will answer why that happens and how to calculate the ...
Samu's user avatar
  • 546
9 votes

Why does the 1/r² term appear with point sources?

The concept of a point source is an approximation. Physically, light sources are extended objects and emit light from every point on their surface; but when you're far enough away (i.e. the distance ...
Nathan Reed's user avatar
7 votes
Accepted

What physical properties are “lacking” to keep this 3D scene from looking like a real photograph?

Few things, but usually this is what it takes to make the difference: 1- the material reflection at his head, he is bald, yet the diffuse texture shows color difference where the hair is, this means ...
Georges D's user avatar
  • 186
6 votes

What explains the high specularity of metals?

Look at the refractive index of several metals. They are all complex numbers and the math does work out when you put this into the fresnel equation: you get the expected high reflectivity at all ...
Olivier's user avatar
  • 1,585
5 votes

Why does the 1/r² term appear with point sources?

It is the inverse square law of light for a pure point light. $E = \frac{I}{r^2}$ Where E is illuminance and I is pointance or power/flux per unit solid angle.
Syntac_'s user avatar
  • 561
5 votes

Resulting Probabilty Density in Path Tracer for paths using Next Event Estimation

I don't have any experience with Gradient Domain Path Tracing, but here are my thoughts: There seems to be a different problem If you look carefully at the little spikes of distortion in the final ...
trichoplax is on Codidact now's user avatar
5 votes
Accepted

Can we use PhysX in WebGL?

PhysX is a C++ API and can thus not directly be integrated with the JavaScript-based WebGL. Depending on your needs, you have the following options: Use a JavaScript-based physics engine, mostly ...
David Kuri's user avatar
  • 2,293
4 votes
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Total emitted power of diffuse area light

Radiance (in terms of flux) has the following definition: $L_o = \frac{\mathrm{d}\Phi}{\mathrm{d}\omega^\perp\mathrm{d}A} = \frac{\mathrm{d}\Phi}{\cos{\theta} \mathrm{d}\omega \mathrm{d}A}$. Thus in ...
Vanbus's user avatar
  • 304
4 votes
Accepted

How would I create a virtual cabling system?

The shape you’re trying to draw is called a catenary: it’s the shape that a cable/cord of constant density takes when supported at each end. You’ll have to do some research to find a parametric ...
Noah Witherspoon's user avatar
4 votes

What physical properties are “lacking” to keep this 3D scene from looking like a real photograph?

I think you identified the problem yourself in your question : it still definitely looks like a 3d model It's obviously hard to tell and subjective, but while many things are off in this picture, ...
Vingt-2's user avatar
  • 53
4 votes

What physical properties are “lacking” to keep this 3D scene from looking like a real photograph?

Hard to say because we can not see the code. Subsurface scattering might be part of that equation. I would just point out that human brains are extremely specialized in facial recognition. It has ...
joojaa's user avatar
  • 8,417
4 votes

What is the effect of the BRDF denominator?

Firstly, I highly suggest reading Eric Heitz's paper "Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs", which covers the full derivation of microfacet-based BRDFs. The $\frac{...
RichieSams's user avatar
  • 3,732
4 votes

Why does the 1/r² term appear with point sources?

I'll give an intuitive idea of the reason in this answer. Once this intuitive idea is grasped, it can be easier to absorb the mathematical descriptions. Other people find it easier the other way ...
trichoplax is on Codidact now's user avatar
3 votes
Accepted

Why is the approximation valid, in the formula provided by Brian Karis?

"the information that $f(l_k,v)$ carries is low-frequency enough": As IneQuation explains, low-frequency was used to refer to the detail of the brdf function. I did actually mean that $f_r$ was low ...
Sebastián Mestre's user avatar
3 votes

Understanding lighting for physically based rendering

Referring to the answer that lightxbulb already gave, you can find a very in-depth explanation of the physics of light and their simulation in the thesis of Eric Veach named "Robust Monte Carlo ...
Erik Wessel's user avatar
3 votes

Understanding lighting for physically based rendering

Here you have a full repository with a lot of papers about light transport. There's also a folder named 'theory' where you can get both intro and advanced refs regard light physics. And much more. I'm ...
Max Tarpini's user avatar
3 votes
Accepted

What's the difference between irradiance and fluence/radiant exposure?

I can only cite what I have learned in my lecture on Global Illumination techniques which was unfortunately some time ago: Radiant Power : The amount of energy emitted by a light source in unit time. ...
Dragonseel's user avatar
  • 1,810
3 votes

Creating Sparks using Code

For the lightning, I recommend using a midpoint displacement algorithm. You start with a line segment between any 2 points A and B (this works in either 2D or 3D). Calculate the midpoint of the ...
user1118321's user avatar
  • 3,401
3 votes

2D metaballs with marching squares and linear interpolation

as promised, here my answer to your question. As I can't follow your code completely (I spend most of my time implementing my code :D ) I can only explain to you what the last step is. So why do we ...
realvictorprm's user avatar
3 votes

Rendering Hypercentric Perspective

You can approximate the view of a hypercentric camera with an ordinary 3D perspective camera if you are able to manipulate the projection matrix, and/or reverse the direction of the depth test. In a ...
Nathan Reed's user avatar
2 votes

What explains the high specularity of metals?

The refractive index is related to the speed at which light travels through the medium, and only applies to materials which are at least partially transparent. Metals are electrically conductive, so ...
Dan Hulme's user avatar
  • 6,770
2 votes

Total emitted power of diffuse area light

I think the assumption (perhaps stated perhaps not, I dont' have the text handy) is that the radiance is emitted in a cosine-lobe distribution. This means that there's falloff in proportion to the ...
GroverManheim's user avatar
2 votes

What physical properties are “lacking” to keep this 3D scene from looking like a real photograph?

I see several things that are off in addition to what others have said. He doesn't appear to be breathing. He's in a very cold place (it appears to be snowing), yet there's no breath in front of his ...
user1118321's user avatar
  • 3,401
2 votes

Why does the 1/r² term appear with point sources?

Thanks for your answers. That was helpfull. This is how I understand the 1/r² term for point source (tell me if I'm wrong). Let's take the BRDF definition : $$ L_o = \int f(\omega, \omega_o) \, dE$$ ...
Livetrack's user avatar
  • 169
2 votes

Why does the 1/r² term appear with point sources?

Say the point light is at $P_L$, the shading is happening at $P_S$ It's true that the radiance is constant along a shadow ray $P_L \rightarrow P_S$, but that's not the key property for solving the ...
Karl Schmidt's user avatar
2 votes

Blackbody curve to floating RGB

The Open Shading Language has a complete implementation which is based on this source code from Color Rendering of Spectra by John Walker, according to the comments. I can't vouch for its theoretical ...
Olivier's user avatar
  • 1,585
2 votes
Accepted

Rendering Hypercentric Perspective

The answer is yes. You need 2 things: View space coordinates of the object Projection function for the hypercentric perspective camera. The second one can be found in here. The overview of the model ...
Kaan E.'s user avatar
  • 461
1 vote
Accepted

Physically Based Shading for Diffuse surfaces

So after reading up some more research papers and the concepts of most people working in this field here and there, I've reached an answer I'm satisfied with. If someone disagrees or thinks there is a ...
gallickgunner's user avatar
1 vote

Rendering Equation for photons carrying flux

It'd be hell a lot easier if this were on graphicsexchange, since I can't use latex here but anyways. In the first pass of Photon Mapping you don't need to use the Flux form of rendering equation. ...
gallickgunner's user avatar
1 vote
Accepted

How to rotate a shape in another 3D software so that the rotation matches with the rotation in Blender?

I just had to make the following changes to [manually] change the coordinate system of FleX to the one that Blender uses: ...
Amir's user avatar
  • 241

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