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# Questions tagged [theory]

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15 votes
2 answers
710 views

### Problem with definition of BSDF and radiance

When I was reading theory behind physical based rendering I noticed that definition of BSDF and radiance has some problems. For example BSDF of purely specular surfaces is zero almost everywhere and ...
1 vote
0 answers
56 views

### Term confusion about volume scattering

We have two different terms, for example, let's talk about scattering only. Scattering coefficient Scattering cross-section These two terms are supposed to have different physical meaning. I read it ...
1 vote
0 answers
172 views

### Applying Monte-Carlo methods in path tracing

I've noticed that I consistently get worse results in path-tracing when I try to do monte-carlo correctly compared to when I don't, and I think this might be because of a fundamental misunderstanding. ...
0 votes
3 answers
262 views

### FLOP - exact definition

I am interested in how much a GPU can actually calculate. When learning about rendering, it seems like a good idea as well. My Question: WHAT EXACTLY is a Floating Point Operation? I know what a ...
0 votes
0 answers
110 views

### coverage vs transparency

2D application users seem to be using transparency as a proxy for coverage more often than not. However they are not the same, although nearly everybody makes the assumption that they are. Given that ...
2 votes
1 answer
1k views

### Difference betwen Rendering Equation, Lighting model, Ray Tracing, Global Illumination and Shadows?

What is the difference between all these techniques? I know what a lightning model does, eg Phong, Flat, Gouraud. As far as I know both Ray Tracing and Global Illumination are just lighting models ...
3 votes
1 answer
797 views

### Rendering Fluid Simulations?

I've read about Lagrangian and Eulerian fluid simulations and here's what I take from their methods: Lagrangian - Simulating fluid particles by calculating displacement for each particle Eulerian - ...
4 votes
1 answer
250 views

### Pixel density / color channel depth ratio for dithered gradients

Dithering increases percieved color depth by adding a "noise" to an image on transform from high color depth (e.g. 32-bit floating point) to lower color depth (e.g. 8-bit integer). A prerequisite is ...
18 votes
1 answer
737 views

### Why integrate over a hemisphere (and not a sphere) to solve the rendering equation?

In most text books that I have seen, this is how the rendering equation is written: $$L_0( \omega_0)= L_e(\omega_0)+\int_{\Omega}{f(\omega_i, \omega_0)L_i(\omega_i)\,\mathrm{d}\omega_i}$$ Where \$\...