Path tracing 101

Starting easy.
tuomlarsen
Posts: 16
Joined: Mon Oct 29, 2012 6:02 am

Path tracing 101

Postby tuomlarsen » Thu Nov 01, 2012 9:23 am

Hello!

I'm totally new to all this, please bear with me: I implemented my first path tracer, it only uses spheres and needs to shoot *a lot* of rays to see something at all when the light source is small. Now I would like to add some features which are considered "essential" but I have many questions about them:

(I'm interested in simple features, i.e. I know I can get better rendering from MLT and what not but such thing are currently totally over my head, so, I'm going through this step by step....)

- Camera. What is a "pin hole camera"? Why can't I just shoot rays into scene from screen pixels in the camera direction?

- Tone mapping. Do I need it? If I were to use "linear" tone mapping isn't it the same as using weaker light source? If I understand it correctly, it is kind of auto-exposure technique - doesn't it create problem, say, when I want to render under-exposed picture?

- Acceleration structure. I would like to add triangle primitive so I guess this is by far the most "essential" feature. I saw many articles on which one to choose and the all differ in conclusions :). So, if my scenes are static and I want to keep things simple, which one should I try? BVH, KD-Tree, Octree, something else?

- Light. I saw at http://kevinbeason.com/smallpt/#mods that adding "explicit light sampling" speed-up the rendering considerably. As the source code for it is a bit unreadable for me - what is it? Are there any tutorials or articles about it? I guess this is the other "essential" feature next to the acceleration structure, right? How does it work - when a light bounces off a surfaces I just randomly choose whether I go somewhere else or towards a light?

- Materials. And this is something I totally don't understand. All a material does is to affect how a way bounces off its surface? I read about "hemisphere" sampling and "cosine" sampling but so far I'm lost on this one...what are they? Does it somehow relate to previous paragraph about light searching?

- I also read about using "pseudo-random" numbers, as opposed to using "random" ones, as it reduces noise (?). But where do I use them? In pixel antialiasing? For location of sub-pixels for ray shooting from camera? Or for choosing the next direction for this "bouncing off" material?

- Else. What else do you consider as "essential"?

Thank you very, very much in advance!

ingenious
Posts: 273
Joined: Mon Nov 28, 2011 11:11 pm
Location: London, UK
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Re: Path tracing 101

Postby ingenious » Thu Nov 01, 2012 11:13 am

It will be better both for you and the other forum members if you just get a book that explains all these things. Your post above sounds to me a bit like: "Hey, chemists, I'm new to chemistry, I mixed vodka and wine successfully last night, and now I want to know all the basics in chemistry to be able to make some great cocktails! Tell me everything you consider essential in chemistry" :mrgreen:

So, get a book like "Physically Based Rendering: From Theory to Implementation", eat it up, and then people will be happy to help you with questions that are not answered in the book.
Image Click here. You'll thank me later.

tuomlarsen
Posts: 16
Joined: Mon Oct 29, 2012 6:02 am

Re: Path tracing 101

Postby tuomlarsen » Thu Nov 01, 2012 11:35 am

I understand that these questions wont make up for reading a book. I was just hoping for a few one-line answers as an introduction into more advanced rendering.

Dade
Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

Re: Path tracing 101

Postby Dade » Fri Nov 02, 2012 11:04 am

ingenious wrote:So, get a book like "Physically Based Rendering: From Theory to Implementation", eat it up, and then people will be happy to help you with questions that are not answered in the book.


http://www.pbrt.org/


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