Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [pathtracing]

For questions about the path tracing Monte Carlo algorithm for physically accurate global illumination, or its variants.

24
votes
2answers
3k views

Path tracing the Cook-Torrance BRDF

-- Sorry for the long post, but I prefer to do that way because "Devil is in the details." :) I am writing a path tracer from the scratch and it is working nicely for perfectly diffuse (Lambertian) ...
12
votes
1answer
3k views

Progressive Path Tracing with Explicit Light Sampling

I understood the logic behind the importance sampling for the BRDF part. However, when it comes to sampling light sources explicitly, all becomes confusing. For example, if I have one point light ...
13
votes
1answer
2k views

Choosing Reflection or Refraction in Path Tracing

I am trying to implement refraction and transmission in my path tracer and I'm a bit unsure on how to implement it. First, some background: When light hits a surface, a portion of it will reflect, ...
17
votes
3answers
4k views

Is Russian Roulette really the answer?

I have seen that in some implementations of Path Tracing, an approach called Russian Roulette is used to cull some of the paths and share their contribution among the other paths. I understand that ...
21
votes
1answer
2k views

Anti-aliasing / Filtering in Ray Tracing

In ray tracing / path tracing, one of the simplest way to anti-alias the image is to supersample the pixel values and average the results. IE. instead of shooting every sample through the center of ...
7
votes
2answers
603 views

Path Tracing & Materials

I'm wondering about the technique used when sampling a layered material for the next event in a path tracer. I have a material with three layers: a base diffuse, specular and sheen lobes. How does one ...
11
votes
1answer
585 views

Path tracer - multi layered materials and importance sampling

I'm currently trying to implement a Monte Carlo path tracer. I've done some research and it seems that a common approach to materials is to use a layered model. Something like this: When light hits ...
10
votes
1answer
912 views

Full Monte-Carlo Volumetric Scattering

I would like to add full monte-carlo volumetric scattering to my path tracer, but I'm having a hard time researching how to do it. Let me explain what I would like to do: A ray enters a material, and ...
8
votes
0answers
589 views

More accurate Fresnel approximation for a RGB-based Path Tracer

I'm writing a path tracer and, for the moment, spectra related data (spectral power distributions and spectral reflectance curves) are stored as RGB tuples. In the Cook-Torrance specular BRDF I am ...
7
votes
2answers
891 views

Is it expected that a naive path tracer takes many, many samples to converge?

I have a naive diffuse/emissive material path tracer implementation (pinhole camera) and am seeing it take a very large number of samples per pixel to converge - like probably in the millions - and ...
7
votes
1answer
700 views

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

I am trying to implement my own Gradient Domain Path Tracer by following the code of this guy who already implemented it: https://gist.github.com/BachiLi/4f5c6e5a4fef5773dab1 I already managed to ...
3
votes
1answer
245 views

Should direct illumination and path tracers render the same scene equally bright?

I am using the book Ray Tracing from the Ground Up by Kevin Suffern to build my first ray tracers in Java. Based on the theory, I expected that direct illumination and simple path tracers render the ...
5
votes
1answer
729 views

Volume Rendering (Path Tracing & Real-Time)

I have a few doubts and questions regarding volume rendering, I was hoping someone here could help me understand. I commonly hear the terms 'Ray-Marching' & 'Volume Rendering' being used together ...
4
votes
1answer
445 views

Efficiently sampling specific surfaces using MIS in path tracing

Apologies for posting two questions in one post, but as they are relevant I kept them in one. Question 1 In the definition of multi sample estimator that Veach has defined, the integrand is the same ...
2
votes
1answer
95 views

Naive Path tracer produces much darker images than Explicit light sampling

So I just thought of comparing the results from a Naive Path tracer and one using Next Event Estimation aka Explicit Direct Light Sampling. However the results from the Naive PT are very dark. Is ...
1
vote
1answer
118 views

Path tracer isn't converging

So I just completed a naive path tracer that uses explicit direct light sampling. Problem is the path tracer isn't converging. It's like a raytracer, showing a single image on each pass. More info on ...
6
votes
1answer
176 views

Mix shader looks wrong on my path tracer

I apologize if my methods seem way off because this is my first time trying to build a path tracer and I'm struggling quite a bit. Currently, I am trying to mimic the "mix shader" node in Blender 3D ...
3
votes
1answer
199 views

Multiple Importance Sampling in Path tracer produces Dark Images

So I recently implemented Multiple Importance Sampling in my path tracer which was based on next event estimation. The problem is without MIS I get images like, This is obtained by setting ...
2
votes
0answers
38 views

How to implement explicit light sampling when implementing path tracing?

I implemented a path tracer and got a similar result like this one. Sample: 4096, time used: 537.05s The algorithm is exactly the same as the one in wikipedia, where only the Gathering Path is ...