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Questions tagged [raytracing]

Questions specific to raytracing (as opposed to scanline rendering), the 3D graphics technique of intersecting rays from the camera with objects in the scene.

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18 votes
1 answer
10k 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 ...
Mustafa Işık's user avatar
31 votes
2 answers
7k 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) ...
user avatar
43 votes
2 answers
49k views

What is Ray Marching? Is Sphere Tracing the same thing?

A lot of ShaderToy demos share the Ray Marching algorithm to render the scene, but they are often written with a very compact style and i can't find any straightforward examples or explanation. So ...
psicomante's user avatar
15 votes
4 answers
19k views

How is Anti Aliasing Implemented in Ray Tracing?

After reading a few articles online I can confidently say I am clueless on how Anti-Aliasing works when using Ray Tracing. All I understand is that A Single Pixel/Ray is split into 4 sub-pixels and 4 ...
Arjan Singh's user avatar
  • 2,511
9 votes
1 answer
3k views

Path weight for direct light sampling

I originally wrote a pathtracer that just bounces by the BRDF and each sample is added to a buffer that divides by the current number of frames. Now I'd like to do next event estimation at each ...
newtorendering's user avatar
6 votes
3 answers
7k views

Mirror Reflections: Ray Tracing or Rasterisation?

Are mirror-like reflections in computer graphics purely handled with ray-tracing/ray-casting techniques or are there some situations where they are achieved through rasterisation?
Will D's user avatar
  • 115
4 votes
1 answer
3k views

Deriving radiance from irradiance and intensity

I'm reading PBRT and am stuck in chapter 5.4 about radiometry. In particular: We define the irradiance as the average density flux arriving at a surface with units $\frac{W}{m^2}$. So for a point ...
lyinch's user avatar
  • 223
2 votes
0 answers
164 views

Scaling of the final image in Metropolis Light Transport

I don't understand why the PBR implementation of Metorpolis Light Transport scales the final image by b / mutationsPerPixel. The authors write: Each Metropolis ...
0xbadf00d's user avatar
  • 203
25 votes
1 answer
4k 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 ...
RichieSams's user avatar
  • 3,792
19 votes
2 answers
13k views

Cause of shadow acne

I know how shadow mapping works but I am not getting the cause of shadow acne! Can anyone tell me cause of shadow acne in a simple way and how is it related to depth map resolution?
videogamechef's user avatar
17 votes
2 answers
1k views

Subpixel Rendering for a Ray Tracer

In font rendering, it is common to use subpixel rendering. The basic idea here is to break the pixel into its RGB components and then compute a value for each separately. Since each component is ...
geometrian's user avatar
  • 1,990
15 votes
2 answers
2k views

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 ...
teh internets is made of catz's user avatar
15 votes
3 answers
2k views

Non Real Time Raytracing

I've played with real time raytracing (and raymarching etc) quite a bit, but haven't spent that much time on non real time raytracing - for higher quality images or for pre-rendering videos and the ...
Alan Wolfe's user avatar
  • 7,801
15 votes
1 answer
12k views

Radiosity VS Ray tracing

Radiosity is basically what allows this: In a tutorial of Cornell University about Radiosity it is mentioned that: A ray-traced version of the image shows only the light reaching the viewer by ...
Armfoot's user avatar
  • 615
13 votes
1 answer
7k views

Does cosine weighted hemisphere sampling still require NdotL when calculating contribution for indirect light?

When converting from uniform hemisphere sampling to cosine weighted hemisphere sampling I am confused by a statement in an article. My current indirect contribution is calculated as: ...
Steven's user avatar
  • 315
12 votes
1 answer
1k views

What is the difference between importance sampling and mutiple importance sampling?

I can't understand math equations. I'm a graphic designer. What is "importance sampling"? What is "multiple importance sampling"? Could you explain easily, using illustrations and no math equations? ...
kangsume's user avatar
  • 121
9 votes
1 answer
1k 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 ...
user avatar
8 votes
1 answer
896 views

How to implement a realtime 2D light renderer with fog/colored light on the GPU?

Since long ago I wanted to implement a 2D lightning algorithm based on an idea I saw on YouTube. The video is realtime, but it runs on the CPU and the resolution is pretty low. I'm curious if anyone ...
sydd's user avatar
  • 253
7 votes
1 answer
196 views

2D sampling with multidimensional transformations

I'm currently learning mathemetical concepts of distribution and the way to use them in a ray tracer with the book "Physically Based Rendering". Let's start by uniformly sampling an hemisphere: As ...
Qzaac's user avatar
  • 73
6 votes
1 answer
3k views

Ray Tracing Shadows: The Shadow Line Artifact

By using smooth shading (i.e. interpolation of normals), an object can have a smooth look despite low polygon count. A nasty artifact that can happen when casting shadow rays is the Shadow Line ...
David Kuri's user avatar
  • 2,293
6 votes
1 answer
354 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 ...
Henry Bergin's user avatar
5 votes
2 answers
2k views

Could we dispense the near clipping plane?

Would it be, at least theoretically, possible to render without a near clipping plane? Could raytracing ignore this perchance? Quite many budding 3d artists have a WTF moment the first time they ...
joojaa's user avatar
  • 8,447
4 votes
1 answer
1k 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 ...
Jeroen's user avatar
  • 125
4 votes
1 answer
1k 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 ...
ali's user avatar
  • 740
2 votes
1 answer
2k views

Probability density function while using spherical coordinates

I'm following this tutorial where at somepoint the derived PDF for spherical coordinates for a Lambertian surface is \begin{array}{l} p(\theta, \phi) = \dfrac{\sin \theta}{2 \pi}. \end{array} But as ...
Row Rebel's user avatar
1 vote
1 answer
354 views

Path tracing - cannot converge diffuse sampling + oversaturation

I'm in process of creating progressive path tracer using DX12 + DXR. I managed to create working raytracing code + pathtracing code with multiple bounces but I'm experiencing problems stated below (...
DirectX_Programmer's user avatar
1 vote
1 answer
392 views

Importance sampling of the blinn-phong brdf in pathtracing

tl;dr: How do you importance sample the blinn-phong-brdf? Recipe for importance sampling of the phong brdf as far as i understood it (pseudo-code): ...
Berti Krüger's user avatar
1 vote
1 answer
2k views

How can I send custom bitmap to frame buffer?

I was trying to make a CPU-based ray tracer but I know after all the calculation I will end up with an array of pixels. I don't know how to paint it on the screen. What are the various ways to do that?...
videogamechef's user avatar
1 vote
1 answer
659 views

Monte Carlo Importance Sampling

I am following the "Ray Tracing - the Rest of your Life" book by Peter Shirley and I am facing some troubles in the implementation of Monte Carlo importance sampling, and Direct light sampling. Monte ...
maurock's user avatar
  • 189
0 votes
1 answer
995 views

Tone mapping bright images

I am rendering the sun in an image, and the sun comes out white and is basically very unrealistic. I have tried searching for tone mapping algorithms but I'm very lost. Can someone guide me to do ...
Maria's user avatar
  • 11
0 votes
1 answer
469 views

Raytracing in OpenGL or Vulkan?

I was looking at this glass ball rendering with an image inside of it (zoom out to see the glass ball), and noticed that it looks like they simulate the refraction of light as it crosses from inside ...
HelloGoodbye's user avatar
0 votes
1 answer
2k views

Transforming a ray from camera space to world space

I am writing a Raytracer and generating rays from the camera. I have a working program but slightly confused about the linear algebra concepts involved in transforming the ray from camera space to ...
Sahil Gupta's user avatar