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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59 views

Pathtracing - many bounces reduce shadows

I'm creating DXR PathTracer highly influence by Matt Pettineo's one - https://github.com/TheRealMJP/DXRPathTracer ; Relevant HLSL code below: ...
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1answer
54 views

Importance sampling GGX NDF - fireflies and bright final result

https://schuttejoe.github.io/post/ggximportancesamplingpart1/ - I have problem implementing this method. Somebody asked question about this before ( Can't understand the Importance sampling GGX ) ...
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1answer
42 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 ...
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1answer
46 views

Importance sampling a cosine distribution

Let's take a look at this blog article - https://schuttejoe.github.io/post/ggximportancesamplingpart1/ and image presented as a result of implementing it: Inside above link, you can see description ...
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1answer
82 views

Why does my image has a square pattern in cuda path tracer?

I am writting a path tracer in cuda following the Shirley's book. I am having a square pattern as an output. The size of the block change if I change the block dimensions. For this image, the block ...
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1answer
73 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 (...
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1answer
48 views

Worsening sampling quality of raytracing with increasing distance from world origin

I am using RT shader (DXR) to generate g-buffers with code below. There was no problems with smaller scene (pink room from cwyman tutorial - http://cwyman.org/code/dxrTutors/tutors/Tutor5/tutorial05....
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1answer
60 views

What should I do when a new sampled direction is below a normal oriented hemisphere?

I generate random directions from the pdf of D term in GGX BRDF. On the picture, white dots are new directions and the cross is the light direction, with roughness = 1. What should I do with the ...
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29 views

Global root signature crash

I have a problem with RTPSO creation. Using local root signatures for each of rgs (ray generation shader), chs (closest hit), miss is working correctly. However, for performance sake, I want to use ...
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0answers
75 views

BVH works fine, but why does it slow down a lot when using Cornell Box? How to improve it?

I am using the SAH-BVH from PBRT-v3, it works fine for triangle-mesh, especially for dense mesh. But here is a problem. If I added Cornell box while building the BVH tree, the BVH performance will ...
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2answers
98 views

Ray Tracing, why does the GGX make my rendering result darker and darker for each frame?

I am trying to add GGX and PBR textures to my GPU ray tracer. The result is very strange, it's getting darker for each frame. ...
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1answer
70 views

Raytracer help - Background color writing over some colors?

I'm implementing Peter Shirley's "Raytracer in a Weekend: The next week" and I'm having some trouble with rendering a scene with a light. I'm not sure if the issue is the background color or ...
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1answer
34 views

Hit group - export already defined

I am getting this error when creating RTPSO with multiple hit groups: ...
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41 views

Euclideon Unlimited Details Voxel Engine Architecture

As I understand Euclideon haven't just rendered voxels for these infamous demos, since the amount of geometry is still too large for the 2010 PC with software raytracer and the model taking whole HDD ...
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24 views

How does one obtain SDF of an octree?

As I understand the usual practice is to obtain the SDF by the means of a KD-tree. But the KD-tree generation and the lookup (for each ray step) are, well, slow, while the octree can be easily ...
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1answer
47 views

Texture value clamped to 1

I am working on ray/path-tracer using DXR and I'm starting with simple AO. In first pass, I am storing normal value and RayTCurrent(): ...
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2answers
182 views

Is BVH faster than the octree/kd-tree for raytracing the objects on a GPU?

Apparently most people use BVHs in their raytracers. The ray-AABB intersection code is very fast and and the BVHs also compresses empty space efficiently, working even with infinitely large objects, ...
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2answers
261 views

Why is eye-based ray tracing preferred over light-based ray tracing?

It seems that virtually all path tracers use eye-based or view-based path tracing. That is, the light rays originate from the camera rather than the light source. The reason given for this everywhere ...
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45 views

What's a good research topic in Computer Graphics?

I am currently trying to find topics for my master's thesis. I would really like to do something in the field of computer graphics, but I've been having trouble finding what are some current problems ...
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1answer
58 views

Rendering moist/wet materials like human anatomies for surgical simulators

Real human anatomies look wet/ moist when operated. I am looking for some good methods for rendering anatomies in a virtual simulation, and hence I have done a literature survey on 'Rendering wet ...
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1answer
71 views

Math for adaptive supersampling for raytracing

How do I determine how many (jittered) rays to trace for a given pixel, as a function of the statistics of a small initial set of test rays? Also, what size should the initial set be? (it's currently ...
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0answers
53 views

Implementing monte carlo path traced refractions problem

I am writing a forward monte carlo path tracer with the added feature of specular refractions for transparent materials, I have managed to come this far but something is not quite right and I am ...
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1answer
60 views

Ray Tracing Bounding Volume Hierarchies nodes

I'm new to computer graphics programming so I apologize in advance if my question is stupid. I'm trying to implement a BVH for my ray tracer and I looked at some lectures explaining BVH. They all ...
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2answers
51 views

Weird patch on reflective spheres on planes in raytracer

I am writing a small raytracer in python , everything was working fine but when i implemented plane geometry then the reflective spheres are getting weird patches on lower bottom. image below: I ...
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1answer
111 views

Prove radiance contributions of deeper paths fade away

When ray tracing, I find it intuitively clear that deeper paths have a lower contribution to the overal picture than shorter paths. This is the main reason why it is generally okay to render a picture ...
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51 views

Why is my ray caster is running much faster as a fragment shader compared to a compute shader

I'm trying to write a simple ray caster in OpenGL with C++. Previously, I have been using the fragment shader of a quad that covers the entire screen to do all the ray calculations. Now, I want to do ...
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1answer
95 views

a very simple raytracer is giving a black output which is implemented in python

I am trying to implement a simple raytracer in python. I am following this tutorial here here is my code, i have explained in comments the relevant parts .All i am getting is a blank image. ...
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2answers
101 views

Understanding of Microfacet monte-carlo path tracing

I am trying to implement BRDF microfacet path tracing and I think I need a little push. I will explain what I understand so that you can correct my mistakes. I start with simple rendering equation: ...
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1answer
120 views

Feeding acceleration structure to the GPU then raytracing it in a compute shader?

I want to use Vulkan's rasterization to solve for the visibility problem, but once that is done I want to do shading, reflection and transmission through a raytracer which also runs on the GPU. With a ...
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88 views

Visualize the variance of an image

Let $h_j$ denote the image reconstruction filter of pixel $j$. I'm estimating the color value $$I_j=\int h_jf\:{\rm d}\mu$$ of the $j$th pixel (see [Veach, Section 8.2]) by an asymptotically ...
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57 views

How do I produce a metallic surface in ray tracing?

I can't manage to produce a metallic looking sphere despite trying many things. I have the basics working, i.e shadows, refraction etc. but I'm not sure what combination of these will allow me to ...
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41 views

How to handle negative reflection directions in raytracing?

I got a function that generates samples from a GGX visible normal distribution function. When I use it to calculate reflection directions obviously some of these intersect with the surface agin (...
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53 views

Considering a path generated by bidirectional path tracing under a different strategy

Say I have constructed a path, using bidirectional path tracing (BDPT), consisting of a light subpath $y$ with $s=2$ vertices and a camera subpath $z$ with $t=3$ camera vertices. Now I want to ...
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45 views

How is the image reconstruction filter on the path space defined in terms of the filter on the raster space?

Say we have a image reconstruction filter $h:R\to\mathbb R$ defined on the raster space $[0,w]\times[0,h]$, where $w,h\in\mathbb N$ define the width and height of the image plane in pixels, ...
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76 views

Relation between camera sensor responsivity and image reconstruction filter associated with a pixel

Let $W_{\text e}$ denote the camera sensor responsivity (i.e. importance) and $h_j$ and $W_{\text e}^{(j)}$ denote the image reconstruction filter and sensor response associated with the $j$th pixel, ...
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1answer
112 views

Properties of the image reconstruction filter in rendering

Let $f$ denote the measurement contribution function for paths of length $k\in\mathbb N$, i.e. $$f(x)=g(x_0\leftrightarrow x_1)W_{\text e}(x_1\to x_0)t_k(x_0,\ldots,x_k)L_{\text e}(x_k\to x_{k-1}),$$ ...
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134 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 ...
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1answer
50 views

Determining shortest vector between a ray and an axis-aligned 3D bounding box (correcting a near-miss)

I have a situation where (due to floating point error) a ray that is known to hit a bounding box fails due to floating point error. (1e-8 or so) Expanding the box is not an acceptable solution in my ...
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30 views

Quantify the variance of pixel measurements

Say $E_j$ is an estimator of the value $$I_j=\int f_j\:{\rm d}\lambda$$ of the $j$th pixel given by the path space integral of the corresponding measurement contribution function $f_j$. $f_j$ is of ...
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36 views

Is casting a shadow ray non-symmetric in pbrt?

According to the description in the book, Scene::IntersectP() "checks for the existence of intersections along the [passed] ray". This operatorion should be ...
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1answer
154 views

Which technique should be used for rendering under water images, Ray tracing or Radiosity?

Rendering is the process of computing a three-dimensional geometric description of a scene into a two-dimensional image representation that looks real. Ray-tracing and Radiosity are two of the most ...
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2answers
113 views

Need a fast ray-box intersection that handles if a ray is parallel and in line with a plane of the box

I've seen lots of spins on the ray-box intersection test, and a lot of them seem to boil down to this code: (omitting some details here) ...
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1answer
86 views

Reading thesis on cone tracing, did the author make a mistake?

I am reading this document that talks about signed distance field rendering. In that document section 6.3, on the topic of cone tracing, it says: Cone tracing is an extension of the sphere tracing ...
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1answer
155 views

Ray vs AABB algorithm that also gives which side was hit?

There are plenty of well-known algorithms for determining if a ray hit an Axis-Aligned Bounding Box (AABB), like Andrew Woo's covered in a response here. Using ...
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48 views

Subpath connection in Bidirectional Path Tracing for subpaths consisting of a single vertex

Consider the PBRT implementation of the subpath connection in bidirectional path tracing for the strategy with a single camera vertex, as described here: http://www.pbr-book.org/3ed-2018/...
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141 views

Confusion around Lambert's Cosine Law in Ray Tracing in One Weekend

Peter Shirely's Ray Tracing in One Weekend presents the following function to calculate the color of a lambertian material (See chapter's 7 and 8): ...
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47 views

Distribution of the first vertex on a camera subpath in bidirectional path tracing

Suppose we are sampling camera rays of a perspective camera with a finite aperture. The PBRT implementation of the sampling scheme looks like this: ...
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34 views

Computing probabilties when connecting a camera subpath to a single light point

I'm struggling to understand how the connection step in bidirectional path tracing for the strategy with a single light vertex has to be implemented. The following code essentially shows the PBRT ...
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0answers
47 views

Chart swaps and path inversion in bidirectional path tracing

I've got a hard time to understand how we would implement the following in practice. I'd be great if someone could explain the details for the example below. Assume we're generating a path ${\rm x}=(\...
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35 views

Inverse path sampling in (bidirectional) path tracing

In Section 4.1 of the paper Fusing State Spaces for Markov Chain Monte Carlo Rendering, it is described that the CDF $P$ of the distribution of paths of length $k\in\mathbb N$ may be factored into a ...

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