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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1answer
45 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
65 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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49 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
58 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
49 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
98 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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41 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
68 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
83 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
87 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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0answers
83 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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55 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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37 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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0answers
44 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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74 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
96 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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0answers
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
48 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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0answers
28 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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0answers
33 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
124 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
110 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
68 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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2answers
112 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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0answers
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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1answer
117 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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0answers
33 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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34 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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24 views

Computing inverses in Reversible-Jump Metropolis Light Transport

Say we are sampling a path $\rm x=(\rm x_0,\ldots,\rm x_{n-1})$ of length $n-1$ using bidirectional path tracing. Let $p_s$ denote the area product density corresponding to the used connection ...
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71 views

Ray Tracing -Weird Edge Artifact

I am interested in Path Tracing, I currently follow the Ray Tracing in a weekend book. When implementing the metal material, I get a strange artifact on the edge of the sphere that does not appear in ...
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1answer
109 views

Retrieve real distance from depth buffer for shadow ray (vulkan hybrid rendering)

I'm trying to implement an hybrid renderer based on Vulkan extension VK_NV_ray_tracing. Basically, the rasterizer compute the albedo and depth map of the scene. Then I try to compute the distance from ...
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1answer
54 views

In bidirectional path tracing, is a camera subpath with $n$ vertices determined by a fixed number of random numbers?

In the Multiplexed Metropolis Light Transport implementation of the book Physically Based Rendering, the proposal samples are generated by the Primary Sample Space Sampler ...
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2answers
127 views

Why is my raycaster so slow?

I'm trying to write a raycaster similar to Voxlap, but it's many times slower. I've tried octrees, but the performance gains are marginal- only 10 to 20 percent. I use the algorithm from this site: ...
4
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1answer
144 views

What is a “light source” in global illumination?

In the context of global illumination and the scattering equation, do we need to understand "light sources" as surfaces with a "purely emissive" material on which no scattering is present? In ...
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0answers
50 views

Implementation of the Primary Sample Space Sampler in the book Primary Sample Space Sampler

In the Multiplexed Metropolis Light Transport implementation of the book Physically Based Rendering, the proposal samples are generated by the Primary Sample Space Sampler ...
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0answers
21 views

How do I render from chunks?

I'm trying to implement chunks/octrees to speed up my rendering times. However, objects sometimes disappear, and it segfaults or hangs frequently. Full code: https://pastebin.com/4P3sX6BV - main....
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1answer
42 views

Mapping sample to a disk

So I have been reading this wonderful book on ray tracing by Kevin Suffern, Ray tracing from Ground Up. I am reading this book after finishing Peter Shirley's first two book on ray tracing & ...
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1answer
87 views

How can I raycast with chunks?

I am attempting to implement chunks/octrees to speed up my render times. However, sometimes the walls show horizontal or vertical lines (rays hitting the inside of voxels?) or some blocks disappear ...
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0answers
32 views

Can solid voxelization be done with 1-direction raytracing if the raytracer is watertight? Does the direction matter?

This article and some others mention requiring the following when voxelizing: 1: Shooting rays from multiple directions (maybe with a voting system to decide if the voxel is active?) 2: Shooting ...
2
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1answer
47 views

How to decide which child of BVH to visit based on sign of ray's direction vector?

I'm reading about BVH from PBRT. According to the book, in the linear bvh part using morton encoding: An efficient way to perform a front-to-back traversal without incurring the expense of ...
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0answers
142 views

Strange behaviour when tracing rays through hemisphere patches

I have implemented a ray tracer using reinforcement learning. But I see some problems. I tried to divide the planes into rectangular grids. I searched the moire effect and realized that I can solve my ...
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1answer
97 views

A pseudocode to parallelize a path tracer?

Where can I find a pseudocode to parallelize a path tracer using multiple cpu threads? How should I change the normal path tracer to be capable of parallelization?
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0answers
72 views

What is the name of this effect and how could I solve it?

I've implemented the algorithm in the paper "Learning the light transport the reinforced way". What is the name of this effect and how should I solve it?
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1answer
89 views

What is the PDF for path tracing in the paper "Learning the light transport the reinforced way

It's the algorithm which combines path tracing and reinforcement learning. I can't understand what $p_\omega$ is. The algorithm is clear. The actions are the directions and the states are the hit ...
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0answers
40 views

Temporal anti-alliasing breaks the entire image

I'm kind of lost here as I'm faced with a graphical bug the origin of which I don't even know. In an attempt to recreate a shadertoy I saw that had TXAA, I made a function TemporalAA that takes in 3 ...
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4answers
235 views

Why isn't rasterization combined with raytracing more often?

If I'm not mistaken, you can make a hybrid renderer which lets a rasterizer solve the visibility problem, then shade all of the projected shapes with a raytracing algorithm. It seems that this isn't ...
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2answers
76 views

Inverted Normals in Raytracer

I am having the following issue. I am working on a ray tracer for school and I am trying to render a sphere where the radiance of a intersection point is the dot product of the ray direction and the ...

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