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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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14 views

How does multiple importance sampling work and how should I generate the samples?

Is my understanding of MIS algorithm true? I first generate a random number $x\in U(0,1)$ and $w_1=\frac{p_1(direct)}{p_1(direct)+p_2(hemisphere)}$, and then if $x < w_1$ generate the sample ...
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1answer
35 views

How can I implement next event estimation?

I am trying to implement next event estimation to reduce the noise of path tracer and I need a pseudocode. Edit: I know how to sample direct illumination but the visibility function is the real ...
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32 views

Oren-Nayar Reflectance

I'm trying to implement Oren-Nayar reflectance and I don't quite understand the Wikipedia article on it. In the article, it has this diagram: I can't figure out what $(\theta_i, \phi_i)$ and $(\...
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47 views

Implementing GGX VNDF importance sampling with DXR

I am currently implementing the GGX specular BRDF in a DXR raytracer using the importance sampling method describe by Heitz I am sampling the VNDF with: ...
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49 views

Why does my julia ray tracer return stack overflow error?

I' trying to write a monte carlo ray tracer in julia, but my main function returns stack overflow error. Below is my main function: ...
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21 views

Report standard deviation in Rendering results

I noticed that a common metrics for image quality assessment (Monte Carlo path tracing) is MSE between the generated image and a reference one. My question is: why isn't the standard deviation ever ...
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1answer
38 views

Calculate Normals of Boolean Operation for Ray Tracer

I'm working on a small ray tracing project in my free time and I'm currently implementing boolean operations for spheres. My code is setup to calculate the intersection points of each of the spheres ...
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56 views

Color shading and light calculation for ray tracing

I am currently building a ray tracer and I came across a problem and confusion regarding the light calculations. For lighting, I am using the following mathematical model: Where ...
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39 views

Multiple Importance Sampling in Bidirectional Path Tracing

I'm trying to understand the computation of the path density described in the book Physically Based Rendering. They assume that a path $$x=(x_0,\ldots,x_{n-1})=(q_0,\ldots,q_{s-1},p_{t-1},\ldots,p_0)$$...
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26 views

Probability of choosing the current strategy in the pbrt implementation of Multiplexed Metropolis Light Transport

In the description of the Multiplexed Metropolis Light Transport implementation of pbrt it is claimed that "the inverse probability of choosing the current strategy $(s,t)$ [...] is equal to <...
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43 views

Weird Ray tracing artifacts when Code run on widows

I am trying to create a raytracer following peter shirley's in a weekend series. I am getting weird color distortion artifacts when I am running the code on windows. However, the code runs fine when ...
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33 views

How to display image from CUDA / What API to port my project to for real-time raytracing?

I started a raytracing project using the python numba library which provides a just-in-time compiler for CUDA kernels. When the scene is rendered my result is a 1920 x 1080 x 3 RGB array in GPU memory....
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78 views

Compute shader only 5 times faster on the GPU than on the CPU

I'm running following compute shader in Vulkan. worldImage is device local memory that holds the world. resultImage is reference to the memory of the swapchain image: ...
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2answers
70 views

Diffuse lighting calculations in ray-tracer

I am trying to write a ray-tracer. The lighting part is proving to work but not accurately. To debug I simplified the scene to a single sphere centered at the origin with a radius of 1 and a point ...
2
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1answer
53 views

Strange sphere reflection effects in ray tracing project. I cannot figure out what causes them

I started a ray tracing project in Python. I made a CUDA kernel and a trace() function for each pixel. It works perfectly when calculating intersections, shadows and lambert shading, however when I ...
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84 views

Proper way of consuming stratified samples in path/ray tracing

I'm working on a (toy-level) path/ray-tracer, currently trying to implement (and understand) improved sampling strategies. The obvious next choice after uniform random sampling would be stratified/...
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80 views

The termination probability of Russian roulette in PBRT

As described in PBRT 14.5, the path tracer stops bouncing rays at a probability q, which is determined by the throughput of the path. ...
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1answer
114 views

GLSL Compute Shader doesn't run for large inputs

The shader takes an SSBO of Photons that have a position, direction, wavelength and intensity and each thread is responsible for tracing exactly one photon through the grid, where at each grid cell ...
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1answer
102 views

Regular voxel grids and RTX accelerated ray tracing

I've been looking to play with ray tracing, starting with a simplest of minecraft clones (making something more akin to cave game, for starter). I figured I'd define a voxel as a primitive and then ...
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1answer
43 views

Physically realistic received irradiance values given some BRDF?

I am trying to simulate the actual response of a camera given some object that is reflecting light. I've written a ray tracer, and have a BRDF that I need to use, and I have a camera sensitivity in ...
2
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1answer
69 views

Offline path tracer produces a darker image than expected

I've been going though Peter Shirley's beginner raytracing books. Upon building the Cornell box and rendering an image, I get a much darker / dimmer image than expected. The color values are ...
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42 views

Moving a sphere in a basic ray tracer

I have written a really basic ray tracer. It generates primary rays and sets the colour of the pixel to the colour of the object that I have set myself. The code for which can be seen below. ...
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41 views

Reddish tint with spectral renderer

I'm trying to implement a spectral path tracer and comparing results from my program with renders of the same scene done with pbrt and ...
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3answers
101 views

What is the purpose of the projected solid angle $dA^\perp$ term in the definition of Radiance?

In the definition of Radiance, which according to PBRT is defined as flux per unit solid angle $d\omega$ per unit projected area $dA^\perp$ $$L_i=\frac{d\Phi}{d\omega\ dA^\perp}$$ My original ...
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1answer
108 views

Tone Mapping in a physically based rendering ray tracer

I'm implementing a pbr ray tracer. Let's say that I'm at the end of the process: for each pixel pi, I accumulated the radiance value in vector pi = (radR, radG, radB). At this point, these values are ...
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61 views

Using octree for cheking intersection of ray and meshes

I wrote the code for checking intersection of ray and meshes on scene. It consist of two parts - broad phase and narrow phase. In broad phase I build an oriented bounding box around each mesh and ...
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1answer
89 views

Dealing with interpolated normals within a raytracer

I am trying to render a teapot within a simple raytracing that can handle reflection, refraction, and shadowing from point and directional lights. I am very confused about one detail of the raytracer ...
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1answer
111 views

Camera Model View transformation in Ray Tracing

I am implementing my own simple ray tracing and I came across some sort of confusion. When defining the verticies in the world I multiply them by the modelView transformation system (the matrix ...
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1answer
77 views

how many watts are in the SPD of the color white?

Please help. I'm trying to implement a ray tracer, going by the PBRT book and got stuck on an issue that I fail to find the answer to. My scenes are made from objects and light sources. From that, I ...
4
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0answers
116 views

Learning light transport using Q-Learning

I am trying to reproduce the results obtained by Dahm et al. in the paper Learning Light Transport the Reinforced Way. This method takes advantage of the similarity between the Bellman equation (Q-...
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1answer
164 views

Why the ray tracing result looks weird?

I followed the book Ray Tracing in One Weekend and implemented a simple ray tracing procedure. There are 100 random samples every pixel for antialiasing, but the render result looks weird: There is a ...
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1answer
98 views

Unsolved Problems in CQ to this day?

What problems haven't been solved yet when it comes for instance in rendering,deferred rendering, Volumetric lighting, ambient occlusion or in any other interesting area. When i say unsolved problems, ...
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1answer
101 views

Why is it easier to inverse transform every object in a scene than to transform a camera?

My lecturer for a computer graphics (raytracing) paper has stated that 'It is easier to apply the inverse transform to the world than it is to apply the transform to the camera.' The example given was ...
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1answer
134 views

smallpt: ray scattering and Importance Sampling

Introduction For those familiar with smallpt by Kevin Beason: In path tracing, when rays hit a surface, they are scattered and the theta angle (the angle between the normal to the surface and the ...
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1answer
92 views

smallpt: when to stop diffuse ray scattering

For those familiar with smallpt, the ray tracer in 99 lines: I am checking the code, and there is something that is not clear to me in the DIFFUSE ray scattering. After the rays are shot, they keep ...
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180 views

How to account for self intersection with large ray tracing scenes?

I'm working on a hybrid real time ray tracing project and trying to tackle the problem of self-intersection with larger scenes due to loss of float accuracy. The logic I'm trying to use is based on ...
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1answer
161 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 ...
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1answer
121 views

How to simulate a line laser diode?

I'm interested in simulating the way a laser line deforms when it strikes an object and runs along the surface of it. Which concepts would be involved? Is there any 3D modeling software out there that ...
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2answers
118 views

What is a list of common, cheap, real time rendering algorithms?

I am well aware of the existence of Blinn-Phong shading, which is a great tool when you are doing, for example, modelling algorithms and wan't to focus on the model. In this case a full BRDF result, ...
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1answer
90 views

Ray tracing the next week: understanding Instances

My question is not about the code, but it's about the approach used by the author Peter Shirley (and apparently common practice in ray tracers) of handling Instances. To understand the question it's ...
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1answer
168 views

Ray tracing in One weeked: issue with metal reflection

Problem I am following the book Ray tracing in one weekend , and I got stuck after the implementation of the material Metal. I checked my code many times, and it looks exactly like the code ...
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2answers
153 views

How to set equivalent PDFs for cosine-weighted and uniform-sampled hemispheres?

I'm trying to add BRDFs to a very basic path tracer. Starting out, I'd like to convert just the Lambertian material, with two different sampling methods, to ensure that everything is working right. ...
2
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1answer
254 views

Bump mapping with triangles and height maps

I'm trying to add bump mapping to my ray tracer, and I'm currently struggling to add bump mapping to it, as I don't seem to get the transformations from texture space to world space correctly. I have ...
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3answers
490 views

How to calculate ray

In ray-tracing technique critical point is to calculate rays which came out from eye $E$ to target $T$ through pixel $P_{ij}$ on viewport. The "viewport" is represented as rectangle divided to square ...
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1answer
544 views

Get intersection Ray with square

I have a class Ray and Square public class Rayo { public Point origen; public Vector direction; Square{ X,Y,Widht, height; } I need intersection between this ...
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1answer
102 views

Rendering Equation for photons carrying flux

I am trying to understand the mathematical/physical foundations of photon mapping better. In the forward photon tracing step it is established, that the rays are carrying portions of total power (...
2
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1answer
286 views

How do I convert a hit on an infinite plane to UV coordinates for texturing in a Raytracer?

I am trying to convert a ray hit on an infinite plane, defined by an origin and a normal vector, into UV coordinates, so I can find the appropriate texel at that point. Code I have is close to ...
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1answer
122 views

“Artist Friendly Metallic Fresnel” reversible?

While implementing the "Artist Friendly Metallic Fresnel" paper by Ole Gulbrandsen (http://jcgt.org/published/0003/04/03/paper.pdf), I read that it is fully reversible: (section 2.3.2): for all r,g ...
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2answers
103 views

Writing data to a shader resource at runtime in DX12

I'm hoping to port my existing toy raytracer to a window so that I can see samples accumulate over time. And then port over to Pixar's pmj02: https://graphics.pixar.com/library/...
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23 views

How to rotate camera in CAD package application

I can rotate camera to change the view for the first person. But as I am working on a camera object for a cad package this isn't a first person or walk-through. I am not sure how to rotate the camera ...