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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Is there a way to force a closest hit shader?

I want to add a debug feature to my ray tracer (runs in both Vulkan and OptiX). For that, I'd like to switch all objects to use a specific closest hit shader. Can I do this? I have only found the ...
Tare's user avatar
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Understanding the BRDF Equation

I am studying the BRDF equation. From Wikipedia, the equation is as follows: I have one main question: Where does the $\cos{\theta_i}$ in the denominator come from? The denominator implies that $...
Christopher Miller's user avatar
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Evaluating the Rendering Equation by hand (simple case)

I'm trying to make intuitive sense of the rendering equation and so I'm trying to work out a trivial example by hand, though ultimately I'm just trying to understand how monte carlo importance ...
Chris Gnam's user avatar
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Vulkan (Hardware) Path Tracing Formulation

I've been implementing a path tracer in Vulkan using the VK_ray_tracing extension and am a bit confused on how to set up the pipeline. Currently I've been following the style of the Reference Path ...
sshashank124's user avatar
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How do I access vertex buffers corresponding to different (bottom level) acceleration structures?

I want to render scenes like they are used in mitsuba or pbrt (see https://benedikt-bitterli.me/resources/ for example scene description files). That is, I have a list of obj-files. Each Obj file ...
0xbadf00d's user avatar
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Problems with distributed ray tracing and particle system

based on the ray tracing stunning effect, I'm considering a resilient distributed ray tracing implementation, I've just finished a basic computer graphics course, and I'm currently working on directX ...
Haitao Xiao's user avatar
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Blin Phong BRDF in an unusual coordinate system

a happy New Year to everybody! But, a new year means a new question: In my problem, a mirror is placed in a vertical position, i.e. along the z-axis.The x- and y-axis are perpendicular to this axis. ...
Uwe Nass's user avatar
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Lambertian surface and the luminous intensity

I am currently studying the basics of photometry to better understand the rendering equation of Kajiya. One thing I'm currently struggling with is Lambert's cosine law. Let's go over the premises: A ...
Bartolini's user avatar
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Ray Tracing in Camera-World Space

I am trying to implement rendering in "Camera-World" space following PBRT-V4's camera implementation in my Rust ray tracer. I Have been trying to solve that for days I read these multiple ...
AregevDev's user avatar
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Confusion about different sampling strategies in Monte Carlo Path Tracing

I am studying Monte Carlo Path Tracing from different sources. However, I have some confusion about the sampling part and dare to post here for experts' ...
bim's user avatar
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How to imlement the Phong BRDF

I'm really sure that this question was asked before, and I found some code snippets by searching this via google. Unfortunately these snippets are in openGL or some other high level computer graphics ...
Uwe Nass's user avatar
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What is the difference between Uniform/Storage Buffer and Hitgroup Record data buffer?

I have a vulkan ray tracer in which I uploaded my vertices as a single buffer (for all meshes in the scene) as a storage buffer. I have one closest hit shader per way-of-calculating-lighting (e.g. one ...
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Why would an image look the same pre-raytracing and post-raytracing?

I am trying to raytrace an image of a black hole, but given my current difficulties of doing so with the formalism of relativity, I've decided to do my raytracing using Newton's law of gravitation ...
JS4137's user avatar
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Why doesn't using depth biasing to fix shadow acne result in an even bigger problem?

I am currently reading the Ray Tracing in One Weekend tutorial (link), and I am dubious about their fix for shadow acne, which is to ignore ray-geometry intersections that occur at very small times. ...
Christopher Miller's user avatar
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3 answers
138 views

How to calculate the radiance of the reflected light ray using the Blin Phong BRDF

to get the radiance of the Lambertian diffuse reflected light, I have to multiply the constant pdf (rho/pi) with the incoming intensity I0*cos(theta_i), where cos(theta_i) is given by the scalar ...
Uwe Nass's user avatar
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Precision errors with raytracing normal

I'm writing a raytracer in Java that draws a scene containing the elliptic paraboloid defined by the equation $F(x,y,z)=x^2+z^2-y=0$, as well as the hyperbolic paraboloid defined by $G(x,y,z)=x^2-z^2-...
zenzicubic's user avatar
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Can raytracing be used to determine a certain gas distribution in a real planet's atmosphere?

I want to calculate the capacity that the planet Mars has regarding protecting against UV-light for a final project I will be doing my last year in upper secondary school. UV-light is mainly absorbed ...
Josefin's user avatar
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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
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1 answer
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What is out-of-core raytracing?

I just stumbled upon this "out-of-core" term and tried to see what it is about. There are a few papers and even a few questions talking about it here at computergraphics.stackexchange, but I ...
Tare's user avatar
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Where does sin(theta) go in estimators of The Rendering Equation?

Consider this equation, where we have a surface integral over hemisphere with Lambertian BRDF and cos(theta) from The Rendering Equation: $$ \int_{0}^{2\pi}\int_{0}^{\frac{\pi}{2}}\frac{albedo}{\pi}...
Ocelot's user avatar
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Defining ray direction vector

Here I try to combine scratchapixel's articles to understand the operation of the camera-to-world matrix and ray direction vector. Here https://www.scratchapixel.com/lessons/3d-basic-rendering/ray-...
Zhenya Karapetyan's user avatar
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What is this cardioid/fish-like graphic that appears in FFXVI when looking at the sun?

In Final Fantasy 16, a recent video game, when looking towards the setting sun, one sees several circles, which seem like the lens flare that one commonly sees in games. But the most prominent (circle)...
chausies's user avatar
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Motivation for densities wrt the same measure in MIS

In Veach's thesis the MIS weights (e.g. using the balance heuristic) for two strategies with densities $p_1, p_2$ are given as $w_1(x) = \frac{p_1(x)}{p_1(x)+p_2(x)}$ and $w_2(x) = \frac{p_2(x)}{p_1(x)...
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How many rays can one RT core calculate simultaneously?

I have noticed that all GeForce RTX cards, without exception, have an equal number of RT cores as they have streaming multiprocessors (SM). From this fact I assume that each RT core is associated with ...
Warp's user avatar
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Raytracing Diffuse Function not Working as Expected

I am trying to write a raytracing renderer using compute shaders in Metal. My implementation is based off of Peter Shirley's Raytracing in One Weekend: https://raytracing.github.io/books/...
oli2's user avatar
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Calculating world coordinates of a pixel from a camera picture

Sorry for this question. I know there are many similar questions but I really know nothing about math that involves this case. I have a picture taken from a camera. I know some information about this ...
Magno C's user avatar
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How to properly use the BRDF from glTF 2.0 specification in path tracing while using metallic/roughness materials?

I've built a renderer which should render glTF materials, as they are defined in their specification. So I should be able to render satisfying (similar to Cycles and Ospray) results just from the base ...
AllenTeehrsie's user avatar
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Ray light color at distance

I am obviously not understanding something related to light for a ray tracer. Reading Spectral representation and Point light calculation A bit of a context: My question is: in room at X degrees ...
LeXav's user avatar
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How does Unreal Engine 5's Lumen (most likely) implement reflections?

In this YouTube video, the creator mentions that reflections in Unreal Engine 5's Lumen "work by tracing the path of light as it bounces off of surfaces in the game world." Does this mean ...
HelloGoodbye's user avatar
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1 answer
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How to compute discrete partial derivatives in 3D

I'm supposed to compute partial derivatives for 3D volume rendering (in ray tracing). I'm bad at math and so I can't understand what $f$ is in my case. In reviewing examples, I'm seeing the $f$ ...
Mote Zart's user avatar
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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
1 vote
1 answer
77 views

convert right handed matrix into left handed forward/up/right vectors

I have an openGL style matrix (column major, right handed ) that needs to be converted into two vectors (forward and up) I've managed to find, in a weird way, a solution that matches the the ...
ytrox's user avatar
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1 answer
157 views

How is Aperture and Pixel Size accounted for in calculating received power using ray tracing?

NOTE: Deleting the question to rephrase it after continuing to read other responses and toy around with it: I've written a path tracer and am now working on implementing a physically accurate way of ...
Chris Gnam's user avatar
1 vote
1 answer
152 views

Converting points, vectors, normals between world and object space for a ray tracer gives weird results

I'm writing a ray tracer but having trouble converting rays and normals between world space and object space. I am creating a Ray, then transforming it with transformation matrices, calculating ...
Cedric's user avatar
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4 votes
2 answers
220 views

cosine term in rendering equation

Rendering equation's value can be estimated with Monte Carlo (Physically Based Rendering: Light Transport I: Surface Reflection): $\begin{equation} \begin{split} L_o(p, \omega_o) &= \int_{S^2}f(p, ...
Rahn's user avatar
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Porting from DXR/HLSL to Vulkan Ray Tracing Extension/GLSL

I am working on the port of a demo from DXR to Vulkan Ray Tracing extension using GLSL. In DXR/HLSL space, there are RayTMin() and RayTCurrent() functions to retrieve the starting and the current end ...
Vectorizer's user avatar
1 vote
1 answer
105 views

Missing triangles when rendering with BVH

I'm writing a software ray-tracer. I implemented a BVH structure (octree, actually) and traverse algorithm, but when I use it I get missing triangles. These are the facts that I have: Rendering ...
andre_ss6's user avatar
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2 votes
2 answers
151 views

Glowing objects in a raytracer? How it works?

My raytracer has a point light source, it works as it should, illuminates the scene, but there is a problem, it is not visible, I would like to add glowing objects to the raytracer, for example a ...
LINUX_ADMIN's user avatar
1 vote
1 answer
151 views

Rendering equation integration variable change

I'm watching the TU Wien rendering lectures in the course we were presented with a rendering equation (first one on the screenshot) and then another, which results from a change of variables (if I ...
analysis1's user avatar
3 votes
2 answers
407 views

ray-box intersection

I've searched everywhere for an equation that suits my needs but i couldn't find anything useful. I'm making a voxel ray-tracer so I need an equation that gets me the intersection of a ray with a box, ...
Not Gartificial's user avatar
1 vote
0 answers
189 views

Calculation of reflection vector in Phong specular lighting

I wrote the following phong reflection model for ray tracing in Rust, but I am not sure about the calculation of a reflection vector for the specular reflection. ...
user48423's user avatar
1 vote
0 answers
97 views

Calculating ray intersection with two spheres (with smooth_blending between the two spheres to make them appear as one continuous geometry)

I have the following function to define the distance to the interesection between a ray and the surface of a sphere: ...
Iron Attorney's user avatar
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Trouble getting a raytracer camera representation for different aspect ratios

I am trying to make my camera representation work for images whose aspect ratio isn't 1 (640x480, 1920x1080...), but I am having some trouble getting it to work. The camera model is pretty simple, as ...
Lightsong's user avatar
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Is this algorithm a variation of ray tracing worth something?

Im not a professional computer graphics programmer, I'm just learning. All the tutorials I've seen so far about ray tracing have one thing in common, that in order to get good visual results they need ...
Robert Puscasu's user avatar
1 vote
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61 views

Question about reconstruction filter in ray tracing?

Suppose we have an 512x512 image, then the value of pixel j should be $I_j = \int_{0}^{512} \int_{0}^{512} h_j(u,v)L(u,v) \,dudv$, where $h_j(u,v)$ is the filter function for pixel j, $L(u,v)$ is the ...
Andy's user avatar
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Tracing conic surface through voxel grid

I have a voxel grid and a conic surface (hollow cone) placed in the grid. I want to know which voxels intersect with the cone surface and how much. So far I have tried sampling points on the conic ...
Vojtooo's user avatar
1 vote
0 answers
150 views

MIS path tracing got darker image than brute force path tracing

I'm trying to implement the multiple importance sampling path tracing, the MIS path tracing uses the MIS to combine the direct light sampling and brdf sampling to evaluate the direct lighting. The ...
yys_c's user avatar
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1 vote
1 answer
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Vulkan Ray Tracing analogue of Optix's OPTIX_BUILD_INPUT_TYPE_CURVES

Optix has OPTIX_BUILD_INPUT_TYPE_CURVES to model splines. The SDK comes with an example named optixHair. I could not find something like this under Vulkan RayTracing Extension, how could one implement ...
Vectorizer's user avatar
1 vote
0 answers
78 views

Perlin noise is mysteriously ignored when the pattern is rotated 45 degrees

I am creating different coloring patterns for my CPU raytracer, such as checker, gradient, ring, stripe pattern etc. The problems started when I tried to create a perturbation pattern (of a subpattern)...
Ave Milia's user avatar
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How can we represent a self-intersecting surface without analytic expression in computer?

Suppose we have a suface without self-intersection, then we can store it numerically using grid samples from its signed distance funtion. But what for the self-intersecting case, can we still use the ...
Andy's user avatar
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