# 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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### 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 ...
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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' ...
684 views

### Problem with definition of BSDF and radiance

When I was reading theory behind physical based rendering I noticed that definition of BSDF and radiance has some problems. For example BSDF of purely specular surfaces is zero almost everywhere and ...
116 views

### 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 ...
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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 ...
244 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. $$f(x)=g(x_0\leftrightarrow x_1)W_{\text e}(x_1\to x_0)t_k(x_0,\ldots,x_k)L_{\text e}(x_k\to x_{k-1}),$$ ...
353 views

### mapping of a point from a sphere into UV plane

I am reading the book An introduction to raytracing by Eric Haines and it mentions an algorithm to map a point from a sphere into a UV plane, it calls it Inverse Spherical Mapping (page 49). I googled ...
1 vote
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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 ...
294 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 ...
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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 ...
1 vote
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### 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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### 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 ...
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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 ...
1 vote
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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 $f$ ...
1 vote
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### 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 ...
98 views

### 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 ...
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### Is the scene being drawn correctly with my raytracer?

I have a ray tracer that I wrote myself. I am not sure that the scene is being drawn correctly, to be more precise, are my reflections on the floor and on the sphere correct? My scene: ...
127 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 ...
2k views

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 ...
1 vote
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### 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 ...
329 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, ...
1 vote
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### 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 ...
1 vote
98 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 ...
1 vote
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### 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. ...
104 views

### PBRT: why normalize ray's direction

In PBRT Chapter Camera Model, when describing Camera::GenerateRay(), it writes It is important that the direction component of the returned ray be normalized—many ...
1 vote
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### 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: ...
81 views

### 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 ...
1 vote
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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 ...
1 vote
59 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 ...