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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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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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60 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
92 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
82 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
85 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 ...
3
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1answer
67 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
72 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
81 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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101 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
92 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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2answers
102 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
76 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
119 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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1answer
182 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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2answers
89 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. ...
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1answer
80 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 (...
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3answers
216 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
100 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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1answer
198 views

OpenCL ray tracer: which is better, geometry code on device side or on host side?

I am writing a ray tracer using openCL, and following this tutorial http://raytracey.blogspot.com/2016/11/opencl-path-tracing-tutorial-2-path.html However, I find that the author has two copies of the ...
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1answer
151 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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2answers
180 views

Radiance at a nearly perpendicular angle is almost infinite?

As far as I understand, radiance is a measure of the "intensity" of light in a direction defined as a differential cone . It's measure is Flux per solid angle per projected area. $L = \frac{d\Phi}{d\...
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1answer
140 views

Where should the ray origin be put in perspective camera ray tracing?

Where should the ray origin be put in perspective camera ray tracing? The following gives a picture of the ray tracing in the perspective camera setting: http://www.cs.cornell.edu/courses/cs4620/...
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1answer
101 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
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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/...
5
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1answer
159 views

High variance in path tracing specular objects

I'm testing my path tracer for specular surfaces. Images rendered with my own code have very noisy appearance, and I think they look like variance. I use point light and the bunny is of mirror ...
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0answers
22 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 ...
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1answer
142 views

Defocus blur: Computing the pixel plane distance

I'm following Peter Shirley book, Ray tracing in one weekend. In the last chapter, he talks about how to make defocus blur by using thin len approximation. His camera class accepts a parameter called ...
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158 views

ray-triangle intersection precision - c++

I'm building a software renderer but I think there might be some problem with my ray-triangle intersection accuracy. I implemented the algorithm referring to ...
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1answer
101 views

How does Primary Sample Space Metropolis Light Transport work?

For simplicity, assume we're only dealing with surfaces which have either a Lambertian or perfectly specular material. Morever, assume that the only type of lights are area lights (i.e. surfaces with ...
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1answer
3k views

Raytracing: why are the spheres in the image below appear stretched?

Some context. Above are the code and the resulting image for it in Peter Shirley's Raytracing in one weekend's book. As you can see from the code, he adds in some spheres. And yet in the final image ...
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0answers
151 views

Ray tracing implicit surfaces using Sturm's theorem

I am trying to render implicit surfaces given by a polynomial equation $F(x,y,z) = 0$ using Sturm's theorem. Plugging the parametric ray equation $r(t) = o + td$, where $o\in\mathbb{R}^3$ is the ray ...
3
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1answer
102 views

why doesn't a ray hitting a sphere at only 1 point count as a hit in sphere/ray intersection?

To give context to the question, I am reading Peter Shirley's Ray Tracing in one weekend. In his code for sphere/ray intersection, when the quadratic formula returns only 1 solution, he discards it, ...
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0answers
52 views

fastest way to bucket triangles into a grid?

What is the fastest known method for bucketing triangles into an unbounded regular 3D grid? Specifically, I need an array of buckets. Random queries (which bucket is here) are not necessary, as this ...
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1answer
64 views

How to raytrace triangular faces when camera is not at origin?

I've watched the Pixar In A Box, Maths of Rendering Tutorial on Khan Academy. I've started writing a raytracing program and have come to the point where I must solve for ...
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0answers
71 views

Compute emitted importance of a pinhole camera

In section 16.1.1 of Physically Based Rendering the authors describe how we can check, if a given ray $r$ corresponds to one starting from the film area. They implement this check such that it works ...
2
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1answer
71 views

How do we approximate the integral of the measurement contribution function in Metropolis Light Transport?

In Metropolis Light Transport, we need to approximate the integral of the measurement contribution function. I've read that this can be done using a traditional approach like path tracing. However, ...
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1answer
109 views

How can we convert a probability density according to solid angle to a density according to area?

In Chapter 14.5.3 of Physically Based Rendering - From Theory to Implementation (3rd edition), the authors claim that a probability density $p_\omega$ according to solid angle can be converted to a ...
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1answer
159 views

Using multiply and accumulate of 4x4 matrices for ray-triangle intersection tests on GPU

Is it possible to gain performance boost using new 4x4 MAD from NVIDIA'a tensor cores for ray-triangle intersection tests? Really there are two questions: Is it possible to modify some of the ray-...
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1answer
168 views

Light field rendering for 3d software?

Is there any 3d software that supports rendering an artificial scene to a light field image? With that I mean an image capturing light from more than one point in a scene, more lika a spherical ...
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1answer
318 views

Ocean Wave Rendering

How could I generate the waves for a water body with whitecaps & foam and variable intensity of the waves? Is the surface a mesh with a normal map? Is there a formula for generating that? Is there ...
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1answer
202 views

Problem of understanding the coordinate systems involved in ray tracing

This picture depicts my current immagination of the coordinate systems involved in ray tracing: Explanation: So the green rectangle is the [-0.5, nx-0.5] x [-0.5, ny-0.5] coordinate system and you ...
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1answer
172 views

Is there ongoing research on Markov Chain Monte Carlo algorithms (other than Metropolis-Hastings) for use in ray tracing?

Metropolis Light Transport is an application of the Metropolis-Hastings algorithm. Its variants differ only in the used "mutation strategy". Is there ongoing research on other Markov Chain Monte ...
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1answer
141 views

Bright artifacts in ray tracer rendering seemingly caused by reflections

I've been working on a new ray tracer recently, but after adding reflections I'm seeing these strange small highlights on my models, particularly on the ear of the silver rabbit below. I've read ...
2
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1answer
388 views

How does a path tracer with next-event estimation work?

I am trying to implement a simple path tracer with next-event estimation in Java. The general idea is to trace a ray through the scene as usual (using a cosine distribution to determine the next ...
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1answer
277 views

Should direct illumination and path tracers render the same scene equally bright?

I am using the book Ray Tracing from the Ground Up by Kevin Suffern to build my first ray tracers in Java. Based on the theory, I expected that direct illumination and simple path tracers render the ...
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1answer
178 views

how to render colored glass object?

I want to know how to deal with the color of object,Should i use diffuse reflection on the surface?
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0answers
158 views

How exactly do soft shadows get generated using a voxel cone tracing rendering technique?

Let's assume we have voxelized a scene, and all of our materials have an opacity level of 1. The reuslt would then look like: If we raytraced the final volume that gets generated after rasterization. ...
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1answer
161 views

Self intersection artifacts in 3D image raytracing

I am developping a voxel raytracer for global illumination. I have been successful in multiple aspects but there is a problem I am not sure how to solve. The model works as most other Voxelization ...
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1answer
2k views

Difference between BVH and Octree/K-d trees

So I'm currently reading up on acceleration data structures and so far I've heard there are 2 main schemes. Object Subdivision and Spatial Subdivision. The Bounding Volume Hierarchy belongs to the ...
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How to ensure that the raytrcing coordinate system is teh same as the projection one?

I have 2 shading models right now, one is using voxels the other one is the standard projection absed renderization method. Putting them side by side I have noticed that no matter what I do one is ...