# 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.

91 questions with no upvoted or accepted answers
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### 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 ...
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### 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: ...
238 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. ...
583 views

### What's the nature of Monte Carlo noise?

Monte Carlo rendering is just a process of sampling and reconstruction to evaluate the rendering equation. Why is it called noise rather than error?
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### Picking multiple light sources from a mixture densities

According to Peter Shirely paper, one pdf(probability density function) can be defined for the union of the light sources and pick only one using a random number from this density: p(x) = \alpha_1 ...
552 views

### Calculating intensities of Virtual Point Lights in Instant Radiosity from IES lights

Short introduction I created a function that interpolates the IES luminious intensities (candelas) using Hermite interpolation, so in my code all light sources have $I(\theta, \phi)$ function - but ...
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### 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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### Why my bsdf can not pass Chi2test?

I implemented a MicrofacetTransmission in nori. But it can not pass all Chi2test when alpha is large(>= 0.4 or ?),part of chi2test is passed.And I can not found the problem.Can someone help me? ...
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### Time Interval Ray Tracing performance

I found a very nice paper regarding Time Interval Ray Tracing for Motion Blur published in 2017. That was before RTX GPUs were on the market. I have a few questions about an optimal implementation and ...
51 views

### Shadow Bug when Raytracing Triangles

Spheres with shadows work fine. But when I try to include triangles with shadows, they are shaded incorrectly (i.e completely black): But when I disable shadows Blinn shading on triangles work fine (...
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### GL_OUT_OF_MEMORY Error when glDispatchCompute takes longer

I built a simple Ray Tracer which takes use of OpenGL's Compute Shader and traces ".obj" Files. The results are passed to the Host-Program via glMapBufferRange after finishing computing. ...
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### 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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### 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 (...
141 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 ...
151 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 ...
107 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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### 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. ...
112 views

### Tail Recursive Monte Carlo Raytracing

I am writing a raytracer in F# using montecarlo sampling I would like to make my recursive calls tail recursive but I am not sure of this is possible with MC raytracing as one has to evaluate sampled ...
146 views

### How to calculate solid angle subtended by a pixel?

How is the solid angle subtended by a pixel calculated? both in perspective and fish eye lens.