# Tag Info

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From the ray tracing wikipedia page https://en.wikipedia.org/wiki/Ray_tracing_(graphics): "Path tracing is a form of ray tracing that can produce soft shadows, depth of field, motion blur, caustics, ambient occlusion, and indirect lighting." So a path tracer is a ray tracer, but not all ray tracers are path tracers.

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Your definition for radiant intensity is wrong: it should be just $\Phi / 4\pi$. There are only $4\pi$ steradians in a sphere no matter how big it is, so $r$ doesn't come into it. Also note that you can't calculate radiance for a point source—it would be infinite, due to the fact the point source emits a finite amount of flux compressed into zero size. It ...

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Yes, throughput doesn't have to be in range [0, 1]. That's a reason why you have to use exposure settings, because for differente accumulation time, brightness of an image might differ. Nathan Reed described it in details here - https://computergraphics.stackexchange.com/a/10244/10129 Your final results and number of fireflies and bright surfaces, depends on ...

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I know this is a pretty old question, but I am wondering if the problem does not come from sampling the whole hemisphere of the light, instead of only the visible portion of it from the hit location's point of view (see this : schuttejoe.github.io/post/arealightsampling) ? The visible solid angle is only 2*PI*(1 - cos(theta)) instead of 2*PI.

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This is an answer to your comment rather than the title of your question. It can be considered as a partial answer. The bias in path tracers are introduced by the estimators. For example, think of the following two equations: $$I = \int_{\Omega} f(\omega) d\omega$$ $$F = \frac{1}{N} \sum_{i}^{N} \frac{f(\omega)}{p(\omega)}$$ where $p: \Omega \to R$. It ...

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This would be a response to why is it possible to use the Fresnel equations in an RGB path tracer. Though evaluating Fresnel equation directly requires some what more information about the environment in which the rendering takes place, it certainly is possible to use it in an RGB path tracer. Here is why: TLDR: see last two paragraphs. The goal of Fresnel ...

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Observe that you can construct another graph by connecting the centroids of faces with centroids of adjacent faces. This is known as the dual. The edges of the graph between the centroids can be represented as the twin relation between halfedges. Then you can use something like Depth First Search to visit all the faces: function visit(f) mark f as visited ...

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This question is the result of the modern era using the blanket word ray-tracing to denote every similar technique as it's based off of it. Just wanted to give a more historical answer if anybody is interested. As lightxbulb said, historically, Turner Whitted was the first person to come up with the raytracing technique but it only had a limited number of ...

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If it’s on the wrong side of the normal, you don’t have to throw it away—negating it will give you a vector that’s in the visible hemisphere. Answering your comment, to get a vector that’s within some angle θ of the normal, this should work (GLSL): vec3 direction(vec3 normal, vec2 randomValues, float maxTheta) { // pick an orthogonal tangent vector using ...

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Shadow rays that hit a glass surface or similar are stopped because there's no direct path from the light source to the shading point—there's a piece of glass in the way. for perfectly specular transmission/reflection, you can continue tracing the shadow ray because there's only one possible outgoing vector for a given incoming vector That won't work, ...

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It sounds like you yet have to adjust the importance function of the Markov Chain according to the way you assign paths to each of the two estimators, path tracing and ERPT. If you think about it in the framework of MIS, you have two estimators with binary weights (according to your threshold). Now, the simplest (but inefficient) option to combine them would ...

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Someone else feel free to correct me as I am not 100% certain, but from what I can gather: They are describing all the normalized vectors v, which point at the ray between points v1 and v2. They are doing this using one parameter angle φ. They are essentially interpolating between two vectors o1 and o2, with the equation v = o1 cosφ + o2 sinφ o1 is simply ...

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I managed to fix it. It was indeed related to repeating random sequences. The problem was the following. curandState* randState is an array of curandStates, and most calls to curand_* require a pointer of a curandState. I was sending the randState, the array, to curand_* functions and not for example, a pointer of one of its members. Now most of my images ...

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For sampling a uniform volume you use the mean free path of a photon: float dt = -logf(1.0f - Xi) / uT; where: Xi is a random variable in [0, 1] uT is the extinction coefficient (sum of out-scattering and absorption) The pdf of a raytime (t) in this uniform volume is given by: float pdf = uT * expf(-t * uT); In your case, you do not have a uniform volume, ...

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