Computer Graphics Stack Exchange
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How to do heterogeneous volume absorption using path tracing?

I want to do volume rendering using path tracing with a absorption only model. And my data is in a 3D grid, which is turned into a voxel medium in my renderer. However, I can't seem to be correct implementing the algorithm. According to this note…
jinglei
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Volumetric integration in Frostbite

In their presentation at SIGGRAPH 2015 Electronic Arts presented method of volumetric rendering using 3D texture aligned with view frustum. This technique needs two steps: Injection of color and density into 3D texture, Integration along Z axis of…
mdkdy
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Was Evans & Sutherland CT5 really created in 1981?

A few days ago I found a video on Twitter showing the Evans & Sutherland CT5 Flight Simulator system. It was labeled as 1981 footage and looked really amazing. The first time I saw similar 3D grahics in computer games was in the late 90s and in ealy…
Gonrah
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Compute sphere tangent for normal mapping

I'm implementing normal mapping on my toy pathtracer. I need to compute the tangent (and bitangent) of any sphere point in order to create the matrix that will transform tangent space to world space. More specifically, I want the tangent that runs…
MadEqua
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Tone Mapping & Gamma Correction

I've been looking up this question on the internet for a while, and I haven't been very successful, so I decided I'll ask it here. Should I apply tone mapping before gamma correction, gamma correction before tone mapping, or should I just use one or…
Daniel Kareh
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What happens to float values written to UNSIGNED_BYTE texture?

This is more a theoretical question. I'm wondering what happens when I write float values into an empty RGBA texture of type gl.UNSIGNED_BYTE in WebGL 1.0. Obviously, every channel then has 8 bits. But that wouldn't be enough to represent floating…
Muad
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Is placing z value of vertex in w enough to achieve perspective projection in OpenGL?

I have been learning about projection matrix in OpenGL and I am finding it really hard to understand. All I know is that there are other configurations in the projection matrix besides placing z in w for perspective projection. What are those other…
videogamechef
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Computation of conservative AABB for clipped triangle

I'm currently trying to implement a fast algorithm for KD-Tree construction using SAH, as described in this paper: On building fast KD-trees for ray tracing, and on doing that in O(N log N) I found one already working implementation by Miguel…
Michal Kučera
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Honouring Depth Test with Stencil Test

I'm using OpenGL's stencil test to carve out a semicircular hole in a transition frustum with a cylinder oriented perpendicularly. However as one can see below, while this objective is achieved, the cylinder is still visible through the frustum…
Sharat V Chandrasekhar
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What is the potential equation in PBR?

I'am studying PBR and the book introduce the potential equation. They said the potential equation can describe shooting algorithms better, and $W(x, \theta)$ describes the fraction of the radiance $L(x, \theta)$ But I could not understand the…
shashack
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row and column majored rotation matrix pre- or post- multiplied

For column-major rotation matrices (right up forward in columns) do you right-multiply (post-multiply?) a row vector or left-multiply (pre-multiply) a column vector to result in a correct/valid transformation? Or are both "valid" but just transform…
Matthew L
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The variance for the Monte Carlo estimator

I was wondering about the variance for Monte Carlo. The book (Advanced Global Illumination 2ed, p.60) writes the equation as follows: $\sigma^2 = \frac{1}{N} \int(\frac{f(x)}{p(x)} - I)^2p(x)dx$ $\space\space\space\space=\color{red}{\frac{1}{N}…
shashack
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Explanation of the Marching Squares saddle points resolution

I was reading the Wikipedia entry on Marching Squares, and was confused by the explanation of the saddle point disambiguation: Ambiguous Case: Basically, given the saddle points, the ambiguity is resolved by using the average data value for the…
user6750
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Rigorous and simple explanation for satisfying boundary conditions in Stam and Bridson papers

I read Stable Fluids and the code by Jos Stam and FLUID SIMULATION SIGGRAPH 2007 Course Notes by Robert Bridson. The boundary conditions in the two papers are different in my sight. I don't understand them. How are these two ways related to solving…
Anas Alaa
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Why is the back of a perspective frustrum larger than the front?

I'm following this tutorial on the perspective projection. Question: If the point of a perspective projection is to create the perspective effect (where objects faraway appear to be smaller): then why does it generate a frustrum in which the back…
George
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