# All Questions

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### Procedural Generation of 4D Shapes

I'm curious if anyone has any insight into how one might procedurally generate 4D objects, as showcased in Miegakure (or the developer's other game, 4D Toys ). I built a program a while back to do ...
74 views

### Relation between camera sensor responsivity and image reconstruction filter associated with a pixel

Let $W_{\text e}$ denote the camera sensor responsivity (i.e. importance) and $h_j$ and $W_{\text e}^{(j)}$ denote the image reconstruction filter and sensor response associated with the $j$th pixel, ...
69 views

### Data structure of IFC-files

I know OBJ-files essentially are one or more lists of n-tuples containing information about the location of vertices, texture and normals. However, I am not sure how this is structured in an IFC-file. ...
22 views

### Convolution of multiple gaussian filters with different sizes

What is the size of the final filter after implement convolution of multiple gaussian filters with different sizes?
97 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. $$f(x)=g(x_0\leftrightarrow x_1)W_{\text e}(x_1\to x_0)t_k(x_0,\ldots,x_k)L_{\text e}(x_k\to x_{k-1}),$$ ...
34 views

### Sampling the depth component of a packed depth-stencil texture while rendering to its stencil component

I need to frequently perform depth testing for any given fragment at a different fragment location than the one rendered to. Since this isn't possible with normal builtin OpenGL depth testing ...
134 views

### Scaling of the final image in Metropolis Light Transport

I don't understand why the PBR implementation of Metorpolis Light Transport scales the final image by b / mutationsPerPixel. The authors write: Each Metropolis ...
48 views

### Determining shortest vector between a ray and an axis-aligned 3D bounding box (correcting a near-miss)

I have a situation where (due to floating point error) a ray that is known to hit a bounding box fails due to floating point error. (1e-8 or so) Expanding the box is not an acceptable solution in my ...
188 views

### perspective matrix derivation

Now there has already been an answer here in this stackexchange, but I don't understand certain aspects of it. The author has MORE DETAILED DESCRIPTION HERE(#1) but the problem is he doesn't describe ...
68 views

### Graphics engines during the sixth console generation

From my understanding game developers used mostly proprietary, in-house graphics engines during the sixth console generation (Xbox, PS2, GC, DC) on a game to game basis. Why didn't standard engines ...
47 views

### Extracting information from EXR Files

I am relatively new to computer vision and image processing. I have a single EXR file with 7 channels: 1-3 give me the RGB values, 4-6 give me the surface normals coded as RGB values and 7th channel ...
85 views

### how is zooming done in computer graphics

Since a projection plane and a center of projection is used for achieving perspective projection, the shape of the view frustum doesn't change changing the focal length(which is the distance from the ...
28 views

### Loop subdivision, certain areas converging towards degenerate geometry

I coded loop subdivision and ran it on a cube with triangle faces. I noticed this: I am using doubles to represent my vertex positions, I am not 100% sure these are caused by floating point ...
53 views

### What is it that really prevents photo-realistic, real-time, digital 3D simulations?

Ever since I was a small child, seeing the amazing 3D visuals that developed in the 1980s and 1990s, I was certain that photo-realism was "just around the corner". In the year 2020, I certainly ...
28 views

### Quantify the variance of pixel measurements

Say $E_j$ is an estimator of the value $$I_j=\int f_j\:{\rm d}\lambda$$ of the $j$th pixel given by the path space integral of the corresponding measurement contribution function $f_j$. $f_j$ is of ...
33 views

### Is casting a shadow ray non-symmetric in pbrt?

According to the description in the book, Scene::IntersectP() "checks for the existence of intersections along the [passed] ray". This operatorion should be ...
90 views

### Sending programs from CPU to GPU

How does a CPU know which piece of code should be executed on GPU (i.e how to recognize whether a code is shader or not) and how is it been sent to GPU VRAM?Is it via DMA?
63 views

### How to handle Half edge boundary edge iteration from vertex?

Ok so let's say we have a portion of a mesh that looks somewhat like this: A triangle fan with one of the triangles removed. If that triangles was not removed, we could get all the edges adjacent to ...
41 views

### Case where ray hits corner of box

I am writing a path tracer and when wrting method for returning the normal for the plane that was hit, I am not quite sure what to do when the ray hits box in a corner, placing the intersection point ...
46 views

### Formula for non area light BRDFs

I'm reading a graphics book and it talks about BRDFs being the ratio between differential outgoing radiance and differential irradiance. The formula it gives is f(l, v) = dL(v)/dE(l) Where l is the ...
55 views

### Understanding Oren-Nayar reflectance model

In the Oren–Nayar reflectance model, each facet is assumed to be Lambertian in reflectance. wiki My understanding : Law of reflection tells us that angle of incidence is equal to angle of ...
51 views

### Mesh boolean and amount of triangles

Inspired by BSP tree mesh operations, I've implemented an operation that takes a mesh X, a BSP tree/sequence of planes, and creates a new mesh, by iteratively slicing mesh X by these planes in some ...
93 views

### How do people come up with subdivision schemes?

Be it chaikin subdivision, loop subdivision, catmull-clark subdivision... How do people come up with the coefficients for an arbitrary subdivision scheme?
80 views

In the godot game engine (using opengl) it is not possible to define custom shader attributes. A workaround is creating a sampler2D texture uniform instead and use vertexId (or in fact UV since ...
37 views

### How do I fix skipping ray-triangle intersections on concave edges/cavities of model?

I'm writing a path tracer and I have a problem with ray-triangle intersection tests. The problem happens most frequently with materials that implement random scattering of the ray. Here's a function ...
33 views

### Problem with Quad-based Tessellation in GLSL generating incorrect vertex ordered tessellation

I am trying to perform quad-based tessellation using GLSL on Unity to be able to render polynomial-based parametric surfaces on a Unity quad. The quad-based tessellation using GLSL seems to be ...
46 views

### Implementing the derivation of the Smith Shadowing function for arbitrary distributions

I'm trying to implement the derivation of the masking function G_1 by Smith. The appendix of Walter et al 1, Hammons presentation 2 and this research paper 3 talk in detail about it and I feel as I do ...
16 views

### What are the options/limits for high definition live video streams?

Assume we have a small computer (for example the Tegra Xavier board from nvidia), which is connected to a second computer. On the small computer we have a new frame in raw format. We want to send ...
68 views

### basic of image dithering

Is just read about image-dithering ? So I tried to implement that. Here is my result. Can someone verify it? My code : ...
73 views

### Defining “inside” and “outside” of a 3D space

I am not sure if this is the correct SE to ask this question. However, lets say I have been given 3D models of several enclosed spaces. I want to populate spaces with, lets say, planes flying through ...
124 views

### Which technique should be used for rendering under water images, Ray tracing or Radiosity?

Rendering is the process of computing a three-dimensional geometric description of a scene into a two-dimensional image representation that looks real. Ray-tracing and Radiosity are two of the most ...
15 views

### Turning layered curves to polygon mesh?

I am confronted with the problem to render 3D representations for objects marked on microscope slices. So I have a set of aligned polygons in parallel planes from tracing the outline of the object in ...
45 views

### How to subdivide faces with a half edge DS?

Assume we have a mesh represented as a half edge datastructure. We want to subdivide faces without introducing unnecessary vertices (i.e the new number of vertices must be exactly V + E where V is the ...
37 views

### 2D array texture with different filtering setting per texture?

Currently I have textures which need GL_NEAREST and some other need GL_LINEAR in the same texture2dArray. In the shader I perform a manual GL_NEAREST lookup via textureFetch(). To avoid this my ...
61 views

### How does graphics api like OpenGL determine which triangle is back face to cull?

When I was writing a software rasterizer for my university class, we did culling in eye coordinates. Essentially, we use cross product to get a normal from the 3 vertices (in eye coordinates), then ...
103 views

### Unable to implement firebaseui auth in android app

i was trying to integrate firebase authentication in my android app using implementation 'com.firebaseui:firebase-ui-auth:4.3.1' but i am getting the errors: <...
110 views

### Need a fast ray-box intersection that handles if a ray is parallel and in line with a plane of the box

I've seen lots of spins on the ray-box intersection test, and a lot of them seem to boil down to this code: (omitting some details here) ...
22 views

### Algorithm to reproject texture after wrapping mesh using ICP?

I was watching this video, where given a base mesh we wrap it in a scanned mesh, I can imagine how to implement something similar from scratch, but I was wondering how can I assign uv coordinates to ...
43 views

### Blackbody curve to floating RGB

I want to set the color of the lamps in my game with a black body curve, but the approximations I can find for it are all in sRGB color space; and I want it in linear floating RGB. The closest thing ...
147 views

### Sampling the light vs. sampling the BRDF: difference in intensity

(possible duplicate) I'm trying to implement multiple importance sampling, as described in the PBRT book (no bouncing yet, I want to make MIS work first). What my problem is, that while the BRDF ...
26 views

### void* D3D11_MAPPED_SUBRESOURCE::pData to OLE_COLOR* possible?

I have found the following from this link enter link description here pData Type: void* Pointer to the data. When ID3D11DeviceContext::Map provides the pointer, the runtime ensures that ...
16 views

### Explanation request for a GDI code block

I have a small old code snippet where I am not sure what is actually someone wanted to do. As I am not doing and trial and error guessing dvelopment. I have to be certain about the purpose could do ...
45 views

### Y axis inversion in 3D rasterization

What is the correct way to invert the y axis during the 3D projection? I see a lot a people doing: ...
41 views

### Find the inside and outside relationship of connected components in a mesh

I extract a mesh from a method similar to Marching cubes. I want to estimate the topological relationship between connected components. For example, below, let's assume that we have 4 connected ...
49 views

In reading the wikipedia page about B-Splines https://en.wikipedia.org/wiki/B-spline, I am getting confused about the concept of knots. If we have a spline of order $n$, with a knot vector ($t_0, \... 0answers 44 views ### Non linear transformation of vector graphic I want to do a non-linear transformation of a svg in python. My specific problem is to transform a rectangular svg image into a frustum like image, for which i have a mathematical equation of the form ... 0answers 90 views ### Why does Schlick's approximation contain a \$(1-\cos\theta)^5\\$ term?

The approximation writes the reflection coefficient as$$R(\theta)=R_0+(1-R_0)(1-\cos\theta)^5,\,R_0=\left(\frac{n_1-n_2}{n_1+n_2}\right)^2.$$Why is the exponent 5? Schlick 1994 introduces this ...
42 views

### Rotation around local axis

I am trying to understand rotation and I come across the scenario of rotation with respect to the object itself. One strategy that makes sense to me is that I would translate and rotate one of the ...