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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, ...
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1answer
67 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. ...
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0answers
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?
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1answer
95 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. $$f(x)=g(x_0\leftrightarrow x_1)W_{\text e}(x_1\to x_0)t_k(x_0,\ldots,x_k)L_{\text e}(x_k\to x_{k-1}),$$ ...
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0answers
27 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 ...
2
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0answers
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 ...
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1answer
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 ...
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3answers
162 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 ...
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1answer
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 ...
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1answer
41 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 ...
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0answers
80 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 ...
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0answers
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 ...
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0answers
51 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 ...
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0answers
27 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 ...
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0answers
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 ...
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1answer
85 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?
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1answer
59 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 ...
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0answers
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 ...
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0answers
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 ...
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0answers
52 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 ...
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0answers
48 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 ...
2
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1answer
91 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?
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0answers
71 views

Shader sampler2D uniforms instead of attributes

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 ...
1
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0answers
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 ...
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0answers
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 ...
1
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0answers
44 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 ...
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0answers
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 ...
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1answer
65 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 : ...
1
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1answer
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 ...
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1answer
117 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 ...
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0answers
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 ...
2
votes
1answer
44 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 ...
2
votes
1answer
35 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 ...
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2answers
59 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 ...
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0answers
97 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: <...
3
votes
2answers
108 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) ...
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0answers
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 ...
1
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2answers
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 ...
2
votes
1answer
135 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 ...
0
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0answers
24 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 ...
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0answers
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 ...
1
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2answers
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: ...
0
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0answers
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 ...
3
votes
1answer
48 views

Understanding distinct vs. not distinct knots in B-splines

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, \...
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0answers
41 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 ...
1
vote
0answers
73 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 ...
0
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0answers
41 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 ...
0
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1answer
69 views

Is there a term to refer to a cube-break-down process?

The image shown below illustrate the process to break a cube down into 4 small equal cubes. Is there a term to refer to this process, something like cube-break-down? Why would I like to know the ...
0
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1answer
64 views

Reading thesis on cone tracing, did the author make a mistake?

I am reading this document that talks about signed distance field rendering. In that document section 6.3, on the topic of cone tracing, it says: Cone tracing is an extension of the sphere tracing ...
1
vote
1answer
53 views

Point light illuminating only half of a scene

A point light is illuminating only a half of a scene in my small 3D renderer. It happens on every scene I've tried (conference room, cornell box, etc). How do I go about debugging this? What could ...

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