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Lots of bad samples (below hemisphere) with the GGX VNDF

I've noticed that my implementation of GGX VNDF sampling produces quite a lot of bad samples (below the hemisphere). When such a sample occurs, I terminate the ray, leading to an immediate black pixel....
Tom Clabault's user avatar
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0 answers
8 views

HealPix: Different results when comparing C++ and Vulkan

I have converted the algorithm for calculating the HealPix value from Lat/Lon values from C++ to GLSL. The result is saved in a BMP image and looks correct. Both algorithms (C++ and GLSL) use the same ...
Thomas's user avatar
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1 vote
0 answers
32 views

Darkening in ReSTIR DI spatial reuse implementation

I'm currently implementing the spatial reuse pass of ReSTIR DI in my path tracer but I'm having some form of darkening/bias at the edges of objects (visible on the tall box + lightening visible on the ...
Tom Clabault's user avatar
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0 answers
13 views

Measuring sphere angles to triangle

I'm looking at using multiple importance sampling for path tracing, and doing some lighting calculations relating to spherical lights. I'm trying to decide, given a triangle and a point on that ...
Puppy's user avatar
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1 answer
9 views

Vulkan+glm orthographic projection clipping unexpectedly

I am following along https://vulkan-tutorial.com/ and just finished the chapter on Uniform Buffers. I tried to change the projection matrix to see the outcome, however, when I change the zFar value in ...
Vulkan_Learner's user avatar
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13 views

In Vulkan - OpenGL interop, what tiling would an image need?

I have set up a program that does Vulkan - OpenGL interop. I heavily borrowed from the Vulkan Sample. The idea is: Vulkan creates an image and semaphores. OpenGL will render to the image and Vulkan ...
Tare's user avatar
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1 answer
17 views

Set usage efficiensy and problems in VUlkan

I am learning Vulkan, and through the process of developing a renderer by Vulkan guide(extra-engine sample), I got questioned whether I should use different sets for uniform buffers (camera data/...
Ciborg's user avatar
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0 votes
1 answer
31 views

Microfacet-Based BRDFs general form

In Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs, author said that "we differentiate Equation (17)" but how to get 2 from 1?
Chen's user avatar
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1 answer
25 views

How do the vulkan fences behave on the GPU?

I went through a lot of Vulkan tutorials and each of them has talked about fences, which is good, but each of them does not clearly tell what exectly happen on GPU. It is so frustrating trying to ...
Thomas's user avatar
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27 views

Jump Flood Signed Distance Field Computation Is Incorrect

I am trying to implement the Jump Flood Algorithm (JFA) to compute the Signed Distance Field (SDF) of a glyph atlas for font rendering. I managed to set up my framework (OpenglGL-based) for running ...
Chaos's user avatar
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0 answers
15 views

SImple Harmonic Motion blur removal

I have an image with lots of point sources and there looks like a motion blur in one axis, with point sources being transformed into hourglass shape. I presume this is due to a vibration in the image ...
James's user avatar
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29 views

How do computer screens display an image with a different resolution than the display?

This is obviously a contrived toy example, but... How would a 20x20 image be displayed on a 30x30 screen? Some pixels must be interpolated, yes? Is there a standard procedure for this or is it ...
Ben's user avatar
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0 answers
17 views

pdf derivation of distance sampling in volume path tracing?

According to this note of volume path tracing, Page 5, I'm confused of the derivation of p(s) in the first red box of the image and the equation in the second. How to derive? Any reference?
cedar's user avatar
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0 votes
1 answer
30 views

What is the intended behaviour when transforming normals with view matrix

I am writing a basic rasterizer and I'm testing to see if my normals are set up and handled properly by shading a sphere with its vertex normals to obtain For context, we are looking in the +Z ...
Scene's user avatar
  • 157
0 votes
2 answers
43 views

Overweighting certain lights with ray tracing

I'm just getting started with ray tracing with DXR and I'm building some simple lighting with it. I've run into a slight issue; namely, that my game is set in space. Therefore the vast majority of all ...
Puppy's user avatar
  • 103
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0 answers
5 views

Unable to define/use my own macro on HLSL Unity3D

I defined a macro like: #define UNITY_SAMPLE_TEX2DARRAY_GRAD(tex, coord, dx, dy) tex.SampleGrad(sampler##tex, coord, dx, dy) to be used on this code: ...
z3nth10n's user avatar
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0 votes
0 answers
14 views

Vulkan vkCmdCopyBuffer with Semaphores

I am trying to copy data from one buffer to another. I have two VkSemaphores (each buffer has one) that should be checked before the copying process starts. And which should be signaled when the copy ...
Thomas's user avatar
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0 votes
1 answer
25 views

Vulkan synchronization stageBuffer

I am writing a program that uses a transfer queue and a compute queue. As the names suggest, the transfer queue loads data from the CPU to the GPU and from the GPU to the CPU and the compute queue ...
Thomas's user avatar
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1 vote
1 answer
48 views

PRBT - Transforming between Distributions (Section 2.4)

In the 4th edition of "Physically Based Rendering" here: pbrt book 4th ed Section 2.4 in Section 2.4 "Transforming between Distributions", it is said "Suppose we are given a ...
Simon's user avatar
  • 193
1 vote
0 answers
57 views

How is this transmittance derived?

In PBRT 4ed https://www.pbr-book.org/4ed/Volume_Scattering/Transmittance#eq:volume-attenuation-differential How is this transmittance equation transformed from 11.9 to 11.10? \begin{equation} \int_0^d ...
Sopiro's user avatar
  • 11
0 votes
0 answers
39 views

Ocean screen grid projection and animation

I am trying to port the Bruneton Ocean demo to Vulkan and I am having a bit of trouble with the coordinate system. I am using the matrices from the original code but I am not sure what this is doing: <...
Marco Castorina's user avatar
0 votes
0 answers
26 views

Why am I getting darker results in RGB grid volume rendering?

I am rendering an RGB volume. The volume is 4D: (X, Y, Z, D), with D = 3 (RGB values). Previously I am able to render the mono-chromatic volume, using exact the same idea presented in pbr-book: ...
Enigmatisms's user avatar
  • 1,087
0 votes
0 answers
31 views

Name of non-standard perspective projection where parallel lines do not meet at a single vanishing point

I have made a non-standard perspective projection for a rectangular room (see left figure), in which for stylistic reasons, I chose to make the perspective "width" of the walls equal ...
eziama's user avatar
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3 votes
1 answer
109 views

How to have caustics at all in a path tracer with next event estimation?

When doing next event estimation, you trace a shadow ray to a light source to test visibility. What if there's a glass/transmissive object in the way? The light will be occluded and we won't get any ...
Tom Clabault's user avatar
0 votes
0 answers
29 views

Change the shape of the caret in ImGui

I would like to change the shape of the caret in ImGui, either to a wider one or to an underscore. I'm not sure where to start. I would also like to change the blinking rate if possible. Thanks for ...
Bartolini's user avatar
1 vote
1 answer
44 views

Multiple Importance Sampling BSDF + Light - weights confusion with the number of emissive triangles

I'm trying to implement multiple importance sampling for direct lighting estimation but I'm having a hard time understanding why adding the number of triangles to the PDF of my light sample yields ...
Tom Clabault's user avatar
0 votes
1 answer
24 views

Clarification on PPI

I wanted to convert a chart rendered by canvas element to an image file so that the user can download it. But the official HTML docs say that: The created image data will have a resolution of 96dpi ...
Urooj's user avatar
  • 111
1 vote
1 answer
40 views

Blinn-Phong specular light bleeding on triangles facing-away from light: what is the canonical solution?

In our implementation of the empirical Blinn-Phong shading model, we are facing a problem with light-bleeding of the specular component. The model defines the half-vector $\vec{h} = \frac{\vec{v} + \...
Ad N's user avatar
  • 111
2 votes
1 answer
64 views

How is Shader Execution Reordering implemented under the hood?

I am writing a software path tracer from scratch in CUDA (for learning purposes, without resorting to any higher-level graphics API like OptiX), and it is well-known that path tracing can have ...
Enigmatisms's user avatar
  • 1,087
0 votes
2 answers
75 views

How are surface normals dealt with in the graphics pipeline?

I know the process for regular vertices is something like: model coordinates to clip space via the "MVP" matrix transformation, then perspective division, screen-space mapping, and finally ...
Scene's user avatar
  • 157
1 vote
0 answers
34 views

How to get the shortest segment AB between 2 SDF (Signed distance field) in 3D?

Is there a method to find the shortest segment between 2 Signed distance field? I know how to calculate this segment for a limited number of SDF like from sphere to sphere, from capsule to sphere, ...
Kuwazy's user avatar
  • 11
2 votes
1 answer
42 views

Would there be a point in creating monitors that have more than the regular RGB color channels?

I was thinking about color spaces and the coverage between the sRGB and Lab color spaces such as OkLab. I was wondering if there could exist some different monitor technology with more than 3 color ...
FatBaz's user avatar
  • 21
0 votes
1 answer
36 views

How are these two projection matrices related?

I have two 3D perspective projection matrices $A,B$ with standard projection parameters $k=\cot(\theta/2)$, where $\theta$ is the field of view, $n$ is the $z$-near value, $f$ is the $z$-far value, ...
Scene's user avatar
  • 157
3 votes
1 answer
48 views

What to do with the homogeneous $w$ during vector operations

As I understand it: In graphics, 3D vectors are usually represented as homogeneous coordinates by storing an additional $w$ component known as the weight. The vector is divided by $w$ to obtain the ...
Scene's user avatar
  • 157
0 votes
1 answer
61 views

what technicalities involved in screenshot process? what is the dependency of screen properties in the screenshot of an image?

If we take screenshot of image displayed on a monitor screen, then does it take only framebuffer data? Does the framebuffer data is independent of display screen properties like contrast, brightness? ...
Techie's user avatar
  • 1
2 votes
1 answer
43 views

Possible reason for buffer orphaning being faster than using glBufferSubdata even when changing the size of that data?

I recently conducted an experiment, where a large scene was split into two types of mesh data - static (the terrain) and dynamic (lots of low poly trees). I evaluated two memory layouts and update ...
rbaleksandar's user avatar
0 votes
0 answers
9 views

DrawArrayInstanced is not rendering what it should (OPENGL)

...
EnVadeh's user avatar
0 votes
0 answers
10 views

Issues with vxgi implementation when rotating the camera

right now I have implemented vxgi algorithm. Voxelization is working fine, same for mipmap generation. But, I have an issue when I rotate the camera. Basically, it is not stable when it is rotated. I ...
Zhukov Artem's user avatar
0 votes
1 answer
30 views

How to achieve smooth max of two coordinates in a shader

I am trying to achieve a border effect to a square tile on a xz plane. I am using max of coordinates x and z to achieve that. Here is my ShaderLab code: ...
hungry91's user avatar
1 vote
1 answer
52 views

Is the light emitted by a typical white pixel actually a blue-ish purple to compensate for our greater sensitivity to the color green?

The human eye is considerably more sensitive to green light than red or blue; this is expressed in formulae which calculate an approximate overall "luminance" value for a RGB color (example)....
jameswilddev's user avatar
0 votes
1 answer
47 views

Pose representation using rigid transformations

In literature (3D graphics, computer vision, 3d deep learning etc.) I notice that often an object's pose is represented using a rigid transformation, i.e a member of the group SE(3) combining a ...
giorgio's user avatar
  • 133
0 votes
1 answer
92 views

How does ray tracing handle the calculation of reflections and shadows in the presence of multiple translucent objects?

Raytracing can handle the interaction between light and multiple translucent objects in a scene by using global illumination and raytracing with volumetric effects to calculate the color of the object ...
Arunabh's user avatar
  • 103
0 votes
0 answers
26 views

Is it possible to use OpenGL ES extensions in OpenGL? If not, why?

I've been looking at KHR_texture_compression_astc_hdr for OpenGL. It seems it's only currently supported by OpenGL ES 3.2. My GPU is an Nvidia RTX A3000, which does ...
Cascades's user avatar
  • 113
1 vote
1 answer
72 views

Is there a quicker way to draw a symmetric, scale-invariant (declining color) gradient around an ellipse?

The goal is to generate a picture like this: A symmetric color gradient around an ellipse which is rotated by $\theta$, has $(x_\circ,y_\circ)$ as center and and major and an minor axis $a,b$. The ...
UncleBob's user avatar
1 vote
1 answer
46 views

In perspective projection matrices, why isn't $z_\text{eye}$ mapped linearly to NDC?

As far as my understanding goes, in projection matrices $x_\text{eye}$ and $y_\text{eye}$ are mapped linearly to NDC by first using proportions to find $x_n = \frac{n\cdot x_e}{-z_e}$ and $y_n = \frac{...
blvck_mvgic_dot_exe's user avatar
0 votes
0 answers
34 views

Unit tests and code coverage tool for GLSL compute shaders

I use some compute shaders for some GPGPU usage. Each method of each shader must have unit tests. These unit tests must cover more than 95% of the code. I am looking for tools that I can use to write ...
Thomas's user avatar
  • 1,299
0 votes
0 answers
12 views

Tools to identify the cyclomatic complexity of GLSL code

In principle, cyclomatic complexity is a quantitative measure of the number of linearly independent paths through the source code of a program. I am forced to keep the cyclomatic complexity of our ...
Thomas's user avatar
  • 1,299
2 votes
0 answers
31 views

Algorithm to extract key points from line drawing

I have orthographic 3-view black and white line drawings like this: I would like to extract a set of 'key points' from this kind of drawing. By 'key point', I mean corners and a few points along ...
Rob McDonald's user avatar
1 vote
0 answers
46 views

Projecting a texture onto UVs with GLSL

I am trying to project an image overlayed on top of a mesh in screen space back to it's uvs. The UV triangles do not always cover entire pixels so i get this. The red is showing where the texture is ...
Dusan Bosnjak 'pailhead''s user avatar
1 vote
1 answer
44 views

Distance sampling with unbiased transmittance estimators

I'm currently trying some things with transmittance estimators in PBRT and I have implemented the following paper: Unbiased Ray-Marching Transmittance Estimator. This method assumes that two points $x$...
Matthias K.'s user avatar

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