All Questions
3,963
questions
1
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0
answers
62
views
Motivation for densities wrt the same measure in MIS
In Veach's thesis the MIS weights (e.g. using the balance heuristic) for two strategies with densities $p_1, p_2$ are given as $w_1(x) = \frac{p_1(x)}{p_1(x)+p_2(x)}$ and $w_2(x) = \frac{p_2(x)}{p_1(x)...
- 2,083
0
votes
0
answers
61
views
How many rays can one RT core calculate simultaneously?
I have noticed that all GeForce RTX cards, without exception, have an equal number of RT cores as they have streaming multiprocessors (SM). From this fact I assume that each RT core is associated with ...
- 101
0
votes
1
answer
31
views
Theoretical speedup from sample number in path tracing algorithm
Suppose, in a Kajiya style path tracing algorithm, I have 100x100 pixels, and I am using 32 samples per pixel. So, the total ...
- 125
0
votes
0
answers
33
views
Bright results when importance sampling GGX NDF
I've been trying to importance sample the GGX NDF of my Cook-Torrance BRDF for some time now but I can't get it right.
I've been following this article.
Here's my code for the importance sampling part....
- 135
0
votes
0
answers
89
views
Normalized Device Coordinates: Why normalize the Z value?
I understand that the normalized device coordinates are the result of the perspective divide of clip space coordinates and allow for an easy mapping of the xy coordinates to a physical screen. What I ...
- 164
1
vote
1
answer
96
views
Matrix form of an open uniform cubic b-spline
I'm trying to find the matrix form for the equation of a cubic b-spline. More specifically, the "middle" part, S_i(t), is pretty straightforward and available everywhere:
...
- 11
0
votes
0
answers
77
views
How to setup a 3D camera
I'm trying to figure out how to setup a 3D camera in WebGL. This is my first swing at 3D so a lot of the matrix stuff is new to me.
Code
The code can be reviewed in this CodePen: https://codepen.io/...
- 127
1
vote
1
answer
74
views
Importance sampling microfacet BRDF and coordinate frame
I'm trying to importance sample the Cook Torrance BRDF for my path tracer but I'm not sure about the part where you have to change the sample from one coordinate frame to another.
This resource states ...
- 135
0
votes
1
answer
67
views
How to scale down noise frequency?
I'm making a space game and so far what I have is a system to generate spheres with noise on them, making them planets. I make a sphere, create noise data, write that data to an image file, and then ...
- 11
1
vote
1
answer
100
views
How to get the accurate number of triangles of an wavefront obj model?
I am confused by a 'wavefront obj' file's true triangle number. For example, I downloaded the Rungholt scene from McGuire's Computer Graphics Archive.
...
- 125
3
votes
1
answer
121
views
How does the Communication between Monitor and GPU work?
I know that this Topic is highly Hardware dependent, so i am asking for the case that a monitor is connected to a GPU or motherboard via. Displayport/HDMI
I would like to know is how the monitor is ...
- 33
0
votes
0
answers
59
views
How to design an ergonomic software rendering pipeline with painter's algorithm?
I wrote my software renderer with C++20 and the DirectX Math library.
The pipeline so far consists of these steps:
I use vertex buffers (...
- 1
1
vote
1
answer
36
views
Curved world effect shader for heterogeneous mesh faces
I have a voxel based game, similar to Minecraft and want to apply the "curved world effect" like described here.
As I was using a per 1x1 face quad renderer, applying the effect went well, ...
- 113
0
votes
2
answers
172
views
Relative coordinates -- cumulative sum
I have a vertex shader happily producing all the vertices I want for a 2D plot. Now I want to also render a plot of the same data, but each point relative to the previous one, like SVG Paths using <...
- 11
1
vote
1
answer
45
views
What algorithm approximates a "hand sketched" look for rendering diagrams?
I see a number of applications where polygons, lines, splines, etc., are algorithmically given a "hand drawn" look. What algorithm or general approach is applicable for this?
As an example, ...
- 111
0
votes
1
answer
76
views
What is in a GPU driver?
There are 3 kinds of code that are contained in a GPU-utilizing program:
CPU code.
CPU-to-GPU or GPU-to-CPU bridge code. This is what DirectX actually is.
GPU code. In NVidia speak, this is called a &...
0
votes
1
answer
53
views
What are applications of 3D geometry to 2D geometry projection and occlusion handling?
As a layperson in the field of computer graphics, I rarely see practical applications of algorithms that take 3D geometry as the input (along with some camera and lighting parameters) and output the ...
- 103
1
vote
1
answer
45
views
Are systems like double pendulum used for generating terrain?
Looking at the output of the angle of this double pendulum made me think this was a good candidate for generating realistic looking terrain profiles. I can't be the first to notice this so I was ...
- 83
1
vote
0
answers
91
views
Does WebGPU Have Significant Feature/Functionality Gaps As Compared to Vulkan/DirectX12/Metal?
A friend and I are considering using webgpu native (more specifically C++ bindings) for a project. We were wondering, since WebGPU likely runs on top of Vulkan XOR DirectX12 XOR Metal at any given ...
1
vote
2
answers
522
views
fast algorithm to check if a point is inside/outside mesh
Usually a ray casting algorithm is used to determine whether a point is indide or outside a mesh. But this algorithm is slow.
Is there any fast algorithm to do this check?
My input mesh is a ...
- 31
0
votes
1
answer
74
views
How to pick values of ambient, diffuse, specular for Phong Lighting?
I have the following code in python using the vedo package
...
- 101
1
vote
0
answers
47
views
BlinnPhong sphere edges look worse than Phong. Am I doing it wrong? (code and pictures included)
First of all, I am completely new to this so please excuse me if this is a dumb question.
I am following the book Real-Time 3D Rendering with DirectX and HLSL, for now implementing shaders in Nvidia ...
- 11
0
votes
0
answers
28
views
View system transformation by Ian Ashdown
I am reading this book about to code your own radiosity renderer by Ian Ashdown Book link
There is a chapter about view-camera transformation, particularly the normalization process when he transform ...
- 151
0
votes
1
answer
42
views
My projection matrix for OpenGL fails on non-symmetric boundaries
Assuming my viewing volume has x coordinates varies from l to r, and y varies from top to bottom, and finally z-axis varies n to f, I derived the following projection matrix:
...
- 3
0
votes
0
answers
56
views
Cropping a .usdz file
I have a program that is creating usdz 3D models from real world objects. I would like to be able to crop those objects in 3D space to remove extraneous nearby objects or walls. Is there a good ...
0
votes
0
answers
147
views
looking for meshlet generation algorithms
I am looking for algorithms to create meshlets from triangulated meshes.
I searched for articles, but could not find any.
Maybe "meshlet" is not the right term?
I want to cluster the faces ...
- 1,136
2
votes
1
answer
131
views
How is the alpha value treated when blending?
I'm struggling with understanding how blending works. Here's what I understand:
when I set the following
...
- 23
0
votes
1
answer
53
views
Rigorous example of early graphics system
Here is a paragraph of Shreiner and Angel's Interactive Computer Graphics:
"Early graphics systems used general-purpose computers with the standard von
Neumann architecture. Such computers are ...
- 101
0
votes
1
answer
167
views
Can I copy one texture to another perfectly with texelFetch()
Imagine I have two uncompressed, 2D textures A and B with identical sizes and formats. I bind A to texture unit 0, and B to a framebuffer object.
If I draw a full-size polygon in that framebuffer with ...
- 186
0
votes
1
answer
55
views
Recursive sampling in Marching Squares
So I just saw a video on Marching Squares by reducible, and I thought of a straightforward optimisation, but I couldn't find anything about it online. Basically here's the idea -
Start with a fairly ...
- 1
0
votes
1
answer
93
views
With a light source at (0,2,0) and unit cube (from [-1,1]) using a given shading formula, how is the r,g,b for each surface calculated?
The above problem is from a past Computer Graphics exam.
I am particularly confused about the explanation given, firstly for the top and bottom planes (since the direction of normal for top plane ...
- 3
2
votes
2
answers
234
views
How do I evenly subdivide the projection of a circle in 3D?
I want to draw a circle in 3D from line segments. There are plenty of examples how to do this with an even number of subdivisions in 3D space, but I want the minimum number of subdivisions to produce ...
- 121
0
votes
0
answers
45
views
Raytracing Diffuse Function not Working as Expected
I am trying to write a raytracing renderer using compute shaders in Metal. My implementation is based off of Peter Shirley's Raytracing in One Weekend: https://raytracing.github.io/books/...
- 1
0
votes
2
answers
89
views
How to extract region inside a loop on sphere
The input is a sphere(defined by radius and center) and a loop defined by a set of points(unordered, illustrated in cyan in the image above) that satisfy the implicit function of the sphere. How can I ...
- 31
0
votes
0
answers
48
views
Given 2d control points, how to write a vertex shader that evaluates a cubic bezier curve?
I need to write a program that evaluates a cubic bezier curve, using threejs and vertex shader.
I tried to calculate the bezier curve based on the x axis and the control points using the cubic bezier ...
- 111
0
votes
1
answer
420
views
OpenGL compute local size vs. performance
Does anybody know if using very small local sizes in compute shaders will hurt performance?
eg. If I do this in a shader:
...
- 186
0
votes
2
answers
258
views
OpenGL compute for sizes that aren't a multiple of "local_size"
I've been going round in circles trying to understand OpenGL compute shader "work groups" and it's doing my head in. It's all about as clear as mud.
In my compute program I have to set a ...
- 186
0
votes
0
answers
56
views
Interpolate Gradients to Vertices of triangular mesh
A well known way of interpolating the gradient field of a scalar field onto faces of a triangular mesh uses the following formula
(source: https://www.cs.cmu.edu/~kmcrane/Projects/HeatMethod/...
- 1
1
vote
1
answer
57
views
Numerically integratable fog volume feathering along a ray
I haven't been able to come up with a good solution for this myself, so I thought I'd ask if anyone else has any good ideas on how to approach this problem. Here's more or less what I'm trying to do ...
- 11
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votes
0
answers
56
views
Why do I get a black scene in OpenGL in Python?
I'm building a scene: a cylinder, and a torus and an icosahedron spin around it, enter the fog and exit the fog. Using a file with a fog texture (any). However, I get a black scene at the exit - why ...
- 103
1
vote
1
answer
75
views
Partial Workgroup release of compute shaders?
When using compute shaders, some workgroups can be faster than others, for example when all invocations within one group go into the 'if' case, where on another workgroup the invocations go into the '...
- 1,136
0
votes
0
answers
58
views
Calculating world coordinates of a pixel from a camera picture
Sorry for this question. I know there are many similar questions but I really know nothing about math that involves this case.
I have a picture taken from a camera. I know some information about this ...
- 101
1
vote
1
answer
80
views
Graphics API and double precision
For scientific reasons, we have to use doubles in our shaders. We don't need to talk about trying to store data in floating point numbers and so on.
I know there is special GPU hardware for double ...
- 1,136
1
vote
1
answer
200
views
Workgroup size performance change?
I know, that when using compute shader, the invocations should to be grouped with respect to a multiple of the hardware minimum workgroup size (Nvidia 32, AMD 64). Otherwise cores are blocked. In case ...
- 1,136
1
vote
1
answer
51
views
Distortion or Aliasing of a UV Sphere
I am trying to map a texture on a UV sphere. I created an algorithm to generate the vertices of the sphere and the UV texture coordinates for each vertex. How I do fix the distortion or aliasing?
The ...
- 13
3
votes
0
answers
54
views
Intel UHD extremely slow copy operations
Is there a way to make copy operations such as CopyResurce(d3d11) and glBlitFramebuffer(ogl) on multi-sample resources faster ...
- 367
2
votes
2
answers
192
views
3D triangle rasterization to voxels
Is there an algorithm to rasterize triangles into voxels (3D, not 2D) that is linear in the amount of voxels in the output?
I.e. given a triangle and a grid, generate the exact voxels that the ...
- 1,696
1
vote
0
answers
99
views
GLSL : Extremely slow compilation when using loop
I am making multiple gradients with GLSL. However, when I started using a loop instead
of a lengthy else if condition, the compile time jumped from 2-4sec to 40sec !...
- 111
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votes
1
answer
25
views
Is there a way to automatically optimize imags based on predefined marker on image?
Color correction is tricky. It's always a lot of work to make everything look same.
I have multiple products (clothing) to take a picture of. One is 100% red, other 100% Orange. Some are multicolor ...
- 103
0
votes
1
answer
90
views
Parametric equation for Catenary curve between two Points
I have two points in 3D space, A and B. I need to have a parametric equation of the catenary curve such that:
Cat(0) = A,
Cat(1) = B,
Cat(t)= f(t, A, B)
How can I derive the function f
