# All Questions

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### Interpolate vertex attributes with $z$ AFTER homogeneous divide

Usually, if we want to interpolate some vertex attributes, say $A_1$, $A_2$ and $A_3$, we have to first divide them by their corresponding $z$ in view space, then we interpolate them using barycentric ...
9 views

### Albedo image map to color's Light Reflectance Value (LRV)

In many datasets in the literature of both Computer Vision and Computer Graphics there is the albedo map of a scene represented as RGB images, which in principle corresponds to the diffuse reflecting ...
26 views

### Paint pixels on the image around the cursor for painting application

I'm trying to create a simple painting application. And I was wondering about an efficient way to draw pixels on the screen. I have a pixel struct: ...
38 views

### Get normalized device coordinate of an image pixel

I have an image rendered to the screen, and based on the normalized device coordinates of the cursor I would like to pick the pixel of the image under the cursor. Say the image has four channels, I ...
21 views

### GLSL asymmetric performance for point cloud

I'm currently using OpenTK (OpenGL binding for C#) to draw a lot of points (~17 million) - that very rarely change - in a cube (256 x 256 x 256) with different float "transparency weights". ...
31 views

### How to find closest points on two not intersecting convex polygons in 2D

I would like to know if it is possible to do this using GJK alghorythm. I know how to find if polygons intersect and also find closest point on polygon from a given external point. Using Minkovski ...
7 views

### MMP algorithm, no metion of “in window” intersections

If you are familiar with the MMP algorithm for geodesic finding, you know an important part of the algorithm revolves around solving intersections of windows. I am running into a case that I don't see ...
29 views

### Are there algorithms besides Canny edge detection that can create consistent width edges?

Sobel edge detection is pretty much the quintessential way to get edges out of an image. It however suffers from certain quirks. One example is, because it's gradient, based certain surfaces exhibit ...
30 views

### Why isn't the 'Map Colors' fixup changing text colors?

I saw this question some where, I think Reddit, but I can't find it. I have same issue. Please see the screenshot beneath. I've uploaded the PDF to mega.nz I'm using Adobe Acrobat Pro DC Version 2019....
235 views

### Why is eye-based ray tracing preferred over light-based ray tracing?

It seems that virtually all path tracers use eye-based or view-based path tracing. That is, the light rays originate from the camera rather than the light source. The reason given for this everywhere ...
20 views

### Deferred Decals

What's the proper of way of calculating the coords to apply decals by let's say linear interpolation? My understanding is that you render your GBuffer albedo, specular, etc... and after that you do ...
13 views

### Get binding point of sampler/image in shader

I have an image and a sampler declared in a shader as follow layout(binding = 5) uniform isampler2D heightmap; layout(binding = 3) uniform writeonly uimage2D info; ...
56 views

### Let GPU write to itself

As someone who is trying to dive into WebGL for parallelizing simulations, or Machine Learning, or typical IIR filters I've come to realize that for everything that I want to do requires the GPU to ...
23 views

### Does ffmpeg or NVDEC (nvidia decoder) support YUV444 video input?

I tried feeding an .h264 video with YUV444 color format to ffmpeg in hardware decoding mode on a GTX 1660 and it looks like this color input isn't supported. I get an error in the ...
36 views

### Clipping 3D Perspective matrix

I am trying to implement clipping in my simple renderer, but i have a trouble with setting the boundaries. I used the same projection matrix that is in OpenGL. The problem is, the vertices that are ...
31 views

### OpenGL shader introspection/interface queries for images

I've been looking at Interface queries in order to prevent common mistakes that are time consuming to debug, such as forgetting to bind a buffer, binding the wrong resource type, etc. However, I wasn'...
43 views

### Is it possible to send Texture Buffer to shader dynamically?

I want to send a series of integer to the geometry shader, while the data will be modified every frame. But when I try to retrive the sampleBuffer in geometry shader, it seems to keep output zero. Am ...
42 views

### alternative to spherical harmonics to model radiance aproximation, optimized for real-time evaluation

I'm looking for a compact representation of radiance over the hemisphere that is also performant to evaluate in realtime (in a pixel shader). The purpose of it is to compress surface lightfields so ...
54 views

### Transfer the texture between two different sets of uv

Say I have a mesh with two sets of uvs. And I have a texture made for the first set of uvs. I would like to create a second texture that has the same relationship between its pixels and the second set ...
49 views

### How to retrieve data from Compute Shader to CPU?

I want to retrieve data that has created by the compute shader but have no clue how it works. After researching a few forums and articles on how it should work and this is what I came up with. Compute ...
85 views

### Procedural generation of biological models

I was wondering if anyone can point me in the direction of some research papers, or articles that describe a method for generating biological 3D models. I am drafting a prototype for a new game that ...
20 views

### What method is used for baking grayscale curvature maps

I'm looking for a way to generate curvature maps like this: The map stores the Convexity and Concavity of each pixel as a value from 0 to 1, where .5 is no curvature and 1 and 0 are the extremes. I ...
70 views

### Approximating Geodesics in a half edge DS, how can I refine my mesh to get good approximations

I implemented Djikstra's shortest path algorithm to approximate Geodesics on arbitrary meshes. Djikstra's works, but I noticed a problem inherent to the discretization of my meshes. Consider the ...
57 views

### BRDF for point lights should not return values over 1

This is standard Cook-Torrance BRDF in formulation for a single point light. No intergrals over a hemisphere, just a single direction to a source of incoming energy.  L_o = { \bigg ( (1-F) \frac{...
90 views

### Corrupt values when writing and reading from the same RWTexture2D in HLSL/DirectX?

I'm playing around with DirectX 12 ray tracing, and I'm trying to read and write data to a 32-bit RGBA floating point RWTexture2DArray within a DirectX 12 HLSL shader. I'm getting weird corruption/...
48 views

### Phong model: why no multiplication by N dot L in specular term?

Classical Phong reflection model, as described on wikipedia, computes diffuse and specular light as follows: ...
57 views

### Does atomic functions on same memory location cause an performance issue?

is it worse to do for each invocation an atomicAdd on the same memory location than doing for each invocation an atomicAdd to a unique memory location? (I know, atomicAdd does not make sense when each ...
50 views

### Conditionals and branching in shaders

This is a quite wide subject which implies a lot of topics such as the platform or the compiler, but I think that it could be useful for everyone to know more about this. A common mistake is to think ...
64 views

### How are textures projected onto 3d models in texture painting applications

In most modeling software you can texture paint onto 3d models using so called stencil textures. They basically project a texture from the viewport view onto the model as seen for instance in the ...
46 views

### Aligning (matching) colors (white balance, brightness) of two scenes based on reference object

What I am trying to do is to become able to compare with reasonable accuracy two real world fabric/textures (colorwise speaking) at two distinct locations. I can't move them into single place to ...
37 views

### Reading from buffer versus calculating on the fly performance

I am creating a fast fourier transform algorithm for the compute shader - i am no expert on how GPUs really run optimally so thought i would ask here. I have the option to calculate on the fly or ...
40 views

### When unsetting a VAO, should you also unbind the associated VBOs?

I'm working with a js/wasm/c++ program that uses object oriented programming when updating the OpenGL state. There are corresponding c++ classes for VBOs (vertex buffer) and VAOs (vertex array). ...
40 views

### What's a good research topic in Computer Graphics?

I am currently trying to find topics for my master's thesis. I would really like to do something in the field of computer graphics, but I've been having trouble finding what are some current problems ...
41 views

### How do you apply a normal map to a 3d mesh?

I'm writing my own mesh renderer, and I previously was able to apply a normal map to a sphere, so I understand the basic process of applying a normal map. But my understanding is that in order to ...
23 views

### Efficiently generating mesh for self-generated voxel grid

I'm working on an app that lets users construct a 3D house, with the ultimate goal of it being 3D printable. I use various materials in the form of a height map constructed from an image, like this ...
34 views

### Where to get BGFX documentation

I'm creating a 2D game engine similar to the design of Undertale, and I decided to use BGFX as a 2D rendering library. The only problem is, I can't find any documentation for this thing. All I want is ...
28 views

### OpenGL Framebuffer with multiple Depthbuffers inside

I am trying to put multiple depthbuffers into one Framebuffer. I want to use VR and render both eyes at the same time: that means, in the geometry stage I want to clone the incoming triangle to two ...
24 views

### Two questions: How to find the last 3 points for Milne's Predictor? And methods for smoothing iso-line contour?

I am trying to implement Milne's predictor method to solve the eq. for iso-lux contours according to this paper by Arvo. Here is the predictor: From the paper: "It is a multistep method that ...
36 views

### UV partial derivatives of a cylinder shape primitive

I am new to rendering and I would like to calcualte UV partial derivatives of a cylinder shape, which is parameterized by radius $R$ and length $L$. Using cylindrical coordinate mapping, for a surface ...
88 views

### Why negate z when constructing projection matrix OpenGL

I constructed an orthographic projection matrix from this article on scratchpixel.com: ...
27 views

### Draw Line on Arbitrary Surface

I'm working on a 3D modeling tool and we use data from OpenLayers to construct a 3D mesh of some land. I want this behavior: you click on the mesh and it puts a point where you clicked on the mesh. ...
43 views

### Crystal ball rotation - I don't get why the code works

For context: I'm absolutely new to graphics programming and I've always had trouble getting the math. I had the task to write code for a crystal ball interface using OpenGL. There's an object in the ...
53 views

### Find the formulas of the middle point algorithm for drawing the parabola?

Find the formulas of the middle point algorithm for drawing the parabola ? x^2 = 4*(a+b)*y , a,b > 0. Solve it according to E(East) and NorthEast(NE) ? This is the result i got (This is writen ...
65 views

### How is orthographic projection used in computer graphics technically classified as a projection?

I'm wondering why the orthographic projection we use in computer graphics is called a projection, if all it does is just scale and translate a mesh? According to wiki orthographic projection is ...
81 views

### Perspective correct interpolation z-buffer

While I was deriving expressions for perspective-correct linear interpolation on triangles, I reached the conclusion that the interpolation may be kept linear only if view-space $Z$ is available. ...
52 views

### The ploygon width parallel to the x axis as a function of the y ordonate?

Considering a polygon with n vertices as input. I need to calculate the integral of the form $\int_A p(y) dA$ where $p(y)$ is a piecewise polynomial function of $y$. May be if I could find the ...
71 views

### How to scale signed distance field fonts properly?

I have a setup where I'm rendering a bunch of characters on a canvas with an SDF font. The users can zoom in to see the details of the smaller texts, but currently the smaller characters are quite ...
27 views

### Interactive point cloud

I’m trying to build an interactive point cloud renderer in Panda3D. I want to render a point cloud and be able to select a group of points and change their colors, maybe with a rectangular selector or ...
The following is an excerpt from a 2005 paper on geodesics on triangular meshes, taken from section 3.5 In this case $p$ is a point on some arbitrary face in a mesh, $p'$ is a point on one of the 3 ...