# All Questions

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### I have found that the Gloss is the inverse of the roughness. Will simply inverting the gloss map work for roughness

I am using Substance Painter and an Adobe Fuse character. Fuse outputs a gloss map, and sp wants a roughness map. Would inverting the colors in a program like Photoshop work to switch it over?
50 views

### SDF collision detection

I was wondering if there are any techniques for calculating the intersection point/s between two or more distance fields.
35 views

### Change of speed but no change of size after OpenGL Perspective Projection

I am new to OpenGL and I am trying to code un optic flow with dots appearing from the background and moving towards the viewer. As a consequence of a perspective projection, the dots are faster and ...
57 views

### What is the difference between post-/pre- sampling, aliasing, filtering and processing?

What is the difference between post-/pre- sampling, aliasing, filtering and processing? How do the terms post-/pre-aliasing, post-/pre-processing, post-/pre-sampling and post-/pre-filtering relate to ...
53 views

### Color shading and light calculation for ray tracing

I am currently building a ray tracer and I came across a problem and confusion regarding the light calculations. For lighting, I am using the following mathematical model: Where ...
75 views

### Calculating the angle between two polygons

For my application, I want to render models as polygonal surfaces in 3D space and have edges that are bent "outwards" to have a solid line and those who are bent "inwards" to have a dotted line. So if ...
46 views

### In what scenarios and how does GL_ARB_buffer_storage help performance?

The Dolphin emulator for GameCube/Wii has the ability to use the ARB_buffer_storage (or EXT_buffer_storage for GLES) to improve rendering performance. From the extension's description, a GPU driver ...
38 views

### Multiple Importance Sampling in Bidirectional Path Tracing

I'm trying to understand the computation of the path density described in the book Physically Based Rendering. They assume that a path $$x=(x_0,\ldots,x_{n-1})=(q_0,\ldots,q_{s-1},p_{t-1},\ldots,p_0)$$...
25 views

### Framebuffer not detecting image

The command, fb-test -f 0 generates and displays a test pattern on the screen. But, the command, ...
21 views

### Converting one png file into multiple SVG files

I have the following image which I would like to turn into a font: I can easily turn it into an svg with pngtosvg.com, but the result is only a single group. I'd like the result to be multiple groups ...
61 views

### Camera Implementation without Limitations

I've developed a simple (Third-Person) Perspective Camera with Orbit controls. However, my implementation doesn't handle the case where if the pitch goes over 90º it flips upside down. From what I've ...
24 views

### Is there a way to animate 'Tiling' of UV map using GLSL or Shader Language?

I'm looking for a way in where I could not only change the Texture UV Map 'Tiling' inside of Unity, but animate it by just having the 'X' go back and forth now and then from like 0.98 to 1.02 or ...
58 views

### Blurring image with RGB values without convolving it with a kernel

I'm using an app for face redaction that doesn't allow access to the source code but only allows me to pass pixel values for red, green and blue channel upon which it creates a matrix with the same ...
20 views

### What quad will fill the screen, which can be inverse-projection-view transformed to map to the near frustum plane?

I've been experimenting with raytracing using GLSL. I had success rendering a cube which encloses the object. Now I want to do a full-screen raytrace, and I want to construct a quad which covers the ...
21 views

### How to visualize a dataset , generated in curvilinear grid, in opengl with texture maping?

I have a dataset obtained from astronomical simulation. This data was created in a curvilinear grid with polar coordinates. The form of this dataset is a simple array (1d) of intensities, i can ...
64 views

### FXAA vs MSAA on modern hardware

looking for suggestion whether it is worth implementing a post process FXAA pass on modern mobile GPU's (mainly looking at apple A Series chip), or should i simply use the MSAA. Did a basic test with ...
26 views

### Probability of choosing the current strategy in the pbrt implementation of Multiplexed Metropolis Light Transport

In the description of the Multiplexed Metropolis Light Transport implementation of pbrt it is claimed that "the inverse probability of choosing the current strategy $(s,t)$ [...] is equal to <...
46 views

### Can pixels on the image plane be mapped to world space coordinates?

I'm trying to learn the fundamentals of 3d computer graphics by writing a toy framework in WebGL. I'm currently working on mouse based camera controls. There are plenty of good resources in the ACM ...
43 views

### Weird Ray tracing artifacts when Code run on widows

I am trying to create a raytracer following peter shirley's in a weekend series. I am getting weird color distortion artifacts when I am running the code on windows. However, the code runs fine when ...
37 views

### Stecklov operator vs Laplacian operator

There's one paper published at siggraph that captured my attention : Steklov Spectral Geometry. I'm not an expert in geometry processing, but I'm trying to learn as much as I can. You can easily read ...
31 views

### What is performance better - add four materials to mesh or duplicate every vertex and use packed texture?

I am making ski jumping game (in Unity) with procedurally generated hill mesh. I want to add lines on hill like this (mesh is created by script, but I've manually assigned materials in Blender) ...
84 views

### Why cubic curves provide the minimum curvature interpolants?

As described by Shirley in his computer graphics book, Cubic curves provide the minimum-curvature interpolants to a set of points. That is, if you have a set of n + 3 points and define the “...
45 views

### Roughness Value of (Close to) Zero in Physically Based Rendering

In my Direct Light Physically Based Renderer, when I set the roughness too low (ie. 0.0 or close) the specular reflection doesn't show, not even at high resolutions and at perfect angle with the ...
22 views

### Disable both depth clamp and depth clip in Vulkan (older drivers)

I'd like to store arbitrary float depth, so I have to disable both primitive clipping and depth clamping. I can disable clipping by setting ...
57 views

### map 16-bit integers to RGB colors with monotonic relative luminosity

Red, Green and Blue apparently contribute differently to the luminosity perceived by humans: https://en.wikipedia.org/wiki/Relative_luminance I am trying to find an algorithm to map unsigned 16 bit ...
45 views

### Estimating the position of vertexes in a 3D model

Introduction to my project: We are machine learning scientists and working on a biomedical system for tracking tongue for speech pathology using a technology called EMA (Electromagnetic ...
44 views

### Trading off instancing for render order

I've been doing some searching online and it seems like I could improve my renderer by ordering my draw calls based on depth. For opaque objects render the closest items first and move backward in ...
78 views

### How RGB images are formed

I have a noob level question about RGB images- Pixels in RGB images are in the range of (0-255), so technically each channel ranges from 0(black) to 1(white), then why we say that each image has a Red,...
56 views

### Tessellation Speed in terms of interpolated points per second

For a research project, I have written a Tessellation Shader to interpolate solution points of a 3-Dimensional mathematical equation. Therefore I don't use any techniques for displacement, I merely ...
77 views

### Want to study computer graphics

I want to study computer graphics but I don't have a strong foundation in mathematics. I am doing a computer science degree that doesn't cover computer vision, image processing or computer graphics, ...
27 views

### Deskewing and Cropping Scans using ImageMagick

Attempting to deskew and crop scans of a CD booklet using ImageMagick. Here's one image which I've been using as an example on which to build my one-liner - https://mega.nz/#!jIQD3aqC!PbjG4_Xaq-...
68 views

### Why is OpenGL recompiling my depth map vertex shader based on the GL state?

I've written a shader that writes depth to each face of a cube map, as part of rendering cube map shadows for a realtime 3D engine I'm writing with OpenGL and C++. The shader transforms each vertex ...
72 views

### Do I need a normal matrix if I calculate lighting in an objects space?

As a quick reminder, here is what normal matrix is and why do we need it. Now the question - if I take the light position and transform it into an object space than I don't need the normal matrix at ...
37 views

### Difference between Passing Instance Data to Vertex Shader methods

I see two kinds of passing Instance Data to Vertex Shader in different Examples. 1 .Using a Uniform Buffer and filling in an array, like below ...
12 views

### How can I detect if an edge has flipped during the UV unfold process?

I'm writing my own UV Unfold operation (similar to Maya's Optimize UV tool or 3DS Max's Relax Tool). My code works great 90% of the time but in some instances, I'm getting faces and edges that flip ...
37 views

### Inverse texture mapping

I have a textured 3D object and looking for ways to transform back the texture. Effectively, I think this is an inverse texture mapping task. Do you know of anything close to this? Some papers or ...
55 views

### Are there any reasons to use power of two textures with modern mobile platforms?

Are there any reasons to use power of two textures (like 128x128 sized) if one targets modern mobile platforms (with OpenGL ES 3.0, Metal and/or Vulkan)? With iOS the PVRTC only supports power of two ...
57 views

### How to approximate the heightmap of processed wood?

In the above image, you can see that there is some slight variation of the height of each wood plank. These variations do NOT come from the wood texture itself, but from the way it was cut, i.e if a ...
52 views

### Understanding the irradiance map generation

I am trying to understand how the generation of irradiance maps works. I was reading LearnOpengGL tutorial and Codinglabs article. Reading those articles, I got a bit confused about how we use ...
32 views

### How to display image from CUDA / What API to port my project to for real-time raytracing?

I started a raytracing project using the python numba library which provides a just-in-time compiler for CUDA kernels. When the scene is rendered my result is a 1920 x 1080 x 3 RGB array in GPU memory....
78 views

### Compute shader only 5 times faster on the GPU than on the CPU

I'm running following compute shader in Vulkan. worldImage is device local memory that holds the world. resultImage is reference to the memory of the swapchain image: ...
53 views

### Pitfalls of animating with quaternions

When working with animating a rig, quaternions are often used for rotations. However sometimes we need to clear rotation along given local axis of a joint. With quaternions it's not as simple as just ...
61 views

### Convert triangulated object to a polygonized object

Is there an efficient algorithm to convert a 3D object described with a set of triangles to a 3D object described with a set of polygons. Polygons can have an arbitrary number of points, more is ...
22 views

### Image contribution function and reconstruction using filters

So I've been reading Physicall Based Rendering which in section 16.4.3 defines the "image contribution function" to be the following $$I_j = \int_\Omega h_j(X)L(X)d\Omega$$ where the variables are ...
46 views

### Help with understanding the look-at function (the view matrix)

I've been reading this article about the look-at function. I don't understand the part when they're trying to inverse the matrix N. They say that R is orthogonal because all its row and column ...
43 views

### Only each third image in swapchain is being used, causing flickering

I've managed to write a "small" Vulkan program that outputs a solid color using compute shader directly to swapchain. However, it doesn't work properly. ImageMemoryBarriers I've setup don't ...
56 views

### Weird glColor3f results in framebuffer objects

The code is glColor3f(1, 1, 1); gluSphere(gluq, 0.2, 10, 10); glColor3f(1, 0, 0); glTranslatef(1, 0, 0); gluSphere(gluq, 0.2, 10, 10); In short, when I draw ...
40 views

In newer OpenGL it's encouraged to use shaders and pass the model-view-projection as parameters. But what if I drew a complex object, and wanted to translate/rotate it and draw many copies? For ...
I have a mesh $\mathcal{M}$ and 4 vertices $v_1, v_2, v_3, v_4$, I know the connectivity but not the geometric path. $\mathcal{M}$ is a single connected component (with no holes). What's the quickest/...