Questions tagged [algorithm]

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Deep Learning for 3D Point Clouds, volume detection and meshing

I'm working (as a Post-doc) on an archaeological excavation point cloud dataset with over 2.5 Billion points. This points come from a trench, a cuboid 10 x 10 x 3 m. Each point cloud is a layer, the ...
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2answers
65 views

Creating a Smooth 3D Mesh from a 2D Outline

I am trying to find (or maybe create) an algorithm for creating a smooth, rounded 3D mesh given a 2D outline. I'm trying to recreate a system from a Gamecube game called Amazing Island, and you can ...
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1answer
46 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 ...
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0answers
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 ...
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2answers
67 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 ...
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12 views

Area of a mesh patch given the corners

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/...
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47 views

Out of core rendering

Suppose there is a frame, which is larger that the device memory (I mean, dozens of Gb). And I would like to render to it from a set of textures, which is larger than the host memory (I mean, dozens ...
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1answer
252 views

How can i create a 3D Sphere(earth) using OpenGL, GLFW, GLAD, GLM?

Please help me out with this thing and currently i am a little more than a beginner so please tell me in that context. i don't need any obsolete methods for creating this like using GLUT or GLEW.can ...
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2answers
79 views

Techniques for rendering high polycount models

I would like to know what common techniques are used for rendering large models, when using rasterisation within a graphics API, for example OpenGL or Vulkan. For example if I had a model with >10 ...
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17 views

How can you use a rectangular object in an image and use its edges as a new coordinate system?

As a quality inspection vision application, we have images of printed circuit boards. The PCBs are rectangular in shape and the distance from the camera to the PCB is fixed. The relative location of ...
2
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1answer
63 views

Non jagged line algorithm for javascript canvas

I'm trying to draw a line between two specified points, by updating values in an array which is heightxWidth with each element a set of four bytes (r,g,b,a). In my naive implementation I get the top ...
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1answer
66 views

Why the Bresenham's algorithm does not work for those two points?

I am using the Bresenham algorithm from wikipedia: ...
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150 views

Pre-filtered environment map, deriving the equation

I'm reading through this article, and more specifically I'm trying to derive the equation that would explain the implementation the following shader (still in the same article): ...
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30 views

Arrange common items to spell out words

This seems like a pretty easy thing to do, but I've never done anything like it and I would rather not reinvent the wheel - so I'm looking for example code in pretty much any language or an algorithm ...
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1answer
35 views

How to scale primitive shapes [in Blender] so that they are within a [unit] sphere?

I wonder how is it possible to scale all shapes so that they are within boundaries of a [unit] sphere? I know how to do this for a cube: if radius of the sphere is S...
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0answers
154 views

HalfEdge data structure in openmesh, create_face function explanation

Does anyone have experience with open-mesh or computational geometry and can kindly explain what exactly happens in the function below? ...
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2answers
674 views

Very efficient/fast marching cube implementation

I was wondering if there's any known technique/algorithm that would compute a mesh generated by the marching cubes but hierarchically (like a divide and conquer strategy), in the implementation I know ...
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0answers
32 views

Help with efficient quadtree vertices indexing to avoid redundancy

I am creating a quad tree from ground zero, because I am going to collapse it from bottom up I am refining it with a certain LoD level. I am using glm for mathematics and opengl for rendering. ...
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48 views

Anti aliasing thin features in textures

Assume I have a texture with a repeating line pattern. The lines are exactly 2 texels wide (really thin). Ans very spaced out (50 texels in between each line). I am now struggling with the ...
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34 views

Mantiuk's contrast mapping seems to amount to a gamma correction

I'm reading this paper and one thing sticks out at me. Let's say I use the approximate transducer: R = 54.09288 ·G^0.41850 Then I scale it: ...
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2answers
122 views

What is a list of common, cheap, real time rendering algorithms?

I am well aware of the existence of Blinn-Phong shading, which is a great tool when you are doing, for example, modelling algorithms and wan't to focus on the model. In this case a full BRDF result, ...
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1answer
99 views

Tiled Image Palettization Algorithm?

In most cases today, image palettization consists of reducing the overall number of colors in an image to some fixed number globally. This is typically solved as a straightforward but computationally ...
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2answers
117 views

An algorithms for covering a 2d polygon with a predetermined number of rectangles?

I am looking for an algorithm that is able to cover with non-overlapping rectangles in a pre-defined number and minimum area a generic 2d-polygon. Polygons are usually free-hand draws, so they can be ...
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1answer
133 views

What algorithm is used in this animation from Tatami Galaxy?

Is there a name for this type of effect where many area sizes are increased/decreased in relation to each other? I'm looking for some type of algorithm, formula, logic, etc. for recreating this. Here ...
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1answer
42 views

Make a texture a clickable Button

What would be the best way to make a texture a clickable button? Suppose I have a Room (respresented by a 2D texture), where there are buttons. Would I in the main loop: check when the mouse is ...
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1answer
83 views

How to shift color values of a single RGB channel

I’m a weaver and textile maker with no prior coding or programming experience. In researching and reading through posts on this and other message boards, I was able to find a lot of useful information,...
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1answer
108 views

Bresenham's algorithm next pixel?

In line drawing, bresenham's algorithm was explicitly derived for lines with slopes between 0 and 1 in the first octant from point P1 to point P2, where the x value of P1 is less than that for P2. In ...
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2answers
932 views

Why are oct trees so much more common than hash tables?

When reading papers I commonly find Oct tree implementations of geometry representations to sort the data. However whenever I think about the problem hash tables seem better overall. Hash tables have ...
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2answers
788 views

Z-Buffer algorithm vs Painter's algorithm?

In hidden surface removal, how does the Z-buffer algorithm work vs. painter's algorithm?
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1answer
251 views

Flood-Fill and scanLine algorithms are line-based floods but I want square based floods

I have a flood-fill algorithm (Flood-fill) to fill a 24x24 matrix as follows (matrix is 24x24 here but will be much bigger in production): ...
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0answers
26 views

How can I register an articulated model to noisy predictions?

Given point sets $Y$ and $M$, I'd like to register articulated $M$ to $Y$ without changing the edge distances of $M$. The point correspondences between $Y$ and $M$ are known and points have a fixed ...
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0answers
42 views

Why the interval for which there are more number of steps is chosen while implementing DDA Algorithm?

I was studying the DDA Algorithm and learnt that initially we calculate both the x-difference and the y-difference between the start and the end points of the given line, and if dx > dy, we choose ...
2
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1answer
145 views

Deciphering Affine/Projective Transformation Code

I've spent about 2 days trying to understand this piece of code (from here) that applies an affine/projective transformation to an image. I will link bits of the code that I'm struggling to understand ...
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0answers
66 views

Cem Yuksel's “Mesh colors” implementation/demo?

Are you aware of any sample implementation or demo application of Cem Yuksel's "Mesh Colors" or "Mesh Color Textures" (http://www.cemyuksel.com/research/meshcolors/) ? The author does not provide any ...
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1answer
472 views

Feeding vertex data to a compute shader

I'm writing a CAD program in vulkan. In my current design, I have line paths represented as large vertex buffers for rendering. I would like to implement an algorithm for extruding the path outwards, ...
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1answer
467 views

How can I draw a filled circle on a grid with the less rectangle as possible?

I have a grid with a variable width/height spacing. Let's say 100 horizontal lines separated by 80 pixels and 100 hundred vertical lines separated by 50 pixels. Each cell of the grid in my logic have ...
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0answers
29 views

How are non-triangular wavefront meshes handled?

I have a wavefront loader, however it only works with triangular meshes. I have been trying to think how to handle faces with arbitrarily many vertices but I have no idea how they are to be handled ...
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3answers
215 views

How does the Painter's Algorithm handle transparency?

I was wondering if anyone could explain how the Painter's algorithm would handle transparent objects? Can the Painter's algorithm handle transparency?
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1answer
625 views

What is the use of epsilon in the Möller–Trumbore intersection algorithm?

The Möller–Trumbore intersection algorithm compares the determinant with an epsilon. What is this epsilon and how is its value chosen?
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1answer
165 views

How to test my triangle intersection implementation?

I've been thinking about this question for a quite long time.And my implementation seems to be correct for some cases but wrong with few others. How can I comprehensive test the algorithm? Is there ...
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1answer
87 views

Quick 2-color quantization for small images

So I have a small (8x8 pixel) image in 24-bit color. I want to be able to (quickly) generate a color-quantized version of the image that only has two colors. One naive approach is to cluster a luma ...
4
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1answer
130 views

Can someone explain this formula for parse RGB to HSL?

Im trying to complain the algorithm to calculate the HSL value form a RGB color. I understand the algorithm for the Hue, but im lost with the Lightness and saturation. Someone can explain why? There ...
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0answers
81 views

How to guarantee rasterization of triangles in a voxel representation

There are 2 problems i am trying to solve involving rasterization of geometry in 3D. The first is, my 3D texture is created with a top down viewd, so triangles that are perfectly orthogonal to the ...
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0answers
38 views

Which vertices to use to create side of model

I hope I'm asking on the right StackExchange site. Apologies if I'm not. I want to generate 3D triangulated models of optical lenses, circular in shape. I can create the meshes for the front and back ...
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1answer
95 views

How to obtain a parametric equation out of a part designed in Autodesk Inventor?

Whenever you make a part in inventor, the software calculates de properties of the whole body given a constant density. Then, automatically, it shows the inertial tensor. As you can recall from math, ...
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1answer
266 views

How to smooth out a voxel grid?

So I am facing the following issue. Say I have a minecraft like mesh (i.e I have a bunch of cubes on top of one another). I wish to smooth out this mesh in such a way that only the regions where ...
2
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1answer
116 views

how to build the feature curves of this algorithm?

I hope this is the right group to be able to expose my doubts about the implementation of the algorithm shown in this article. The question I have is how to do the feature curves, what I do not ...
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1answer
438 views

Simple Intersection Algorithm for Ray and 3D Bézier Curves of Varying Thickness

I'm trying to get an algorithm for intersecting a "tube" (a 3D cubic Bézier curve extruded by a possibly-changing radius) with the following required properties: Computes intersections of ray and a ...
4
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1answer
295 views

How to calculate curvature of isoline of image

I've got a discrete grayscale image (a.k.a. 2D rectangular array of floats). Its continuous representation (whether received via reconstruction with sinc, with a cubic kernel, with a triangle kernel......
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3answers
2k views

How to modify Perlin (not simplex) noise to create continental like terrain generation

I have been playing around for a day with Perlin noise, and I am currently stuck. Most of the modifications I have made to the algorithm produce more or less the following: Now, this is a very good ...