Questions tagged [interpolation]
The interpolation tag has no usage guidance.
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Spline interpolation library in cpp
Have been searching a lot for a good spline interpolation library in cpp, came across one, which is the famous Eigen library , having the unsupported counterpart for spline fitting.<Here>.
I ...
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2answers
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How to do linear interpolation?
Here in my book they have shown interpolation using parametric equation of line but I am unable to figure out how do they found out t=|y1-ys|/y1-y2 , t=|AD|/|AB| , t=|CE|/CB ,t=|EP|/|DE| here is the ...
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1answer
91 views
Determining Rational Quadratic Bezier Curve Weights for Circle
I am trying to create a spherical interpolation with 3 points. I'm currently using Quadratic Bezier Interpolation but have been told I should use Rational Quadratic Bezier Curve in order to get a ...
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1answer
95 views
How to interpolate vertices when clipping?
When we clip in homogeneous clip space, we have to generate a new vertex located at the intersection between the edge and the clip plane. We thus have to interpolate the $(x , y, z , w)$ position of ...
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How to interpolate vertex while clipping in homogeneous clip space?
I want to clip triangles to the near plane, in homogeneous clip space, so for each edge, I have to see if it crossed the near plane. If it has, I linearly interpolate the two endpoints based on the ...
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How could I remove this colour interpolation artefact across a quad?
I've been reading up on a vulkan tutorial online, here: https://vulkan-tutorial.com. This question should apply to any 3D rendering API however.
In this lesson https://vulkan-tutorial.com/...
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1answer
87 views
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 ...
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258 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. ...
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1answer
234 views
Interpolation in Graphics Pipeline
I am trying to program my own version of WEBGL graphics pipeline in python, however, I am confused as to where the color interpolation takes place in the pipeline. According to my research, it happens ...
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45 views
Interpolating HSV color with black
I'm interpolating RGB values by transforming them into HSV space and then back into RGB. I have trouble figuring out how to achieve ...
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58 views
Is linear interpolation in a 2D texture possible (not quadratic like bilinear interpolation)?
I am currently studying for a computer graphics exam and on the slides about bilinear interpolation it is said that it is in reality quadratic interpolation.
An (on the slides) unanswered question ...
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Irradiance field approximation with black probes
I'm posting here after some time searching the Internet and reading presentations and papers, to find out the best options to solve the problem I have.
I'm implementing irradiance field with ...
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1answer
210 views
computing derivatives of sampled data
I am trying to calculate the derivatives of a sampled data set by following an example in this book. The data is a set of 2d quads(green area in below) and their vertices(4 each). The data is in the ...
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55 views
Vertex positions from particle position
I have a question about Nvidia Flex or any particle based simulation in general:
The particles are created by sampling the mesh, which can result in fewer particles than there are vertices in the ...
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2answers
198 views
How to calculate interpolation between multiple skeleton poses?
I found out that I should use spherical linear interpolation to blend two poses of a joint. I cannot find what to do if I have hundreds of poses to blend except applying the SLERP iteratively.
What ...
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354 views
Lanczos filter implementation issue
I tried to follow Nathan Reed post Antialiasing: To Splat Or Not to implement splat method. The image I am getting thorugh the Lanczos filter is very different than Nathan. I do not understand where ...
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1answer
608 views
Texturing an “infinite” plane
I am rendering an infinite plane as described in the following answers:
https://stackoverflow.com/questions/12965161/rendering-infinitely-large-plane
https://stackoverflow.com/questions/7380250/how-...
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1answer
87 views
Choosing corner values for trilinear interpolation
I'm caching distances for SDF functions in volume textures for faster rendering, and I'd like to use trilinear interpolation for smoother edges. I know that I'll need distance values at each corner; ...
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2answers
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ScratchAPixel : Understanding how to use Perlin's permutations hash table
Consider this course : https://www.scratchapixel.com/lessons/procedural-generation-virtual-worlds/procedural-patterns-noise-part-1/creating-simple-2D-noise . In sub-part Introducing the Concept of ...
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Why my cosine interpolation of a cube's face doesn't work?
NB please : executable use cases are available at the end of this question. I begin this question by showing you the problems of my program, then I explain how the latter works, and finally I end up ...
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215 views
Using GPU instead of CPU in Scala
I wrote a program that displays points expressed in 3D in a 2D canvas, using perspective projection. The aim is to display a cube. Each face of the cube is drawn by linearly interpolating the points ...
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1answer
346 views
How to deal with light leaks?
I'm struggling with light leaking through meshes (especially thin ones) due to interpolation between probes located on the opposite sides of those.
First approach I took was mapping all static ...
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2answers
648 views
Geometric interpretation of this bilinear interpolation equation?
Bilinear interpolation can be achieved by interpolating two values across the x axis, and then interpolating between the results across the y axis, like in the image below (from https://blog.demofox....
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1answer
267 views
How to obtain generalized barycentric coordinates for n-sided polygon?
Quadrilateral linear basis functions(generalized barycentric coordinates) are defined as:
What are the steps to calculate the above functions?
Is it possible to obtain basis functions for a 5 sided ...
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196 views
Sinc interpolation and Ideal reconstruction example
I am trying to apply sinc interpolation on this data set. The patches in the left image is a snapshot of AutoCAD 3d faces. Lux values are calculated for centre of each patch that are in 0.3m x 0.3m ...
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1answer
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The mathematics of two dimensional interpolation on a quad
I am trying to wrap my head around how exactly the GPU interpolates texture coords on a quad. I realize to the GPU a quad is two triangles but I find thinking in terms of the whole quad to be easiest.
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822 views
Bilinear Interpolation
I am trying to implement bilinear interpolation as described in the paper Spatial Tranformer Networks by Jaderberg et. al (see link to paper). They describe bilinear interpolation in Equation 5 as:
$$...
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66 views
General interpolation practices
Say my animation scenario contains one mesh interpolating into another (possibly approximating over other meshes), using Bezier curves.
I know that for smooth surfaces, where normals can be ...
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0answers
83 views
Interpolating normals during animation
I'm doing linear tweening of a cyllinder to a cone of equal radius and height in OpenGL. I know parametric equations of both of them, so I derived vertex normals accordingly. Now, I know, that proper ...
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1answer
3k views
How are mipmap levels computed in Metal?
My question is specifically in regards to Metal, since I don't know if the answer would change for another API.
What I believe I understand so far is this:
A mipmapped texture has precomputed "...
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1answer
701 views
Perlin Noise with Smooth function vs Lerp
I tried implementing Perlin Noise using the Wikipedia as my main resource. From what I can tell my implementation of the ...
2
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1answer
175 views
What is a common approach to smooth structures in textures?
I have a screen-aligned texture resulting from multiple rendering passes. It looks about this:
I want the edges to appear smoother than they do now (but still keep their characteristic shape). When ...
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0answers
33 views
Make 3d objects from 3 projections in 3D Studio Max
In the early 3D Studio days before it got Max in its name it was possible to make a 3d object by defining its projections in xy, xz and yz plane. 3ds would then interpolate a 3d object from the ...
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1answer
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Normal Interpolation for Phong shading
As the title says I have been trying to understand the normal interpolation for the Phong shading/lighting model. I am unsure of the equation to calculate the normal but I have come across this ...
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1answer
313 views
How to use Monotone cubic interpolation in 3D?
I wanted to use Monotone cubic interpolation, but the site only provide explanation for 2D case. How can I extend it to 3D?
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2answers
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How do I use barycentric coordinates to interpolate vertex normal?
Given a triangle and a point inside the triangle in Cartesian coordinate system, I compute the Barycentric coordinate of the point like this:
...
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1answer
767 views
Screen coordinates, barycentric coordinates and global coordinateas
To continue with this my other question, here's the problem. So, I've a slide, which I'm trying to understand.
Here are my questions.
What are the barycentric coordinates of? From my previous ...
5
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1answer
214 views
How to rasterize a line when the background color is not always white?
I've to rasterize a line taking into account not only the background color of the screen, which is white, but also the color of other objects in the scene. In my case, I've just another object, a ...
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3answers
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Does the blending matrix change between calculating various curve segments in a uniform cubic B-splines approximation?
I would like to ask about uniform (periodic) cubic B-splines (approximation, no interpolation).
$$B=1/6\begin{bmatrix}-1&3&-3&1\\3&-6&3&0\\-3&0&3&0\\1&4&1&...
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1answer
405 views
Creating a gently moving 2D fog effect
I am trying to create a fog-like effect, similar to that found using perlin noise. I know where I can find information about that effect, but it's harder for me to tell if it's an efficient route for ...
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1answer
487 views
Image rescaling algorithm
Suppose I have to use bilinear interpolation to rescale image. I more or less understand how enlargement works in case of integer scale factor.
But what to do with non-integer scale and especially ...
3
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1answer
286 views
Find closest point on surface interpolated by 2d matrix of points
I have rectangular matrix of 3d points sampled from a parametric surface. In my program this matrix provides base points for bilinear interpolation of surface (In any (u,v) point it returns 3d point ...
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1answer
429 views
How can you interpolate over an array of say 5 colors?
I have an array of color values. I have an interpolating parameter, t, which varies from 0 to ...
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231 views
How to do keyframe interpolation on matlab?
I want to do keyframe interpolation in matlab.
If I understand correctly, it uses splines to approximate the the motion of specific pixel points within the frames(through transforms). Correct me if I'...
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2answers
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What is bilateral upsampling?
I've worked with various interpolation algorithms including linear, cubic (and bilinear and bicubic), other bezier (and nurbs, etc) based interpolations, lagrange interpolation and some others, but I ...
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1answer
542 views
Perspective correct interpolation of normal values
I'm currently writing a software rasterizer and I'm at the point where I can draw arbitrary triangles with vertex colors and perspective correct texture mapping. I do point and directional lighting by ...
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1answer
1k views
Is there a way to interpolate color across the line with only integer calculation ?`
Here is my function that does interpolation
...
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2answers
1k views
Linear interpolation on Plane (Marching Cubes)
Let's assume I have the following cube.
Let's assume the isovalue = 0. I would like to draw the resulting triangles of the isosurface.
I know that first I define which values are inside or outside ...
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0answers
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Which interpolation algorithm does MS Paint on Windows 7 use for image rescaling?
I was about to scale this image down to 64x64 pixels:
The result I got on MS Paint on Windows 7 was surprisingly good (i.e. crisp edges):
, whereas scaling it with GIMP resulted in for cubic and ...
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1answer
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Interpolating vectors on a grid
If you have values on a grid and you want to find the value of a point within one of the cells, you can use techniques like bilinear or bicubic interpolation to get the data at that point.
What ...
