Questions tagged [interpolation]

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9 votes
3 answers
4k views

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 ...
0 votes
1 answer
75 views

Interpolating poisson disk samples in real time

If I have a regular sampling pattern there typically exist many reasonably fast ways to interpolate the results of the sampling procedure in between the sample locations. For example bilinear or ...
3 votes
1 answer
135 views

Smooth triangular mesh interpolation

I am looking for an algorithm which would smoothly interpolate triangles of a mesh (computed by Delaunay triangulation) where each vertex has some value (elevation in my case). I need it for PDAL ...
1 vote
1 answer
56 views

What causes blobby edges with alpha testing?

I'm trying to understand what causes the blobby edges when using alpha testing to create transparency with 1-bit alpha channels. The edges appear pixelated, but with rounded corners and diagonal lines....
0 votes
0 answers
42 views

How to interpolate between two MVP setups?

I am currently writing an AR experience. I have a Camera View Matrix, A Camera Perspective matrix and the Model Matrix of the content I display. The AR content should can be switched to "2D",...
2 votes
1 answer
106 views

Deriving formula for perspective correct interpolation

I am trying to derive the formula for perspective correct texture interpolation on my own while implementing my own software rasterizer (projecting an arbitrarily rotated triangle in camera space on ...
0 votes
0 answers
64 views

Methods to interpolate between 2 topologically identical 3D meshes

I have 2 3D surface meshes. These meshes have vertex-correspondence and have the same topology (same edges and triangles connecting the vertices). However, the vertex positions (3d coordinates) are ...
0 votes
1 answer
198 views

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 ...
1 vote
0 answers
125 views

Fake cubic Hermite spline interpolation with smoothstep

When scaling an image with Bicubic Interpolation, the Cubic Hermite spline interpolation is used. smoothstep is one of the four basis/blend functions of this kind ...
4 votes
0 answers
2k views

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 ...
0 votes
2 answers
124 views

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 ...
3 votes
1 answer
231 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 ...
4 votes
1 answer
185 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 ...
1 vote
0 answers
210 views

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/...
3 votes
1 answer
146 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 ...
4 votes
1 answer
696 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. ...
1 vote
0 answers
79 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 ...
3 votes
1 answer
532 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 ...
0 votes
0 answers
76 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 ...
2 votes
1 answer
333 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 ...
3 votes
0 answers
112 views

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 ...
2 votes
0 answers
56 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 ...
1 vote
2 answers
313 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 ...
0 votes
0 answers
453 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 ...
1 vote
1 answer
915 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-...
16 votes
1 answer
4k 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 "...
0 votes
1 answer
111 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; ...
2 votes
1 answer
201 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 ...
2 votes
2 answers
473 views

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 ...
3 votes
0 answers
71 views

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 ...
2 votes
0 answers
220 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 ...
3 votes
1 answer
472 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 ...
1 vote
2 answers
750 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....
3 votes
1 answer
485 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 ...
5 votes
1 answer
243 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 ...
3 votes
0 answers
239 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 ...
2 votes
1 answer
336 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 ...
5 votes
1 answer
2k views

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. ...
1 vote
1 answer
959 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: $$...
1 vote
0 answers
67 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 ...
2 votes
0 answers
104 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 ...
1 vote
1 answer
851 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 votes
0 answers
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 ...
3 votes
3 answers
98 views

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&...
5 votes
1 answer
3k views

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 ...
2 votes
1 answer
400 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?
6 votes
2 answers
5k views

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: ...
4 votes
1 answer
904 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 ...
6 votes
1 answer
520 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 votes
1 answer
321 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 ...