22 votes
Accepted

How are mipmap levels computed in Metal?

Mip selection is pretty well standardized across devices today—with the exception of some of the nitty-gritty details of anisotropic filtering, which is still up to the individual GPU manufacturers to ...
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  • 23.6k
15 votes
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Why use a tent filter in path tracing?

The theoretical ideal antialiasing filter for discretely sampled data is a sinc filter, because it perfectly removes all frequencies higher than the Nyquist frequency, while leaving alone all the ...
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12 votes
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Anti-aliasing / Filtering in Ray Tracing

There is a great paper from 2006 on this topic, Filter Importance Sampling. They propose your method 2, study the properties, and come out generally in favor of it. They claim that this method gives ...
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11 votes
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Help me grasp Anisotropic Filtering (AF)

To understand the nature of anisotropic filtering, you need to have a firm understanding of what texture mapping really means. The term "texture mapping" means to assign positions on an object to ...
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  • 8,101
7 votes
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Path tracer - multi layered materials and importance sampling

Wenzel Jakob et al presented a framework for layered Materials at SIGGRAPH 2014. Section 6.2 explains importance sampling. If you prefer code over equations, the method is implemented in the Mitsuba ...
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4 votes
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Ray tracing - partial derivatives for texture lookup

Yes, ray differentials are the way to go. The Paper by Igehy introduces them for the use case of filtered texture lookups. When generating the primary rays, you initialise the differentials to reflect ...
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4 votes
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Pixel dispersion (dissolving) algorithms

A very simple low memory approach If you really want to use as little memory as possible, it can be done with not much more memory than that required to store a single image (the first frame) ...
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  • 5,882
4 votes

What does filter mean in glint rendering and texture mapping?

Filtering refers to image processing operations that generate a new image by applying a filter kernel to an existing image. This is used for many purposes, but one of the most common is to resample ...
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4 votes
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Texture units parameters in OpenGL

Your understanding of the behavior of texture units and state is confused. That's to be expected: OpenGL's pre-DSA API is not making it easy to understand this. As far as core profile OpenGL is ...
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  • 8,101
4 votes
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Kaiser windowed sinc filter for mip mapping

I was curious so I tried it. I used the Kaiser Window from Wikipedia: $\frac{I_0\left(\alpha\sqrt{1-x^2}\right)}{I_0\left(\alpha\right)}$ This page has a slightly different formulation using $\pi\...
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  • 1,575
3 votes
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Unexpected results from Mitchell-Netravali

Mitchell–Netravali has negative lobes, which are generally not recommended for small sample counts from what I understand; you tend to end up with both the positive and negative areas undersampled. ...
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3 votes
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Plotting pbrt-v3 Gaussian filter

You probably want to set sigma to be a fraction of the radius, rather than a fixed value. Sigma controls the actual shape of the filter, while radius just controls how far out the filter gets cut off (...
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3 votes

Why use a tent filter in path tracing?

I just looked at Wikipedia articles about Bilinear interpolation. A tent filter is a kind of Bilinear interpolation. A Bilinear interpolation interpolates on 2 dimensions. It first linearly ...
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  • 1,565
3 votes

Help me grasp Anisotropic Filtering (AF)

A few points that you probably already know, but that I just want to put out there for others reading this. Filtering in this case refers to low-pass filtering like you might get from a Gaussian Blur ...
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  • 3,331
2 votes

Pixel dispersion (dissolving) algorithms

You could do this entirely within an OpenGL/WebGL fragment shader: Attach the image you wish to emerge as a texture/sampler2D. Attach uniforms for the current time, as well as the time you want the ...
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  • 331
2 votes

Does film filter introduce bias in path tracing?

This is an answer to your comment rather than the title of your question. It can be considered as a partial answer. The bias in path tracers are introduced by the estimators. For example, think of the ...
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  • 441
2 votes
Accepted

How does the GPU know whether to magnify/minify?

Minification vs magnification is an extension of mipmap selection. When you calculate the desired mip level, it can come out to be less than 0 (or in general, less than the sampler's configured ...
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1 vote

What is a common approach to smooth structures in textures?

I don't have enough rep to add a comment so... You could use a post process based anti-aliasing technique like FXAA or SMAA. Also, if performance is not a priority, you could go for SSAA. Another ...
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  • 110
1 vote

Suggested image preprocessing before applying threshold

In your case, I don't think a pre-processing is necessary. You may find the Hough transform useful in your case. Since your image is big, it can be difficult to have a straight line due to the noise ...
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