20 votes

When is a compute shader more efficient than a pixel shader for image filtering?

John has already written a great answer so consider this answer an extension of his. I'm currently working a lot with compute shaders for different algorithms. In general, I've found that compute ...
bernie's user avatar
  • 830
20 votes
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Cause of shadow acne

Image 1: A bad case of shadow acne. (Synthetic and a bit exaggerated) Shadow acne is caused by the discrete nature of the shadow map. A shadow map is composed of samples, a surface is continuous. ...
joojaa's user avatar
  • 8,417
15 votes

Rendering equation - why unsolvable directly?

I'm sadly not able to add a comment to the answer above (not enough reputation), so I will do it like this. I'd like to point out that what Dragonseel describes is simply an integral equation (...
Vanbus's user avatar
  • 304
13 votes

Rendering equation - why unsolvable directly?

The rendering equation is as follows: Now, the integral is over the sphere around the point $x$. You integrate over some attenuated light, incoming from every direction. But how much light comes in? ...
Dragonseel's user avatar
  • 1,810
13 votes

Correct Specular Term of the Cook-Torrance / Torrance-Sparrow Model

I would trust Pharr and Humphreys on this. Equation 2 also agrees with the SIGGRAPH Physically Based Rendering course notes, as well as with equation 20 in the Walter et al paper that introduced the ...
Nathan Reed's user avatar
13 votes

How to achieve gimbal lock with Euler angles?

A gimbal is a pivoted support that allows you to rotate around one axis. Now it so happens that Euler rotations* work like a set of 3 gimbals attached to each other,...
joojaa's user avatar
  • 8,417
13 votes
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For shader math, why should linear RGB keep the gamut of sRGB?

Talking about Linear RGB must be avoided because it does not tell you anything about the RGB colourspace intrinsics, i.e., Primaries, Whitepoint and Colour Component Transfer Functions. A few years ...
Kel Solaar's user avatar
12 votes
Accepted

What are the use cases for multiple render passes?

Instead of listing specific use cases, I will explain the technical limitations of a render pass structure which would prevent someone from putting all of their rendering within it. The use cases ...
Nicol Bolas's user avatar
  • 9,752
11 votes
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How to achieve gimbal lock with Euler angles?

Rotations in 3D are normally done with matrices. The xyz Euler angles can be converted to matrices so that it can be used in the rotation. That is where something called rotation order comes in. ...
bram0101's user avatar
  • 1,595
11 votes
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What are 'mesh clusters' / hierarchical cluster culling (with LOD?) / triangle cluster culling and how do they relate?

First, to preface: the reason it's hard to find details about these hierarchical cluster culling systems because they are a still emerging field, at the very cutting edge of real-time rendering ...
Nathan Reed's user avatar
10 votes

Cause of shadow acne

As an addition to the answer of joojaa: Using a bias to offset the shadow function does indeed solve the problem with shadow acne, but it can introduce an additional problem: Peter Panning As you see ...
Dragonseel's user avatar
  • 1,810
10 votes
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How does the rendering equation incorporate shadowing

Light that is blocked will mean that $L(p*, -w_i)$ under the integral is 0 plus how much light the blocking object itself reflects. In other words the shadowing is embedded in the incoming light ...
ratchet freak's user avatar
10 votes
Accepted

Perspective Correct Texture Mapping

You are on the right track but what you need to do is to calculate u/w and v/w, and also 1/w for each vertex, which you interpolate linearly in screen space in your rasterizer. Then for every pixel ...
JarkkoL's user avatar
  • 3,626
10 votes

Formula for the ambient light intensity of a scene?

Using an 'ambient light' term in your lighting calculations is an approximation of the indirect light reflected around the scene. Usually it's up to the artist to choose an appropriate value. There ...
RichieSams's user avatar
  • 3,732
9 votes
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Difference between rendering in OpenGL and 3D animation software

The main difference would be that with OpenGL in let's say a video game, you will have a process called rasterization which basically takes care of determining what part of the scene you see. It needs ...
xoryouyou's user avatar
  • 205
9 votes
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What methods/technologies to reduce required performance for virtual reality are there?

Avoid stereo when possible There was some research published recently measuring when users can or cannot tell whether the specular contribution, which is view point dependent, is different between ...
Julien Guertault's user avatar
9 votes
Accepted

What is the difference in overlay and framebuffer?

As you've understood, the framebuffer is an array in memory that holds all the pixels to display on the screen. On a desktop PC, it's probably special memory on the graphics card, but in a SoC with ...
Dan Hulme's user avatar
  • 6,770
8 votes
Accepted

Compensation for energy loss in single-scattering microfacet BSDF models

To my knowledge, there is no easy and analytic way of recovering the energy lost in single-scattering models. The previous techniques precompute the energy loss and reinject it in the BRDF as a ...
Eric Heitz's user avatar
8 votes

What kind of technology would be involved in the rendering of human nails?

I'm not aware of any rendering technology designed specially for fingernails. Just eyeballing it, I would suggest that a combination of subsurface scattering with a relatively smooth glossy specular ...
Nathan Reed's user avatar
8 votes
Accepted

Area Lights in Path Tracing

I'm going to provide the simple/naive/brute force answer to this question, which does work, and gives accurate results. There are better answers however, which make the rendering converge faster with ...
Alan Wolfe's user avatar
  • 7,791
7 votes

Albedo vs Diffuse

The Diffuse, specular and Reflection terms have lead to a lot of confusion because they have been commonly used to describe different lighting processes along the CG history and sometimes diverge from ...
Titou's user avatar
  • 71
7 votes

Difference between rendering in OpenGL and 3D animation software

You're comparing apples to oranges The game is like the view port in your modelling app. You can use the viewport for render and you will get same 60fps speeds. There is no reason why you can not get ...
joojaa's user avatar
  • 8,417
7 votes

What methods/technologies to reduce required performance for virtual reality are there?

Alex Vlachos from Valve has had two great GDC talks about this: the one from 2015 the one from 2016 Other than that (and what you have linked yourself), there isn't much left to do than to simply ...
IneQuation's user avatar
7 votes

What kind of technology would be involved in the rendering of human nails?

I don't know of any specific technology for rendering fingernails, but I agree that using subsurface scattering with some specular would be a good starting point. A couple of things I'd take into ...
Icetigris's user avatar
7 votes

Importance Sampling of Environment Maps

This is not a full answer, I would just like to share the knowledge I obtained by studying two of the papers mentioned in the question: Steerable Importance Sampling and Practical Product Importance ...
ivokabel's user avatar
  • 1,454
7 votes
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Role of PDF of Uniform Random Sampling in a path tracer

Firstly, as @trichoplax correctly pointed out, your randomPoint function calculates a point in a cube, then uses rejection sampling to return all points that are inside a unit sphere. In order to ...
RichieSams's user avatar
  • 3,732
7 votes
Accepted

What physical properties are “lacking” to keep this 3D scene from looking like a real photograph?

Few things, but usually this is what it takes to make the difference: 1- the material reflection at his head, he is bald, yet the diffuse texture shows color difference where the hair is, this means ...
Georges D's user avatar
  • 186
7 votes
Accepted

Do animation studios like Pixar, Dreamworks, and Disney use super-sampling?

Super-sampling for ray-tracing doesn't just mean rendering an area at higher resolution and then downscaling the finished image: in fact, this simplest super-sampling technique is really not effective ...
Dan Hulme's user avatar
  • 6,770
7 votes

Why do games only allow certain resolutions?

Note that in your Dark Souls example, all the resolutions listed are the exact same aspect ratio. So the question is, why doesn't it support arbitrary aspect ratios? The answer is that it costs ...
default's user avatar
  • 333

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