# All Questions

2,149 questions
412 views

### Convolution of Hemispherical Harmonics

Spherical Harmonics (SH) are a way to represent low-frequency spherical functions with only a handful of coefficients. They have some nice mathematical properties, e.g. a convolution with a kernel ...
723 views

### GLUT OpenGL - Drawing Shapes using only GL_POINTS

I'm working on an assignment and I need to draw using only GL_POINTS. I realize this is an expensive approach but it's for the homework, so no GL_TRIANGLES / GL_POLYGON / GL_LINES etc. First, I'm ...
4k views

### What algorithm(s) are behind Google Street View's 3d mapping mode?

I recently noticed that in some locations you could switch to a 3d mapping mode in Google Street View. Which algorithm(s) did they use to generate the 3d models of the streets? I assume it was more ...
174 views

### How could I check the correctness of my result of fluid simulation?

I wrote a particle based fluid simulating program. It's hard to tell if I get the right result. The visualized result seems reasonable, but some part of it looks weird. I don't know wether it's a ...
2k views

### How does hardware texture compression work?

That it compresses the data compared to the pixel array is obvious. But what makes it different from from normal compression (like png, jpeg)?
143 views

### How can I get a spherical visibility mask map for a point on a concave surface?

I encountered this problem doing my project. Suppose there is a 3D mesh model, e.g. a human face, I need the 3D visibility map at each of the vertices of this model. By the "3D visibility map", I mean ...
2k views

### What is the accepted method of converting shininess to roughness, and vice versa?

Most modern renderers use physically-based materials and their models are often parameterized over roughness. Since this wasn't always the case with renderers, conventional assets often don't have a ...
3k views

### How physically-based is the diffuse and specular distinction?

The classical way of shading surfaces in real-time computer graphics is a combination of a (Lambertian) diffuse term and a specular term, most likely Phong or Blinn-Phong. Now with the trend going ...
2k views

### Why do most photorealistic renderers have similar material test scenes?

I notice that most photorealistic renderers have very similar material test scenes. Here are a few examples: Blender Mitsuba Vray My question is: why is this specific model / style chosen to test ...
5k views

### Why is the transposed inverse of the model view matrix used to transform the normal vectors?

When rendering 3D scenes with transformations applied to the objects, normals have to be transformed with the transposed inverse of the model view matrix. So, with a normal $n$, modelViewMatrix $M$, ...
715 views

### Is there some kind of Bresenham algorithm or equivalent for scanline rendering a rotated ellipse?

Back in the day when you often had to write your own low level rendering algorithms we all used to learn the Bresenham algorithms for lines and circles. It was almost trivially easy to extend the ...
337 views

### How to ignore rain or smaller objects movements in motion detection? [closed]

I first read Alan's answer about video noise removal which lead me to this question. I found later some algorithms ideas which capture motion in a similar way (frame comparison, as Alan described). ...
7k views

### Does a sphere projected into 2D space always result in an ellipse?

My intuition has always been that when any sphere is projected into 2D space that the result will always mathematically be an ellipse (or a circle in degenerate cases). In the past when I was ...
259 views

### Algorithms for scan converting b-spline and nurbs

In all computer graphics books there are algorithms for scan converting simple primitives like lines, circles, ellipse,... I can't find algorithms for more advanced curves like bezier curves, b-...
4k views

### How to make a 3D model for Unity 5 [closed]

I'm using Unity 5 to make a small game (I'm a beginner) and I want to make a 3D model of a character. I'm not sure what software there is to do this and if there is some, I would like it to be ...
232 views

### Does UV-mapping generate for some points of the 3D model several points in the 2D projection?

Assume my 3D model is a pyramid with a rectangular base and I numerate four corners of the base with 1, 2, 3, 4 and give 5 to the top point. If I project this pyramid into a 2D star-shaped object, ...
89 views

### Two-dimensional bounded area defined parametrically

How do I go about defining this area without using a piecewise function? I think it has something to do with Bilinear Surfaces but I'm not sure how to get started.
2k views

### What is the difference between various space-filling curves?

Space-filling curves are important in many graphics applications because they help expose spatial locality. We often hear about different algorithms using Z-curves, Morton codes, Hilbert curves, etc. ...
209 views

### Is it possible to modify a console game graphics (Xbox 360)?

There's a thing called ENB for PC which works by modifying render functions calls of the games and applying additional effects. I wonder if there is a similar way for console games.
1k views

### How many Direct/Compute/Copy Queues are meaningful?

DirectX 12 exposes command queues for either graphics (called "Direct"), compute or copy tasks. In terms of provided functionality, each one is a super-set of the following one. The specification ...
324 views

### Texture glitch when using simple pixel shader

I have an issue with rendering my textures in Silverlight. When I look at it from above everything looks fine: But if I only change angle of watching it it looks terrible: I am using very simple ...
360 views

### Problem with definition of BSDF and radiance

When I was reading theory behind physical based rendering I noticed that definition of BSDF and radiance has some problems. For example BSDF of purely specular surfaces is zero almost everywhere and ...
235 views

### An introduction to Lane-Riesenfeld algorithms [closed]

I am looking for a good introduction to Lane-Riesenfeld algorithms, which are a family of subdivision methods for generating uniform B-splines. Any suggestions? Note. This is a copy of the question I ...
3k views

### Physically based rendering and ray tracing

I've got a lot of confusion and I need to clarify some terminology and put together the knowledge. If I say that an engine is a ray tracer (so it uses the ray tracing algorithm to render the scene), ...
3k views

### Why do T-junctions in meshes result in cracks?

I have heard from many sources that having T-junctions in 3D meshes is a bad idea because it could result in cracks during rendering. Can someone explain why that happens, and what one can do to avoid ...
1k views

### What is the practical difference between 3D Graphics Engine, 3D Game Engine, 3D …?

What is the practical difference between 3D Graphics Engine (OGRE), 3D Game Engine (Quake), 3D Software Rendering Engine, 3D Graphics API (OpenGL/DirectX)? Is OpenGL/DirectX a 3D Graphics API or a 3D ...
2k views

### What formula or algorithm can I use to draw a 3D Sphere without using OpenGL? [closed]

I know that there are 3 techniques to draw 3D objects: (1) Wireframe Modeling and rendering (2) Additive Modeling (3) Subtractive Modeling Am I correct? What formula or algorithm can I use to draw a ...
245 views

### How many 3D textures does OpenGL support

I'm making a voxel engine in OpenGL and wondering how many 3D textures I can have at once. They are fairly large (256x256x256 in GL_R32UI format). I want it to be able to run on any graphics card ...
265 views

### Legendre Polynomial equation in Spherical Harmonics

I recently started to read about spherical harmonics. I have a question about this spherical harmonics basis function equation which is mentioned in this StupidSH article: What are those lm() and Re()...
2k views

### How does mip-mapping work with non-power-of-2 textures?

I have heard that recent GPUs all support non-power-of-2 textures and all features just work. However, I don't understand how mip-mapping would work in such a scenario. Can someone explain?
296 views

### Can we use anisotropic filtering on 3D textures?

Do modern GPUs support anisotropic filtering for 3D textures? If yes, how can one use it? The OpenGL spec doesn't seem to be very precise on this. From this link: ...
3k views

### What is the state of art in geometric LOD in games?

How do modern games do geometry level-of-detail for object meshes like characters, terrain, and foliage? There are two parts to my question: What does the asset pipeline look like? Do artists make a ...
196 views

### How does the view-independence of radiosity increase the calculations involved?

In the style of trichoplax' question, I want to talk about yet another Wikipedia article: Radiosity (computer graphics). The article states: Radiosity is viewpoint independent, which increases the ...
3k views

### How is anisotropic filtering typically implemented in modern GPUs?

Anisotropic filtering "retains the sharpness of a texture normally lost by MIP map texture's attempts to avoid aliasing". The Wikipedia article gives hints about how it can be implemented ("probe the ...
125 views

### Is colorized subpixel rendering possible?

Subpixel rendering is used most commonly to anti alias fonts. It works by leveraging the physical layout of the color components of a display to give geometry details to an image that are smaller than ...
844 views

### Subpixel Rendering for a Ray Tracer

In font rendering, it is common to use subpixel rendering. The basic idea here is to break the pixel into its RGB components and then compute a value for each separately. Since each component is ...
1k views

### Ray Tracing with Cones: coverage, overlapping and abutting triangles

In his classic paper Ray Tracing with Cones, John Amanatides describes a variation on classical ray tracing. By extending the concept of a ray by an aperture angle, making it a cone, aliasing effects (...
1k views

### Are there any gltf example datasets available? [closed]

I'm currently researching my options on effeciently exchanging data for a webgl application. I understand the gltf format is still being drafted but I need some example data to understand whether this ...
148 views

### Software to compose separate models into an articulated model?

I've inherited a system which animates a humanoid avatar by loading various models and manually calculating transformations for each one. I'm in the process of porting part of this system to Three.js, ...
298 views

### Changing image so it would look like through colorful glasses

I am currently working on some simple pixel shader in HLSL. I send to shader texture and I want to make it more colorful (something like in the picture below). In the picture 1 there is original ...
496 views

### How to produce simple 2D illustrations to accompany geometry answers?

In my answer about Affine Transformations I made some little illustrations to help the explanation. How do you make an upload-able PNG quickly which expresses a geometrical or mathematical idea? ...
1k views

### Synchronizing successive OpenGL Compute Shader invocations

I have a couple of compute shaders that need to be executed in a certain order and whose outputs depend on previous inputs. Ideally, I'll never need to copy a buffer client-side and do all of my work ...
271 views

### How to denoise video?

Video noise is random and not correlated in time. I assume, the best method is using wavelet denoise in this case, right? If yes, how is wavelet denoise implemented for video? Is there something to ...
351 views

### What is the meaning of words 'stochastic', 'temporal' in computer graphics?

Last time I see a lot of papers which operates on this words, i.e. stochastic AA, temporal coherence etc. What does that means? Can you provide examples with explanations in plain English?
5k views

### What are Affine Transformations?

What are Affine Tranformations? Do they apply just to points or to other shapes as well? What does it mean that they can be "composed"?
1k views

### What is occlusion?

Occlusion "is the effect of one object in a 3-D space blocking another object from view." With this definiton in mind I cannot understand sentences like: The interior of a tube is typically more ...
301 views

### What is ambient occlusion?

Ambient occlusion "is a shading and rendering technique used to calculate how exposed each point in a scene is to ambient lighting. Ambient lighting is regarding to What is ambient lighting?: ... ...
8k views

### Shading: Phong vs Gouraud vs Flat

How do they work and what are the differences between them? In what scenario should you use which one?