# All Questions

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### Transform a point into another point

I have the following problem: Give a matrix that will transform the point $(x,y,z)$ into the point $(\frac{2}{x+y}, \frac{5y + z}{2x + 2y}, 3)$. I have been reading my book to find a way to solve it ...
3k views

### Detect in-focus regions of an image

Is there any strategy to detect the region of an image that is sharp and in-focus, in order to separate the out-of-focus background? I've tried using edge detection methods but without any success. ...
466 views

### Moires patterns despite using mipmaps

I am working on Silverlight app. I am trying to render floor covered with tiles. Although I am using mip maps I am still getting awful Moire patterns, when trying to render big area. What I am doing ...
49 views

### Measure how long a rendered frame takes to arrive on a client from the cloud [closed]

Say I am running a game in the cloud and I am playing that game on my client (the game is being streamed from the cloud to the client), be it a laptop, phone or calculator. How can I work out how ...
854 views

### Actual vs Perceived Brightness of RGB Colour

In this video from about 1:15, it is stated that if you have an RGB value of (0.5,0.5,0.5) it is only 22% as bright as (1,1,1) rather than the expected 50% as bright. Does this mean that RGB is ...
163 views

### To what degree, if at all, can custom code be embedded in a PNG, GIF, or JPG?

Computer graphics files are in Windows rendered by components such as the Graphics Device Interface and Direct2D. Is it possible to create a graphic file that, besides displaying a graphic also ...
263 views

### Can raytracing be used to imitate the behavior of light to a higher degree?

Raytracing "sees" the pixel on the other side of the screen; but doesn't this mean the rays traced can be computationally reflected and refracted imitating the properties of actual light? It'd be ...
181 views

### Do the alignement and declaration order of uniforms matter?

In the section 6.4 Constant Buffers of the book Practical Rendering & Computation with Direct3D 11 (pages 325, 326) it is mentioned: By default, the HLSL compiler will attempt to align ...
143 views

### How to capture rendered frames from an application and stream over network

I'd like to know (if it is possible), how I would go about getting at the rendered frames from an application. For example, say I am using some 3D modelling tool (eg Blender, 3DS Max, Maya) and I ...
1k views

### What is the modern equivalent of display lists?

Display lists were an OpenGL feature that could, in theory, accelerate any part of the API by storing a group of commands for later use. In my understanding, this makes a lot of sense with regards to ...
2k views

### Does PBR incur a performance penalty by design?

I am wondering if the various PBR models used in modern game engines for real time are heavier in terms of computation, that more classic approaches to rendering. Worded differently, is PBR just a ...
183 views

### Help me find out what this texture mapping technique is called

I'm in the process of making a tool that requires rendered texture to follow the contours of a piece of clothing. An example would be this website https://knyttan.com/editor/jumper-editor/. The effect ...
63 views

### Can the uniform id be changed from run to run on the same machine?

I have a shader which has several uniform variables: uniform vec4 a; uniform vec4 b; uniform vec4 c; I'm getting these handles using ...
6k views

### How to Calculate Surface Normals for Generated Geometry

I have a class that generates a 3D shape based on inputs from the calling code. The inputs are things like length, depth, arc, etc. My code generates the geometry perfectly, however I am running into ...
185 views

### Realistic rendering: which processes of the human eye and brain do I need to consider?

Photorealistic rendering has the goal of rendering an image as a real camera would capture it. While this is already an ambitious goal, for certain scenarios you might want to take it further: render ...
571 views

### Fresnel reflectance of gold: red channel greater than 1?

I've been trying to understand some of the physical principles behind light and material interaction lately. In his talk Physics and Math of Shading, Naty Hoffman explains Fresnel reflectance and ...
207 views

### CUDA cuMemcpuHtoD vs cuMemcpy2D

Asking it here and not on SO as it seems to be appropriate question for CG. I am learning NVIDIA NVENC API.The SDK supplies a sampled called "NvEncoderCudaInterop" .There is a chunk of code which ...
724 views

### What are the best ways to start graphics programming? [closed]

[I got a warning that the question will be closed]. I have identified that CG is the place where all the advanced algorithms and computations are taking place. What is the best way to start from ...
852 views

### Fundamentally, how are 2D bitmaps rendered?

Suppose we have a 64-bit word-addressable computer and we want to program it to output a 5x7 character stored as a binary image bitmap (such as the one below) to a memory-mapped display. Since we ...
853 views

### Convert RGB, Hex or any other color format to “Standard Color” Programmatically

Forgive me in advance for my ignorance. Using the PHP function imagecolorat, I have a solution that presently delivers a set of the most dominant hex color codes available inside of an image. Is ...
130 views

### How to extract a BRDF from a shader [closed]

For normalization purposes, how to "extract" a BRDF function from an ad-hoc piece of pixel shading code ? If we have a shader function like: ...
23k views

### Why are Homogeneous Coordinates used in Computer Graphics?

Why are Homogeneous Coordinates used in Computer Graphics? What would be the problem if Homogeneous Coordinates were not used in matrix transformations?
497 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 ...
830 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 ...
182 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 ...
3k 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)?
160 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 ...
3k 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 ...
4k 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 ...
6k 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 $M$, ...
916 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 ...
405 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). ...
8k 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 ...
287 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 ...
250 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.
3k 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. ...
210 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.
2k 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 ...
349 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 ...
399 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 ...
282 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 ...
4k 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), ...
4k 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 ...
2k 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 ...