# All Questions

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506 views

### What if we don't mention Modelview and projection matrix?

So I've been learning opengl for some weeks now and managed to understand all the viewing pipelines. As far my understanding goes we need to bring the object to world space and then the world space to ...
153 views

Context As I was trying to learn more about Vulkan, I learned that certain fixed-function steps could be implemented with shader code from this video (at around the spot where he talks about the ...
203 views

### The Process of Spherical Harmonics

I have read about spherical harmonics from Here about the usage of SH for generating Irradiance Environment Maps and how it can make the process of generating EM faster than the regular operations. ...
218 views

### Real time image based lighting for arbitrary BRDFs coordinate alignment

I was trying to understand how real-time illumination happens with image-based lighting. I understood that importance of representing the Environment Map and BRDF in spherical harmonics. Because ...
202 views

### OpenGL ES Frag Shader - Branching

Working on optimizing a fragment shader which is slowing down my OpenGL ES 2.0 shader based game. This is used with a shadow buffer to determine if the fragment/pixel is inside a shadow volume. The ...
7k views

### Programmatically generating vertex normals

I'm working with Kinect face api, it provides an array of vertices and indices for triangles which is to be rendered to make the face image. The no of vertices and their order in array as well as the ...
109 views

### Alternatives to Clipping in avoiding display problem

I know in computer graphic, we can set a world window in world coordinate system, and then mapping it to viewport which is the display window. Things that are not in the world window should not be ...
667 views

### Transforming fragment-to-camera to tangent space for parallax occlusion mapping

I'm trying to implement POM using this tutorial. As stated, I need to transform fragment-to-camera to tangent space and then pass it to a function. tangent space is computed using Assimp. Well I ...
403 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 ...
177 views

### Encode two R11G11B10F buffers into one using Y'CbCr?

We are trying to optimize Lighting in fillrate. Integrated graphics chips are very slow in memory access. There are two Light Buffers: one for Diffuse and one for Specular. Both use format R11G11B10F....
117 views

### How can I implement a complex sinusoidal function?

The following is the 2d complex sinusoidal function, $u_0$ and $v_0$ represent Fundamental Frequencies in $X$ and $Y$ directions respectively. How can I represent $j$ (imaginary number)? Edit: ...
182 views

### Error with tube lighting

I have recently been working on area lights for a small open source game engine called Urho3D but have run into an issues when rendering tube lights where the lights look the same as sphere lights ...
693 views

### What is the fundamental reasoning for anti aliasing using multiple random samples within a pixel?

In graphics, it's common to take multiple samples within the bounds of a pixel and combine them together (most commonly just doing an average) for a final sample pixel color. This has the effect of ...
483 views

### Do we use 3x3 matrices in computer graphics?

I've been doing some side-research on computer graphics as a hobby and came across this article on quaternions: http://www.opengl-tutorial.org/assets/faq_quaternions/index.html#Q2 In the first ...
585 views

### Rotate a cylinder from XY plane to given points

I am given geometry of a cylinder which lies on the XY plane with 1 unit radius. And given coordinates of 2 points in 3D I need to move the cylinder so that it connects the two points. What I tried ...
989 views

### Proper way to handle diffuse + refraction + reflection rays in path tracing?

Let's say we are path tracing and that there is an object which has some amount of diffuse reflection, and some amount of specular reflection. What is the best or correct way to handle that in the ...
2k views

### Background behind 3D model

I have object loader, which i want to have background. I tried to put jpg image like texture to my application. I tried to make that with FreeImage library, but the image didn't show. Also i tried ...
278 views

### Is this Russian roulette code correct?

I'm using www.scratchapixel.com among other resources to help me learn how to implement a renderer. I am looking at the following code from this page where a packet of photons moving through a ...
3k views

688 views

### Solid angle and surface area values in (photometric) raytracing

So, I started writing my second raytracer - this time focusing on photometric rendering that uses IES lights and standard photometric units. I've got the basic raytracing up and running (using pure ...
328 views

### OpenTK - Vertex attribute layout issue

I use C# and OpenTK as my OpenGL implementation. My Vertex layout consists of 6 Doubles and one Float: ...
286 views

### Where is the best place for Tangent-bitangent calculation, in shader or in C/CPP code?

I have two methods of calculating tangent and cotengent (needed for normalMap lighting calculation). The one is doing it from CPP code (with assimp library for example) The second is doing it ...
536 views

### OpenGL: Purpose of transform matrix in Vertex shader where transform*vertex

I'm trying to understand OpenGL by using Processing OpenGL ES. If I have an example Cube to render. I've read that a vertex shader will be run once for each Vertex. The fragment shader will be run (...
76 views

### Use big frame buffer to control a small display

I am really new in computer graphic area. Suppose I have 1024*1024 frame buffer, and I want to use it to control a 512*512 display. What shall I do? In my opinion, I will only read the information in ...
92 views

### Unfolding a 3D point to a Cartesian plane

I am writing a texture splatting pixel shader for meshes (not terrain) whereby I find a UV position from a raycast, which I convert to a local position, and then calculate a bounding box around that ...
224 views

### Creating Sparks using Code

I'm new to this area and have less knowledge. I want to create some graphics like sparks and lightning by writing some code, using my own physics. I don't want to use some engine, However I can use ...
83 views

### Image cleaning - removing all regular shapes ( circles, squares, text, icons etc. )

I'd like an automatic method to clean images. I've been looking at the GIMP, and its command line (cli) interface, in scheme / lisp. It looks very promising, but I'm a complete novice, so I'd be ...
174 views

### selectively setting stencil value based on vertex property in vertex shader

Just like the question says. Is it possible to selectively set the value of the stencil buffer based on a property of a vertex, like the value of its normal, during its vertex processing phase? ...
512 views

### Only show opaque objects behind transparent objects

I would like to make certain objects in my scene transparent, but only the parts visible to the camera when opaque. Currently, when I make objects transparent, I can see other transparent objects ...
1k views

### Is it expected that a naive path tracer takes many, many samples to converge?

I have a naive diffuse/emissive material path tracer implementation (pinhole camera) and am seeing it take a very large number of samples per pixel to converge - like probably in the millions - and ...
83 views

### What is a good algorithm, and framework, to calculate centres of gravity or mass (cog)?

I'd like to take an photograph, subdivide it into a tesselation, either of squares, or (ideally), hexagons, and then find the centre of gravity (or, if you prefer, centre of mass) of each cell of the ...
4k views

### Confusion between usages of linear RGB and sRGB

Suppose you have generated an image using linear values for RGB channels. E.g. you linearly interpolated it when doing blending, etc.. When you're going to present this on the screen, should the ...
319 views

### How to correctly render visible spectrum with uniform intensity?

I'm trying to get the correct representation of visible spectrum to render on the screen. My current progress is with using CIE 1931 standard observer color matching functions analytically ...
49 views

### Photo-realism blind experiment [closed]

I need a lot of real time rendered images and real images where it's recorded which one is which to prove either way whether existing gaming computers have the hardware to be photo-realistic to ...
2k views

I use Phong shading as my lighting model. Nevertheless, the specular shading produces gradients in the light cone: Hopefully you can see the gradient starting from the lower left corner expanding ...
232 views

### Frustum aligned volume integration - aliasing issue - temporal reprojection

Raw volume raymarching especially aligned with frustum seem to produce a lot of aliasing/banding on edges of shadow map. Especially when fragment pos is far because step length is then getting bigger. ...
291 views

### Bug: Overly Sharp Highlights in PBR

I'm still working on my BRDF equations. Theoretically, all equations are correct, but the hilights are super sharp. I'm not sure if this is a result of me not using Image-Based Lighting (I currently ...
7k views

### Physically based shading - ambient/indirect lighting

I implemented a physically based path tracer after studying PBRT by M. Pharr and G. Humphreys. Now I'm trying to apply physically based rendering to real time graphics using OpenGL ES (in an iPhone ...
131 views

### Where should I project a polygon corner when it is behind me?

I am creating a simple 3D engine as a learning project to get the hang on spherical trigonometry. I am using the following approach. 1. A model consists of a lot of triangular faces. 2. Each triangle ...
2k views

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

For a while I have been doing some research on the topic of Physically Based Rendering. One reflection model that is mentioned over and over is the Cook-Torrance / Torrance-Sparrow model. It seems ...
218 views

I have been working on how the GPU does parellel processing, and branching. However I am not yet to the point where I know how to make this shader more efficent. Essentially I dont know enough about ...
1k views

### Screenspace Normals - Creation, Normal Maps, and Unpacking

I'm trying to condense my Deferred Rendering G-Buffer. So I have some questions about getting 2-component Screenspace Normals. I know Frostbite and Killzone (the only two AAA company's G-Buffers I ...
68 views

### What happens when GL_Depth is disabled

In my simulation I draw a bunch of rectangles with GL_TRIANGLE_STRIP inside of one draw call. What will happen if I turn off GL_DEPTH_SORT? If all of the rectangles were stacked on top of themselves ...
239 views

### How to get unique nearest neighbour?

There's already something called K-nearest neighbour algorithm with gives nearest neighbour to points. But what I want is unique neighbour which is not shared by any other neighbour. I've implemented ...
965 views

### What Are The Default Values of glReadBuffer/glDrawBuffer(s) for an FBO?

glReadBuffer(...)/glDrawBuffer(...)/glDrawBuffers(...) access part of a framebuffer's state. ...
615 views

### Animating a smooth linear transformation

After watching this video on matrices, I tried to make a simple animation of 2D linear transformations. Starting with a set of 2D points in a grid, I applied a 2x2 matrix to each point and obtained a ...
189 views

### Weird rendering in rectangle mesh shader AKA Why has my basic shader become a modern art generator?

I am trying to translate an old (2013) bit of code from Apple from objective C to Swift with some modifications I need for my simulation. The code I am translating can be found here To make ...
1k views

### Algorithm for adjusting the speed of a progress bar animation

I am trying to figure out an algorithm for handling an otherwise simple animation. I have a progress bar that "ticks down" from a user specified amount of time to zero. I wanted a smooth animation, so ...
A 2D vector can be rotated by an angle $\theta$ using the rotation matrix: \begin{bmatrix} \cos(\theta) & -\sin(\theta) \\ \sin(\theta) & \cos(\theta) \end{bmatrix} Or, it can be rotated by ...