# All Questions

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471 views

### Change particular color in an image

Suppose i have a image and I want to convert the portion of image that is red to blue(or any other color). One way to do this is extract red part of image using HSV or other color values and convert ...
29 views

### Why does the G1 term have a 2 in the numerator in Walter's formula, but not in Heitz's generalized formula?

In Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs, Eric Heitz derives the Separable Masking and Shadowing function as (P.83-84): In the mentioned Microfacet Models for ...
220 views

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

I'm interested in virtual reality, but according to some sources, less than 1% of computers in use today have the necessary performance to run modern VR games, granted many of them are not intended ...
447 views

### Ray-tracing the Cornell Box results in really inconsistent image

So I have a vector of glm::vec3 containing the triangles for the classic Cornell Box called triangles. The Draw method casts a ray for each pixel on the screen and ...
591 views

### How to compensate low amount of rays reaching the light in a Path Tracer

I am trying to implement for research purposes a path tracer, but so far but results are not so good and I will explain you why. The general idea before getting to the code: I am working on paths ...
263 views

### Collision detection methods for 2D and 3D environments [closed]

I found many sites, books and articles, all about especifics algorithms, I listed some of them (like bounding boxes, bounding spheres, octrees and KD-tree), but any of these founds lists every ...
5k views

### Is Russian Roulette really the answer?

I have seen that in some implementations of Path Tracing, an approach called Russian Roulette is used to cull some of the paths and share their contribution among the other paths. I understand that ...
4k views

### How to load a model in .json in three.js

I need to load a model "somemodel.json" into my "movie.js".Can someone tell me where i am going wrong.I followed the steps given here. index.html ...
1k views

### How could I use bent normal map

This might be a general question but I have some difficulties about understanding baked bent normal maps and how to use it inside a shader in Unity. From what I understand, bent normals are ...
505 views

### Could we dispense the near clipping plane?

Would it be, at least theoretically, possible to render without a near clipping plane? Could raytracing ignore this perchance? Quite many budding 3d artists have a WTF moment the first time they ...
117 views

### inside and outside region identification from 2D contour

A 3D model is sliced against a plane and the resulting 2D contour is projected onto the plane. I am looking for an efficient algorithm to identify the inside and outside region of the contour. ...
192 views

### Unlit objects in deferred rendering

What is the best way to draw unlit objects with deferred? Like skybox, particles or just glowing objects? I thought about mask in alpha channel, check it in light pass and just set diffuse color but ...
6k views

### What is an index buffer and how is it related to vertex buffers?

I have a vertex buffer like this: 0.0, 0.0, 1.0, 0.0, 0.0, 0.6, 1.0, 0.6, 0.5, 1.0 I have the following index buffer: ...
43 views

### Trouble using java connectivity and data transmition on libgdx [closed]

Hello everybody i have a trouble making datatransmition with mine program just to give the idea im trying to move this blocks when i move mine cars Here I leave the encoding of mine server/client ...
1k views

### Computing camera front direction from Euler angles

I am new to OpenGL and Computer Graphics in general. Lately I was learning how to model a camera, specifically how to model the rotation of camera. I was introduced to Euler angles for this purpose. ...
757 views

### How to generate OSX Flurry screensaver

I want to generate video similar to OSX Flurry screensaver (screenshot, video), but I have no idea how it is made. Does anyone here has an idea about how it's made, its algorithm and method?
5k views

### How to properly combine the diffuse and specular terms?

As far as I understand, in a BRDF the Fresnel term is telling us the probability for a photon to be reflected or refracted when it hits a surface. The reflected photons will contribute to the ...
206 views

### Sine-based Tiled Procedural Bump

I am trying to implement this formula to generate bump but I am facing some issue. The result doesn't look the same it's much darker. Here is my result (without same parameters) but it is much darker ...
548 views

### Path tracer not rendering shadows

I am trying to implement for research purposes a gradient-domain path tracer. In order to achieve this step I first need a working Path tracer. I have been creating one so far but results are wrong ...
561 views

### Can Frameless rendering reduce latency? And, can FPGA do 3D rendering instead of GPU?

In virtual reality, the motion-to-photon time is very important. Oculus says it has to be less than 20ms. Maybe 10~15ms is better. Some people try to introduce Frameless rendering technology into VR. ...
1k views

### Cloud based VR would be the future?

According to the following assumptions, I think Cloud based VR would be the future: 1) Real world scene rendering needs ray tracing or other complex computing graphics technologies. It needs a lot of ...
148 views

### Can V-Sync avoid tearing? I think it can't. Am I wrong?

1) Update the front buffer will cause screen tearing, every one knows it. 2) But V-Sync, I think it still get the same issue. Why I get this idea? 2.1) When GPU flips to the back buffer, current ...
93 views

### Why does the integral of NDF over a solid angle equals the area where micronormals belong to that angle?

In Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs, Section 2.2, Mr Eric Heitz defines the distribution of normals as: And then, he goes on with the following assertion: I ...
738 views

### How are we supposed to fix brightness with square roots?

I recently watched this video that talked from a physics perspective how most of the ways we deal with color on the computer is incorrect because brightness is on a logarithmic not linear scale. ...
93 views

### Converting from 360 degree vr to rectangular

What I am interested in doing is taking a 360 degree stereo video (Oculus Rift etc), and a description of how the viewing direction changes with time (rather than reading from gyroscopes) and then ...
217 views

### Coordinate system transformation in motion capture files

I am trying to align two motion capture files from different sources. The motion capture file consist of a skeleton specified as a hierarchy of joints. Each joint i.e. "shoulder" has three pieces of ...
200 views

### Human Readable/Writable 3D Representation Formats/Languages?

My goal is to create 3D meshes without the use of a 3D editor. So I want to know what representation languages and formats there are that are designed for this or otherwise that would be good for ...
270 views

### Gpu derivatives. How it's done across 2x2 boundary?

This question bothers me since the first time I got to know about derivatives in pixel shader. Suppose we have a 2d texture: 5 10 20 30 6 11 50 100 If I ...
64 views

### In what order to apply lighting and translucency?

I'm making a game that is supposed to like like a early 90s 3D game, so i'm rendering in software on an 8-bit indexed bitmap, using lookup tables for translucency and lighting. Now I have to draw a ...
840 views

### Which interpolation algorithm does MS Paint on Windows 7 use for image rescaling?

I was about to scale this image down to 64x64 pixels: The result I got on MS Paint on Windows 7 was surprisingly good (i.e. crisp edges): , whereas scaling it with GIMP resulted in for cubic and ...
126 views

### Strange behaviour of glDisableVertexAttribArray() on devices

In my graphics engine, based on OpenGL ES 2.0 I am using standardized name for shader attributes like it is done in libGDX (such as a_position, a_normal, etc.). When 'activating' my vertex buffer for ...
473 views

### phong equation of illumination specular component

I'm stuck on this question asking me to calculate the intensity of a pixel using Ray Tracing. It gives values such as $I_i$ but doesn't give any coordinates. I know for the diffuse component, \$...
3k views

### What are the current open problems in Computer Graphics?

I did a quick investigation about the topic but there doesn't seem a decent resource to find related problems without digging into latest CG papers (unlike CS problems you can easily find a Wikipedia ...
4k views

### Why do we have graphics frameworks like OpenGL and DirectX, when games could just draw pixels directly?

Games and other graphically intensive applications use frameworks like OpenGL and DirectX. Also they require features like pixel shader and DX12. But why would we need all these frameworks and GPU ...
114 views

### Generate complex (non-convex) polyhedron UV mapping

I need to find an approach to the problem of generating texture maps for non-convex polyhedrons without using a design tool like Maya. Specifically, I am mapping simulation results data onto a 3D ...
509 views

### Which 3D algorithms does Windows 10's “3D Builder” application use?

Windows 10 ships with "3D Builder", a Universal App that contains utility functions to prepare STL, OBJ, 3DS, and other files that represent geometries for 3D printing. The utility looks like this: ...
743 views

### How to convert Non-Axis Aligned Bounding Boxes to AABB

I am trying to write a ray tracer to render boxes that are arbitrarily rotated, i.e. not necessarily axis aligned. While I am reasonably comfortable ray tracing axis-aligned bounding boxes (AABB), I ...
707 views

### OpenGL C++ Camera Rotation Problem

Currently for a university assignment I have been given a 3D rendering engine, capable of rendering a 3D world. One task is to create a first person camera for it (I know with OpenGL you don't have a ...
557 views

### Maximum number of vertices after clipping a triangle against an AABB

I clip a 3D triangle against a 3D Axis-Aligned Bounding Box (AABB) to obtain the largest planar polygon of the triangle contained in the AABB. My clipping algorithm is a (slightly modified) version of ...
3k views

### How is VR different from a monitor

Apparently Macintosh computers cannot handle the Oculus Rift, because of their 'inferior' graphics cards. But should VR not just be like an external monitor? And concerning computer graphics, how are ...
78 views

### Model Separation - Several models reside in a single .stl file

I have an .STL file (ascii and binary format) that contains several different CAD models. How can I read the file and create separate .stl files for each of the single different models. Even some ...
707 views

### Spectral path tracing - image color/brightness incorrect

I implemented a spectral path tracing using physically base BRDF models such as Oren-Nayar,Specular Reflection and Transmission, Lambertian. All calculation in the path tracer uses standard illuminant ...
136 views

### maximal convex patching in Computer graphics

Given a 3D object in Computer graphics, whose surface is represented as a 3D triangular mesh (mesh of 3D triangle objects), I need to find the maximum continual Convex patches on the surface of the ...
96 views

### Can I run polygon insetting on the surface of a mesh?

I have a set of closed loops on the surface of a non-self-intersecting triangle mesh, and I need to create inset versions of them on the surface of the mesh. In other words, I want to generate a ...
4k views

I know how shadow mapping works but I am not getting the cause of shadow acne! Can anyone tell me cause of shadow acne in a simple way and how is it related to depth map resolution?
229 views

### Should not specular reflection on a rough surface be similar to diffuse reflection?

Different BRDFs are usually used to compute diffuse and specular reflection. Some of the most often used include for example the Lambert BRDF for diffuse reflection and the Cook-Torrance BRDF for ...
596 views

### Drawing to framebuffer texture - texture then split in half

I am doing exercises from the OpenGL SuperBible 6th Ed. I have managed to set up rendering into a framebuffer texture and then rendering from that texture to a cube. But for some reason, when the ...
158 views

### OpenSCAD Hull/Minkowski function by hand?

I am trying to model an organic object using OpenSCAD. However this will need to be ported over to older software. This restricts the primitives I can use (only cone, cylinder, torus, sphere and cubes)...