# All Questions

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### Is it possible to develop this image generator from randomly redrawn detected edges or am I going straight to the wall?

Aim I would want to procedurally generate totally new images from a set of thousands of images of a given category (simple landscapes for example). Deep-learning won't be used for this purpose. This ...
48 views

### In Game Engines, how much of the graphics pipeline is already written?

I'm trying to understand how much graphics programming actually needs to be done if you are using an engine like Unreal Engine to build and package a game. I understand some of this might have to do ...
26 views

### How to do a scanline fill with a self intersecting polygon?

I have a bezier curve and would like to draw it's stroke. To do that, I planned to approximate the stroke to a polygon and fill it with a scanline algorithm. While I feel confident about implementing ...
53 views

### a very simple raytracer is giving a black output which is implemented in python

I am trying to implement a simple raytracer in python. I am following this tutorial here here is my code, i have explained in comments the relevant parts .All i am getting is a blank image. ...
29 views

### Three quaternions interpolation with barycentric coordinates

I have three quaternions A, B, C. I also have a 3D vector P which describes the barycentric coordinate to interpolate. I want to interpolate the three quaternions with respect to the barycentric ...
24 views

### Does rotating object inside unit cube [-1,1] by homogenous matrix move it outside unit cube

I am just trying to rotate my pointcloud object which is inside the unit cube ([-1,1] in all x,y,z axis). What I did is use the basic rotation matrix from wiki and extend it to homogenuous 4x4 matrix (...
27 views

### How to get “Equal” (saturation, brightness) Red and Green Colours in a Web-based Application?

I am looking for a red and a green hue that are equally discernable against a gray background on any PC monitor, using HTML/CSS-based application. There are many possible solutions to balance these ...
38 views

### Passing mat4 array to GLSL succeeding but producing GL_INVALID_OPERATION

I'm currently passing an array of bone positions to GLSL for a skeletal animation shader; the positions are passing successfully but producing a GL_INVALID_OPERATION error. I'm passing the matrices ...
24 views

### imageStore to a 3D volume in a compute shader does not seem to be working

I am trying to have a compute shader write to a 2x2x2 image3D. It seems to work on ubuntu/mesa/openswr, but it fails on windows/igpu and windows/nvidia1080. It is really the simplest possible code to ...
35 views

### Rotation of meshes in PyTorch

I am doing some project on object reconstruction and I need to rotate an object in PyTorch during the training to make sure I am augmenting the data properly. My data consists of points and it's ...
33 views

### When do I need to use a triangulate function?

I have some misunderstanding about the modeling pipeline. In my mind pipeline are: Concept Sculpt Retopo Baking Rigging Setting Animation Game engine or cartoon/movie ... I read many articles about ...
76 views

### What tris and quads need for?

I know that 3D artists make a 3D model with quads. And they advise to remesh with quads only (if it's possible). So I have some questions: Why do we use quads in CG (for games, cartoons, film, etc) ...
45 views

### Two questions on Gamma correction and Tonemapping

I have few questions regarding tone-mapping and gamma correction. is a tone-mapping operator a function whose output is a value between [0,1] ? If this isn't the case and since gamma encoding ...
24 views

### Visualizing auras around clusters of points

For a real-time application I am trying to add glow to a few hundred points. These points are more like 2D circles of various small sizes on the screen. These points are supposed to be like balls of ...
45 views

### API or Tools to query state of graphics during gameplay?

I’m looking to somehow programmatically query the state of graphics during a PC gameplay session. What I mean by “state of graphics” is, how polygons, textures, lighting and any other scene elements ...
38 views

### Best practices fo OpenGL static buffer data : what is best for performance?

My question is : to allocate static mesh data (vertex/index buffers that never change), is it best : To go the "obvious" way : "1 mesh = 1 VBO", submitting data using glBufferData with GL_STATIC_DRAW ...
19 views

### HLSL texture format RGBA16

I have some gbuffer textures with a RGBA16 format and an hdr skybox as well. I am doing a path tracer and want to clamp some indirect samples to reduce very bright ...
41 views

### Older Api documentation

I am currently using a older IntelHd Gpu which supports Opengl3.1 (Glsl #version140). While trying to locate the relevant Api for this version ,the Khronos site only provides documentation for ...
34 views

### Implicit conversion in glsl shaders

When specifying member values for a structure consisting of float values like vec3 or mat3, is it guaranteed that if an integer ...
33 views

### Does a bumpmap need to be linearized from sRGB when being read?

By a bumpmap, I mean the black and white height map, not the rgb normal map style one. If I were to convert a bumpmap to a normal map then I don't think I should linearize the values because if an ...
65 views

### BRDF sampling and evaluation of diffuse vs specular component

When I am sampling diffuse BRDF I am using cosine-weighted distribution and when I want to sample specular BRDF I use sampling by GGX distribution. I can decide how much light is reflected and how ...
29 views

### Volumetric Photon Mapping - Grid Rendering Artifacts

I am currently implementing a volumetric progressive photon mapping renderer for cloud data (stored as grid density values). As you can see in the image, I am getting this grid with the indirect in-...
48 views

### Given a background image B and a composie image of A OVER B, can we somehow recover image A?

I often find myself in the situation where I have some old image where I composed a translucent overlay on top of a background, but then lost (or more likely discarded) the overlay. I still have pre-...
55 views

### Coloring arbitrary closed regions

I'm trying to implement the following paper in modern OpenGL http://web.media.mit.edu/~lieber/Publications/Coloring-Book.pdf The issue is that the algorithm described requires you to consider ...
115 views

### Correct way to think about Fresnel effect

I am using Schlick approximation to calculate the value of the Fresnel effect I found here When I try to find corner cases for the formula I get the value of 1 when the angle between normal and ...
21 views

### Determine the screen space bounding box of 3D perspetive projected plane

I want to draw a 2D axially aligned rectangle in screen space that covers an arbitrarily oriented 3D projected plane. It sounds easy, just project the 4 corners of the plane, compute the extents, draw ...
81 views

### Understanding of Microfacet monte-carlo path tracing

I am trying to implement BRDF microfacet path tracing and I think I need a little push. I will explain what I understand so that you can correct my mistakes. I start with simple rendering equation: ...
52 views

### Extending an orthogonal set of vectors (graphics application?)

Sorry if this is OT, but I'm wondering if there's a specific graphics technique in which it is required to extend a preexisting orthogonal set of vectors (not necessarily to a full basis, but perhaps ...
93 views

### What is wrong with my metalic PBR shader?

I feel like my light conservation math isn't correct, but I am not sure which part is wrong. Is reflected light supposed to influence the diffuse light? Does metalness only affect the reflected ...
58 views

### Uniform line thickness in plot

I have written a very minimal plotting code which take a function $f$ and a domain $[a,b]$ and plots its graph. (It's here, if relevant.) Now, I query $f$ at the sides of each pixel, and then every ...
48 views

### Vector graphics output from shader program

I’m fairly new to shader programs in general but I have a question concerning vector graphics. I understand that a pixel shader can generate the color information to draw some sort of geometry on ...
35 views

### Does the RGBSpectrum class in pbrt store RGB color values directly, not power?

I had a hard time to understand this. I thought *Spectrum classes (SampledSpectrum, specifically) store power (SI unit: W) in ...
14 views

### How to create a 3D volume model from vtkImageData?

How can I create and save a 3D volume model from a volume image vtkImageData? Some people recommend vtkImageDataGeometryFilter, so I tried the following: ...
89 views

### Interpolation in Graphics Pipeline

I am trying to program my own version of WEBGL graphics pipeline in python, however, I am confused as to where the color interpolation takes place in the pipeline. According to my research, it happens ...
68 views

### Bresenham circle drawing algorithm, compute the distance?

In the Bresenham circle drawing algorithm, we have to choose between the top and bottom pixel, but what we always do is using the circle's equation ($f(x, y) = x^2 + y^2 = r^2$) to determine which of ...
62 views

### Pdf division in BRDF sampling

While following scratchapixel's tutorial on indirect diffuse implementation in path tracing, the samples gets divided by the pdf, which in case of a uniform pdf results in $1/2\pi$ so we have that the ...
36 views

### Isotropic vs Anisotropic Textures

I am reading the paper Texture Synthesis over Arbitrary Manifold Surfaces available here. On page $3$ on the right sight of the page they refer to isotropic and anisotropic textures. I am familiar ...
64 views

### Off by one error when creating face indices

I seem to have an off by one error when creating the indices for the faces of a sphere and I can't understand where. The exact problem is that when I try to calculate the normals of each face a dark ...
17 views

### What need to be change to use Specular/Gloss map in Metallic workflow based PBR shader?

I read the Metallic workflow PBR shader on LearnOpenGL website. I wonder what I need to change to use the specular map. Also searched the conversion between this two map. And this is not that simple ...
25 views

### How to read illum value from mtl file using Assimp library?

I am loading an OBJ file using the ASSIMP library. Following is the MTL file associated with the obj file. ...
122 views

### Understanding BRDF sampling

I'm trying to understand BRDF importance sampling following the exemples of the lambertian/diffuse model and the reciprocal Phong model. I would like to be able to extend the principle to other ...
53 views

### Does WebGL 2 support linear depth texture sampling?

With WebGL 1 we can use WEBGL_draw_buffers extension which lets us use a texture as the depth attachment on the frame buffer. And we can chose to use LINEAR or NEAREST as the filtering method. ...
26 views

### Wrong calculation of the balance heuristic weights in PBRT

Please consider section 16.3.4 of the PBR book, where the authors describe how the balance heuristic weights for the multiple importance sampling estimator in bidrectional path tracing can be computed....
57 views

### Apply Projective Transformation 2D Rectangle

I want to write code from scratch about Projective Transformation in order to apply this transformation to 2d rectangular. I searched about this transformation, but I could not figure out completely. ...
54 views

I have a doubt regarding shape lights pdfs, specifically various sources point at the fact that the pdf is a constant: $$lightpdf = 1/A$$ Where $A$ is the area of the light surface. Expressed in ...
141 views

### Visual Artifact in Wireframe Grid/Plane

I have a simplistic shader program that adds reference coordinate planes to a scene. These planes are drawn as intersecting lines. When viewed at a distance, a visual artifact is created; there is ...
74 views

### SDF rendering for large world

There are lots of cool things you can do with SDFs to render implicit surfaces. Most of the examples I've seen have been “all in the shader”, where the entire distance function is encoded in the ...
41 views

### Queue from a family queue that supports presentation doesn't work [Vulkan]

I'm following this tutorial on Vulkan and I tried to see if it actually worked with different queues for drawing and presenting the image of the triangle. My GPU supports presentation with every queue ...
41 views

### Problem calculating tangent space

I am currently writing a 3D rendering engine for educational purposes. In general everything is working except that I am chasing down a problem in my cube mesh / tangent calculations that I can't find....
96 views

### Calculate normals from vertices

Assume you have a list of vertices and their connectivity information. (I.e you can find all the adjacent edges and faces to each vertex). What is a good approach to calculate a normal from this ...

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