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6
votes
1answer
2k views

What's the difference between irradiance and fluence/radiant exposure?

A paper$^1$ I'm reading says fluence measures the incoming radiance from all directions and that fluence is similar to irradiance. It's defined by $\phi(x) = \int_{4 \pi} L(x, \vec{\omega'}) d\omega' $...
5
votes
1answer
211 views

Silhouette curve for isometric surface of revolution

I am trying to figure out how to convert a flat representation of a curve into the silhouette of a surface of revolution in a isometric projection. In essence in want the planar cut of the surface ...
14
votes
1answer
395 views

Need a reputable source for the formula for the shape of Earth's horizon

What I'm asking for I stress that I am not asking for the formula---I know the formula, and how to derive it. Several different versions of it are reproduced near the end of the post. In fact, ...
3
votes
2answers
1k views

How do I create my own bitmap using a text editor?

I'm a Computer Science student who's been getting into bitmaps & pixmaps recently. I clearly understand what pixmaps do. A pixmap, as I understand, defines each pixel individually. So, maybe I ...
3
votes
2answers
979 views

How to determine the object-to-world matrix

I want to ray trace a triangular mesh that I load from a file. The vertices' coordinates are expressed in the reference frame associated with the object (i.e the mesh) and I don't know the object-to-...
9
votes
2answers
377 views

Reliable test for intersection of two Bezier curves

How to reliably find out whether two planar Bezier curves intersect? By "reliably" I mean the test will answer "yes" only when the curves intersect, and "no" only when they don't intersect. I don't ...
4
votes
1answer
1k views

VR stereo rendering with Instancing

I have been reading this paper by Timothy Wilson Fast Stereo Rendering for VR and it would suit our game engine (DirectX 11) to use this method of stereo rendering. I have managed to get the game ...
1
vote
1answer
90 views

reconstruction drawing sequence from video

I have a video that record the drawing sequence with a pencil by a painter. I want to reconstruction the sequence from the video. And I have google some keywords like drawing sequence reconstruction, ...
8
votes
2answers
232 views

How to create a patterned object with variable pattern density in real-time?

Assume there is some value p, calculated per-frame, that varies continuously over the surface of an object. The value of p ...
5
votes
1answer
523 views

Type conversion to GL-types

If I have a std::vector<Foo> and want to store its size in a GLuint, my compiler gives a warning that there is possible ...
8
votes
2answers
1k views

What makes a good permutation table?

I'm implementing improved Perlin noise. Its key feature for randomisation is the hardcoded permutation table, which gives essentially random but reproducible gradients at the cells of the grid. The ...
3
votes
1answer
303 views

GDDR5 vs. DDR3 for learning GPU programming on a limited budget?

[Please (kindly) let me know if this is not the place for this question] I'm hoping to learn about GPU programming, but as a college student, I've a quite limited budget. I'm wondering whether I ...
9
votes
2answers
510 views

How updating a depth buffer works in GPU?

Right now I'm trying to implement some sort of depth buffer in software and I have a huge problem when I'm writing to it. Having one mutex is absolute overkill. So I created a number of mutexes equal ...
3
votes
2answers
303 views

How is Raster and Random Scan Display different?

Raster scan display forms an image with pixel whereas a Random scan display works with Geometric primitives, but even a geometric primitve( a line) is made up of pixels so what is the difference?
3
votes
1answer
86 views

Is there a way to script image creation?

I am facing a though challange - I need to perform repetitive Image formating. Firstly, I need resize picture A so that it has some fixed width in pixels. Then, I need to place picture A in the middle ...
3
votes
2answers
768 views

GPU Architecture: What are the theoretical limits on triangle throughput in modern GPUs?

For each of major vendor's latest GPU architectures, is there a clear maximum "triangles/second" bottleneck? If so, what is it architecturally and what is the performance?
1
vote
1answer
476 views

Ray tracing - tangent space for a point on a sphere

In a ray tracer, given a point on a sphere (point_of_intersection with a ray) and its normal for that point (point_of_intersection - center_of_sphere) how do I calculate the tangent space for that ...
1
vote
0answers
31 views

Optimise drawing contour maps representing gravity

I'm drawing a contour map representing gravity. The algorithm is: For each point on the screen (1 pixel per point) I calculate the gravitational pull for each object and combine (using Newtons law ...
3
votes
2answers
868 views

How enlarge parts of a video like snapchat lens filter

I writing the this video process app which requires the each video frame to be processed such that parts of the video are enlarged. As a reference, one of the snapchat lens filter enlarges the eyes of ...
3
votes
1answer
626 views

Shadow appears to be too dark in my ray tracer

I'm currently working working on a unbiased path tracer. To test how accurate it is. I created a scene in my path tracer and LuxRender then compare the rendered image. I found that the shadow in the ...
5
votes
2answers
178 views

Low Pass filtering

Is it possible that low pass filtering can be applied to Ray tracing ? My guess is that since after the algorithm runs we have an image then low pass filtering helps in order to prevent aliasing ...
5
votes
3answers
2k views

Is it possible to create minimal glTF files with vertex and index buffers?

I am currently looking into glTF to use as a transfer format for my WebGL project. I already have the geometries I wish to render on my WebGL client available as preprocessed vertex and index buffers (...
5
votes
1answer
175 views

Why is rotating this prism in iOS Metal not rendering correctly?

I've set up a test project for learning Metal on iOS to do some rendering, but I'm a bit stumped on how to get a prism rotating correctly about its y axis. Here is the prism rendered without depth ...
2
votes
1answer
90 views

Slide a rectangle along a sphere

I'm using NASA WorldWind to place a rectangle on the Earth ('sphere'). When I drag the rectangle on the sphere, the rectangle changes shape and size but the dimensions should be preserved. What is ...
5
votes
1answer
232 views

Ray tracing - BRDF using Cornell measured spectral data

I wrote a ray tracer that implements various BRDF models (Oren Nayar, Lamber, Torrance Sparrow and so on). Now I'm trying to implement a BRDF from measured data. I choose the Cornell database data ...
10
votes
1answer
149 views

Reasons of the assumptions for the microfacet distribution function?

The paper Microfacet Models for Refraction through Rough Surfaces (among others) reminds us the following assumptions about the microfacet distribution function D: Microfacet density is positive ...
6
votes
1answer
95 views

using importance sampling to reduce the error of outscattered radiance

http://renderman.pixar.com/view/implementing-a-skin-bssrdf In this paper on subsurface scattering, I'm trying to understand how importance sampling is used to compute single scattering. It says that ...
1
vote
1answer
695 views

Is back-face culling considered a technique/optimization of ray tracing?

I've stumbled upon this question on a CG exam: Which of the following techniques/optimizations doesn't apply to ray tracing? A: Back-face culling B: "Shadow-feeler" rays C: Recursive ...
9
votes
1answer
155 views

Per Vertex Computation in OpenGL Tesselation

I try to implement a position based cloth simulation using hardware tesselation. This means I want to just upload a control quad to the graphics card and then use tesselation and geometry shading to ...
1
vote
1answer
664 views

Outcodes in Cohen-Sutherland Clipping Algorithm

What advantages do the outcodes offer in this algorithm ? Do they help in simplifying the algorithm ? Do they decrease the number of calculations ?
5
votes
1answer
204 views

Shadow map projection issue

I am using Unity but this question might not be proper to this engine. I have projected the shadow map onto this sphere but there are grazing shadows. Is it possible to avoid it or to correct it as I ...
10
votes
1answer
568 views

What does “muted” mean in the context of color?

I want to extract colors from images like in Adobe Kuler. When I select colorful or muted corresponding colors are shown. But what is the definition for colorful or muted colors? What do the words "...
2
votes
0answers
762 views

Problems in using cox regression with restricted cubic spline plot with R software

In R software, I want to plot a graph by using cox regression with the restricted cubic spline method. However, I can't quite get it to work. This is the code I'm using: ...
5
votes
1answer
444 views

Methods for grid traversal in a glsl pixel shader?

I'm working on a shadertoy "snake" game, using the new multi pass rendering abilities to save game state between frames. I'm using raytracing to render the board (an AABB), and am planning on using ...
4
votes
1answer
472 views

Shader won't work

I have managed to implement a garoud shader with specular lighting efects in Processing 3.0 . Now I am trying with a fragment Phong shader but cannot make it work. I can´t find where is the error. It ...
8
votes
1answer
547 views

How should I fill a shape consisting of Bezier curves and straight lines?

I have been working on a graphics library for some time now and have gotten to the point where I have to draw Bezier and line based fonts. Up to this point I am stuck with this: The green lines are ...
4
votes
1answer
234 views

Spine. What is the name of the process?

https://www.youtube.com/watch?v=twUz99ek5do&list=WL&index=5 There is a process from 1:51, where the guy start making polygons around the bodyparts. I think this is this part is where (with ...
1
vote
0answers
99 views

Selecting pixels within a circle having a decimal (non integer) radius

I want to select a pixel within a circle of a certain radius. But the radius is expressed in a decimal form (0.12). What does it mean to have a radius equal to 0.12? And concretely how to pick a pixel ...
4
votes
0answers
272 views

How to make double working in OpenGL 4.1 on OS X ( Intel HD Graphics 5000 )?

I've recently rebuild shaders for my program and it stopped "working" ( black screen ) on OS X ( El Capitan ), but it's ok on Linux on GTX 660. I've tested it on another Apple hardware and it worked ...
5
votes
1answer
160 views

How should I generate the view position for a light at infinity when creating depth maps?

I'm working on implementing Bruneton's cloud rendering paper, which requires one to render a pair of depth maps, similar to how shadow mapping works. In this case, my light source is the sun (or ...
6
votes
1answer
548 views

Flat shading for non-planar polygons

I'm trying to figure out how to properly implement flat shading for meshes containing non-planar polygons (using OpenGL/GLSL). The aim is to obtain something similar to the result Blender gives (all ...
7
votes
1answer
549 views

How to implement a realtime 2D light renderer with fog/colored light on the GPU?

Since long ago I wanted to implement a 2D lightning algorithm based on an idea I saw on YouTube. The video is realtime, but it runs on the CPU and the resolution is pretty low. I'm curious if anyone ...
4
votes
2answers
388 views

OpenGL vertex color

Why do I need to specify the same name for color input in fragment shader and output color from vertex shader? ...
6
votes
1answer
166 views

What is the state-of-the-art on using computers to “clean-up” images?

TWO PART QUESTION - We've all seen the movies/TV shows where the police/feds/spies use computer software to take a grainy photo and do a "clean-up" to see a better picture and more details. I assume ...
4
votes
1answer
139 views

Multiple light pixel Shader in GLSL

I have wirtten a fragment shader that works just fine with a single light. Now I am trying to adpat it to work with 8 lights, the implement it in Processing. Clearly I am doing something wrong in the ...
9
votes
3answers
698 views

What are the usages of software rasterization in modern game engines?

I am taking a Computer Graphics course this quarter. One of our lab project is about software rasterization. Now I am planing the project proposal and thinking about how to make it useful for other ...
13
votes
1answer
5k views

How to map square texture to triangle?

I want to find the texture coordinates for point P. I have the vertices of the triangle and their corresponding uv coordinates. The numbers in the little squares in the texture represent color ...
8
votes
3answers
1k views

How does a computer upscale 1024x768 resolution to 1920x1080?

Without there being black bars I mean. 1080 isn't any multiple of 768 so is there some sort of data loss?
2
votes
0answers
230 views

Projecting light shapes

I am wondering how professional light visualizer software (like Capture Argo - WYSIWYG - Realizzer - LightConverse) project the lights on the objects (like stage, floor, people), even projecting the ...
6
votes
0answers
124 views

Injecting Virtual point lights into 3D Grid

I am currently trying to implement light propagation volumes in DirectX 11 and I have already done the RSM part which contains position, normal, depth and flux map generation. But for Injecting ...

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