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16 votes
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Why does increasing simplex noise dimension wash it out?

I just tried using this approach to create a tiling 2d simplex noise function with Gustavson's java implementation. The result tiled, but the texture seemed muddy / washed out. I decided to compare ...
Pikalek's user avatar
  • 377
16 votes
0 answers
807 views

What exact algorithm and parameters reproduce L-system plant growth figure in Algorithmic Beauty of Plants

I am interested in duplicating a figure (shown below, ch 1 fig 1.21) in the book Algorithmic Beauty of Plants. The book is available here http://algorithmicbotany.org/papers/#abop This image appears ...
Martin Krzywinski's user avatar
12 votes
0 answers
864 views

How correct is rendering in XYZ / linear RGB space?

I have a spectral power distribution (SPD, 5 nm steps) for all light sources in the scene and SPDs for the reflectance of all surfaces under any light / viewer angle in question. I'm going to ...
David Kuri's user avatar
  • 2,293
10 votes
0 answers
169 views

How to describe the bi-directional links for the Weiler-Atherton algorithm?

My postscript interpreter currently implements the Hodgeman-Sutherland clipping algorithm but this is limited to simpler shapes and doesn't have a provision for utilizing various winding-number rules. ...
luser droog's user avatar
  • 1,378
9 votes
0 answers
2k views

Diffuse BRDF component of the Disney BRDF

In the SIGGRAPH course: BURLEY B.: Physically Based Shading at Disney, SIGGRAPH 2012 Course: Practical Physically Based Shading in Film and Game Production, 2012. it is mentioned that some BRDF ...
Matthias's user avatar
  • 1,084
9 votes
0 answers
292 views

Help with start up bias in Metropolis Light Transport

I'm trying to implement metropolis light transport based on this paper, and I have the basic thing working. I run the algorithm multiple times with different starting points, add the results for each ...
devil0150's user avatar
  • 191
9 votes
0 answers
560 views

WebGL packing/unpacking functions that can roundtrip all typical 32-bit floats

I have a WebGL circuit simulator. One of the problems it has is that, due to using quite a lot of intermediate float textures as it simulates, it doesn't work on various mobile devices. They only ...
Craig Gidney's user avatar
9 votes
0 answers
489 views

3D mesh segmentation simple algorithm

I am developing the algorithm reported in this article: Least square conformal mapping. Here is presented an algorithm to flat a 3d mesh on the parametric space, but i don't understand the ...
Mugna's user avatar
  • 91
8 votes
0 answers
726 views

Code runs differently on different hardware

I wrote a 2D fluid-solver in OpenGL (code here) some time back. While it runs flawlessly on my onboard Intel GPU, the simulation very quickly "blows-up" when same code is run using nvidia card : ...
nilspin's user avatar
  • 81
7 votes
1 answer
708 views

How to match Blenders polynomial lens distortion model with GLSL?

I'm trying to re-implement Blenders (libmv) polynomial lens distortion model using shadertoy, in order to apply the lens distortion in another application ideally by generating a STMap for that. I ...
brockmann's user avatar
7 votes
0 answers
256 views

Supersampling HDR

I'm encountering some issues supersampling in HDR for an SDR result and was curious what the usual method for doing this is. Notice how pixelated the edge of the white sphere is. Here's how I render ...
Alan Wolfe's user avatar
  • 7,801
7 votes
0 answers
2k views

Bump mapping a ray-traced sphere

I'm attempting to apply a height map to a ray-traced sphere. The height map is stored as a texture. I have the intersection point on the sphere $p$, and I compute the normal vector at that point $N = ...
Walt Donovan's user avatar
7 votes
0 answers
737 views

Perspective-Correct Texture Mapping

I am working on a small rendering engine for a personal project and I am having issues with the texture mapping part of it. It seems to work for some cases, but not for others. For example, when one ...
neat's user avatar
  • 71
7 votes
0 answers
304 views

Cannot use more than a couple of MB in a shader storage buffer

I am implementing a simple ray tracer with OpenGL. I have a shader storage buffer with all the triangles so I can test them for intersections in a compute shader. It works fine up to a certain buffer ...
gartenriese's user avatar
7 votes
0 answers
142 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 ...
user3059485's user avatar
6 votes
0 answers
911 views

How to implement PCSS correctly?

I'm trying to implement PCSS in OpenGL/GLSL, but I have problems understanding the details especially the conversions between the coordinate spaces. The existing implementations are so different from ...
racz16's user avatar
  • 161
6 votes
0 answers
233 views

Noise shaping for dithering with gamma?

The context of this question is correct dithering of color with gamma correction. In dithering we add (shaped) noise $n$ to a signal $s \in [0, 1]$ based on a random variable $r \in [0, 1]$ $$s' = s +...
orlp's user avatar
  • 186
6 votes
0 answers
743 views

How to account for self intersection with large ray tracing scenes?

I'm working on a hybrid real time ray tracing project and trying to tackle the problem of self-intersection with larger scenes due to loss of float accuracy. The logic I'm trying to use is based on ...
Florian Schut's user avatar
6 votes
0 answers
622 views

Avoiding Mach band effect when using multiple lights

I wrote a simple Phong shader with two directional lights for a project, and noticed an unpleasant artifact in the lighting. Where both lights are illuminating the same region, dark bands appear at ...
russ's user avatar
  • 2,402
6 votes
0 answers
606 views

How does path tracing handle specular surfaces(Dirac BSDFs) such as water?

I'm trying to render water using path tracing. However, since in path tracing, the light sampling is skipped while the intersection point is perfect specular and thus no direct light would be taken ...
jinglei's user avatar
  • 293
6 votes
0 answers
238 views

How is Ambient Occlusion calculated in "Deep Screen Space"?

The paper (http://resources.mpi-inf.mpg.de/DeepScreenSpace/) just says that "The ambient occlusion contribution of a surfel to a pixel [..] as well as the influence radius [..] are computed ...
donutboy's user avatar
  • 143
6 votes
0 answers
494 views

In Metal, what performance advantages are there, if any, to using vertex descriptors and the [[stage_in]] qualifier?

Metal seems to provide two very different ways to access vertex data in your vertex shader. You can: Create an MTLVertexDescriptor object, which describes vertex ...
lcmylin's user avatar
  • 413
6 votes
0 answers
1k views

Cascaded shadow maps. Seams between cascades

I implemented cascaded shadow maps, where shadow maps for each cascade is rendered to one canvas: The light projections for each cascade are calculated from the bounding spheres of camera sub-...
Zheden's user avatar
  • 161
6 votes
0 answers
1k views

OpenGL texelFetch causes black stripes

THE SHORT VERSION In my fragment shader I'm reading (using texelFetch) multiple times the same texel from a texture (created by another fragment shader) and write it to the output render buffer. ...
Christian_B's user avatar
6 votes
0 answers
124 views

Form Factors confusion in Radiosity papers

I feel a bit confused about the use of $F_{ij}$ and $F_{ji}$ in Radiosity papers. $F_{ij}$ should be the fraction of energy leaving patch $i$ that arrives at patch $j$. If you take the original ...
cesss's user avatar
  • 161
6 votes
0 answers
946 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 ...
Paweł Pela's user avatar
6 votes
0 answers
347 views

scan line conversion

I am going throug the topic scan line conversion where the scan line parallel to the x-axis is put through the intersection test with all the edges of the polygon. Would there be any large ...
sajis997's user avatar
  • 1,279
6 votes
0 answers
129 views

How much processing power does stenciling actually save?

For example, let's assume I'm rendering cascaded shadow mapping, but for whatever reason, instead of one of the typical approach, I do the following: Render the lowest resolution shadowmap Copy part ...
Llamageddon's user avatar
5 votes
0 answers
61 views

Facetted look when using SampleBias

I am writing a simple material system for a game. Each material can have a specular value (phong) that is translated into "smoothness" via environment map. Similar to PBR, I compute a ...
Raildex's user avatar
  • 173
5 votes
0 answers
525 views

Where do "fireflies" come from?

I'm using a renderer developed by other people, and I found there are fireflies. It is strange that in a completely diffuse scene, there are still fireflies presented. To my understanding, I think it ...
AccM's user avatar
  • 61
5 votes
0 answers
321 views

Why is Forward Rendering/Shading named this way?

Forward rendering is the 'classic' approach to the rendering pipeline. Nowadays it is mostly replaced by a more flexible, deferred rendering approach. I did some research and had trouble finding ...
LukeG's user avatar
  • 151
5 votes
0 answers
214 views

How to use Photometric Units with Rendering Equation?

So I was just reading up on how to create more Physically Based Lights and wandered into the realm of photometry. I read the paper "Moving FrostBite to PBR" and in it the author claims he decided to ...
gallickgunner's user avatar
5 votes
0 answers
391 views

Computation of conservative AABB for clipped triangle

I'm currently trying to implement a fast algorithm for KD-Tree construction using SAH, as described in this paper: On building fast KD-trees for ray tracing, and on doing that in O(N log N) I found ...
Michal Kučera's user avatar
5 votes
0 answers
140 views

What is the potential equation in PBR?

I'am studying PBR and the book introduce the potential equation. They said the potential equation can describe shooting algorithms better, and $W(x, \theta)$ describes the fraction of the radiance $L(...
shashack's user avatar
  • 523
5 votes
0 answers
284 views

Dual paraboloid shadow texture edge seams

I implemented dual paraboloid shadows for point lights. The goal was to reduce the number of shadow passes. Also the target is GLES3.0 so no layered rendering is available. The shadows work, and ...
Michael IV's user avatar
5 votes
0 answers
136 views

Is there any open-source implementation of n*log(n) visibility graph construction algorithm?

Is there any open-source implementation of n*log(n) visibility graph construction algorithm? I'm trying to understand S. K. GHOSH and D. M. MOUNT sweep line algorithm, but it's known for having very ...
Ibraim Ganiev's user avatar
5 votes
0 answers
1k views

Percentage-closer Soft Shadows implementation

I am trying to implement the Percentage-closer Soft Shadows (PCSS) from NVidia inside Unity but I am facing some issue and I don't know where they come from and then, I do not know how to solve them......
MaT's user avatar
  • 1,229
5 votes
0 answers
65 views

Early exit strategy for SSAO

I'm working on an SSAO implementation. I've had an idea to speed it up by having AO fragment shader finish faster for fragments that are not occluded (depending on the scene, this can be a significant ...
nicebyte's user avatar
  • 151
5 votes
1 answer
3k views

How to draw an orthogonal graph from its edges and vertices data?

I am writing a software and I need to represent an graph in a orthogonal manner from topological data (vector of edges,vertices and their connectivity data) Graphs consist of a set of vertices and a ...
Iman Nia's user avatar
  • 283
5 votes
0 answers
160 views

Polygon Filling rule - even odd OR orientation of the normal

I am going through some ideas that slice a 3D model and fill the area of the resulting polygon contour . Currently they are using the following concepts as follows: Every resulting line of the ...
sajis997's user avatar
  • 1,279
5 votes
1 answer
2k 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 ...
dialer's user avatar
  • 151
5 votes
0 answers
255 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)...
RCountZero's user avatar
5 votes
0 answers
1k views

How to disable Perspective Correction in Texture Coordinates Interpolation in OpenGL(without using shaders)?

I need to do planar reflection mapping in OpenGL. By using a virtual camera (with a reversed camera ray) at the back of reflective plane (a mirror), I rendered the scene to texture, which is then ...
DQLin's user avatar
  • 51
5 votes
0 answers
323 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 ...
Marqin's user avatar
  • 151
5 votes
0 answers
351 views

Indexing gl_TessLevelOuter[] with gl_InvocationID on a tessellation control shader

I'm using hardware tessellation to render a terrain mesh with variable LOD. I have this snippet on my tessellation control shader: ...
MadEqua's user avatar
  • 238
5 votes
0 answers
366 views

Incorrect instanced rendering

Previously, to render a bunch of quads, I was simply using a few uniforms (one for a model matrix and another for the texture layer ID). However, I'd rather not have to loop through each quad and set ...
Darkilon's user avatar
5 votes
0 answers
420 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 ...
Michael IV's user avatar
5 votes
1 answer
2k views

Manually fetching 8 neighboring texels from 3D texture greatly decreases performance

I'm implementing manual interpolation between texels in a 3D texture to be able to discard some of them when needed. Compared to hardware interpolation, this process takes a lot of time. If I simply ...
Pavlo Muratov's user avatar
4 votes
1 answer
136 views

How to remove a control point from a NURBS curve?

I am trying to write an algorithm to remove a control point from a NURBS curve, similarly to what can be achieved using the CVREMOVE command in AutoCAD. I searched online but I was unable to find a ...
Lorenzo Celli's user avatar
4 votes
0 answers
589 views

Watertight Mesh Representation

A watertight mesh is one which does not have holes, and for which each face has a designated inside and outside. Such a mesh can be "tetrahedralized", has a defined volume, and can be an ...
Joshua Hyatt's user avatar

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