# All Questions

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601 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 ...
338 views

### 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 ...
446 views

### Problem with definition of BSDF and radiance

When I was reading theory behind physical based rendering I noticed that definition of BSDF and radiance has some problems. For example BSDF of purely specular surfaces is zero almost everywhere and ...
600 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 ...
450 views

### Using Monte carlo on Rayleigh scattering

Update I am editing and posting this question in a different way; this time from the point of view of Nishita paper. Sunlight gets scattered at P and attenuated before reaching Pv. Therefore ...
197 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 ...
346 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 ...
252 views

### Choosing width of data for signed distance field texture

A signed distance field texture is a technique where you store the distance from a pixel to the surface of a shape within the color information for that pixel, allowing almost vector graphics quality ...
136 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. ...
823 views

### More accurate Fresnel approximation for a RGB-based Path Tracer

I'm writing a path tracer and, for the moment, spectra related data (spectral power distributions and spectral reflectance curves) are stored as RGB tuples. In the Cook-Torrance specular BRDF I am ...
408 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 ...
195 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 ...
1k views

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 $N = ... 0answers 392 views ### Code runs differently on different hardware I wrote a 2D fluid-solver in OpenGL (code here) some time back. While it runs flawlessly on my onboard Intel GPU, the simulation very quickly "blows-up" when same code is run using nvidia card : ... 1answer 2k views ### How to draw an orthogonal graph from its edges and vertices data? I am writing a software and I need to represent an graph in a orthogonal manner from topological data (vector of edges,vertices and their connectivity data) Graphs consist of a set of vertices and a ... 0answers 112 views ### Noise shaping for dithering with gamma? The context of this question is correct dithering of color with gamma correction. In dithering we add (shaped) noise$n$to a signal$s \in [0, 1]$based on a random variable$r \in [0, 1]$s' = s +... 0answers 276 views ### Avoiding Mach band effect when using multiple lights I wrote a simple Phong shader with two directional lights for a project, and noticed an unpleasant artifact in the lighting. Where both lights are illuminating the same region, dark bands appear at ... 0answers 381 views ### How does path tracing handle specular surfaces(Dirac BSDFs) such as water? I'm trying to render water using path tracing. However, since in path tracing, the light sampling is skipped while the intersection point is perfect specular and thus no direct light would be taken ... 0answers 223 views ### How is Ambient Occlusion calculated in “Deep Screen Space”? The paper (http://resources.mpi-inf.mpg.de/DeepScreenSpace/) just says that "The ambient occlusion contribution of a surfel to a pixel [..] as well as the influence radius [..] are computed ... 0answers 1k views ### Diffuse BRDF component of the Disney BRDF In the SIGGRAPH course: BURLEY B.: Physically Based Shading at Disney, SIGGRAPH 2012 Course: Practical Physically Based Shading in Film and Game Production, 2012. it is mentioned that some BRDF ... 0answers 199 views ### Dual paraboloid shadow texture edge seams I implemented dual paraboloid shadows for point lights. The goal was to reduce the number of shadow passes. Also the target is GLES3.0 so no layered rendering is available. The shadows work, and ... 0answers 684 views ### OpenGL texelFetch causes black stripes THE SHORT VERSION In my fragment shader I'm reading (using texelFetch) multiple times the same texel from a texture (created by another fragment shader) and write it to the output render buffer. ... 0answers 86 views ### Form Factors confusion in Radiosity papers I feel a bit confused about the use of$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 ... 0answers 391 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 ... 0answers 180 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 ... 0answers 128 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 ... 0answers 218 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 ... 0answers 260 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 ... 0answers 154 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 ... 0answers 128 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 ... 0answers 52 views ### Ask for help on understanding a formula related to change of variable Although I have tried for a long time, I cannot understand Eq.(11) of paper "Microfacet Models for Refraction through Rough Surfaces" written by Bruce Walter, Stephen Marschner, Hongsong Li and ... 0answers 168 views ### Ray tracing implicit surfaces using Sturm's theorem I am trying to render implicit surfaces given by a polynomial equation$F(x,y,z) = 0$using Sturm's theorem. Plugging the parametric ray equation$r(t) = o + td$, where$o\in\mathbb{R}^3$is the ray ... 0answers 64 views ### Drawing “after” Present to achieve better performance I had an application that was originally single threaded and worked as follows: gather the items to be drawn (occlusion / frustrum culling / sorting into batches) draw items using an immediate ... 0answers 304 views ### In Metal, what performance advantages are there, if any, to using vertex descriptors and the [[stage_in]] qualifier? Metal seems to provide two very different ways to access vertex data in your vertex shader. You can: Create an MTLVertexDescriptor object, which describes vertex ... 0answers 202 views ### Computation of conservative AABB for clipped triangle I'm currently trying to implement a fast algorithm for KD-Tree construction using SAH, as described in this paper: On building fast KD-trees for ray tracing, and on doing that in O(N log N) I found ... 0answers 157 views ### CrazyBump Shape Recognition I've recently been using CrazyBump, and I think I'm starting to understand how it works. But I'm confused about what it calls Shape Recognition. According to this website, that feature attempts to add ... 0answers 136 views ### What is the potential equation in PBR? I'am studying PBR and the book introduce the potential equation. They said the potential equation can describe shooting algorithms better, and$W(x, \theta)$describes the fraction of the radiance$L(...
548 views

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-...
119 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 ...
701 views

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......
61 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 ...
93 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 ...
659 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 ...
252 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 ...
122 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 ...
726 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 ...
87 views

### Visualize the interpolated unit quaternion on the surface of the unit sphere

My major is mechanical, please forgive me for asking questions that may seem trivial to you. First, I'm reading the following paper: Dam, Erik B., Martin Koch, and Martin Lillholm. Quaternions, ...
81 views

### Are there any reasons to use power of two textures with modern mobile platforms?

Are there any reasons to use power of two textures (like 128x128 sized) if one targets modern mobile platforms (with OpenGL ES 3.0, Metal and/or Vulkan)? With iOS the PVRTC only supports power of two ...
200 views

### Proper way of consuming stratified samples in path/ray tracing

I'm working on a (toy-level) path/ray-tracer, currently trying to implement (and understand) improved sampling strategies. The obvious next choice after uniform random sampling would be stratified/...
160 views

### Pre-filtered environment map, deriving the equation

I'm reading through this article, and more specifically I'm trying to derive the equation that would explain the implementation the following shader (still in the same article): ...

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