A technical blog from Daniel Rákos (aka aqnuep)
Graphics
Efficient Gaussian blur with linear sampling
Sep 7th
Gaussian blur
Gaussian blur is an image space effect that is used to create a softly blurred version of the original image. This image then can be used by more sophisticated algorithms to produce effects like bloom, depth-of-field, heat haze or fuzzy glass. In this article I will present how to take advantage of the various properties of the Gaussian filter to create an efficient implementation as well as a technique that can greatly improve the performance of a naive Gaussian blur filter implementation by taking advantage of bilinear texture filtering to reduce the number of necessary texture lookups. While the article focuses on the Gaussian blur filter, most of the principles presented are valid for most convolution filters used in real-time graphics.
Instance Cloud Reduction reloaded
Jun 30th
OpenGL 3.3 - Nature
A few months ago I’ve presented an object culling mechanism that I’ve named Instance Cloud Reduction (ICR) in the article Instance culling using geometry shaders. The technique targets the first generation of OpenGL 3 capable cards and takes advantage of geometry shaders’ capability to reduce the emitted geometry amount in order to get to a fully GPU accelerated algorithm that performs view frustum culling on instanced geometry without the need of OpenCL or any other GPU compute API. After the culling step the reduced set of instance data is fed to the drawing pass in the form of a texture buffers. In this article I will present an improved version of the algorithm that exploits the use of instanced arrays introduced lately in OpenGL 3.3 to further optimize it.
Common pitfalls of iPhone development
May 10th
I haven’t written any posts lately. This is because I dug into iPhone application development and this really consumed most of my spare time. As you may remember, I’ve already mentioned that I would like to start dealing with mobile platforms as a target for my OpenGL related experiments and projects. After Android, this time I got my hands on a Mac mini and took a look at the currently most popular mobile gaming platform. Actually, these initial experiments wouldn’t take that long time if I would have to deal with just a new API and not with a brand new world with its own benefits and drawbacks.
Going mobile with OpenGL ES
Apr 18th
Many things have changed since the first time the public put their hands on the first mobile phone device as these days the end user rarely makes their choices when buying a mobile equipment based on their telephony capabilities. In fact, nowadays these devices are one of the most popular entertainment platforms out there. The main problem for application developers is that these platforms tended to be very heterogeneous from point of view of hardware architecture as well as that of API support. Meanwhile things have changed. While the underlying hardware still varies a lot from device to device the work of application developers has been eased by having cross platform mobile operating systems and open standards. In particular OpenGL ES that is an embedded version of the popular graphics API. In this article I would like to talk about some of the big players of the mobile OS industry and about using OpenGL ES for creating impressive mobile applications.
Sad facts about OpenGL extension libraries
Mar 31st
Everybody who used to make OpenGL applications, whether it be a simple triangle-of-death demo or a comprehensive rendering engine at some point needs to use extensions or later OpenGL versions. Usually many people start this by creating their own initializer library that loads the required entry points from the OpenGL library by hand. What is sure is that at some point everybody realizes that this process is just a waste of time and starts to look for an extension loading library out there. This is the obvious solution as it makes no sense to reinvent the wheel all the time. However, after using a particular one from the repertoire of these libraries one will face the problem that they are not that nice as they seemed before. In this article I will talk about some of these libraries and some of my thoughts about them.
A brief preview of the new features introduced by OpenGL 3.3 and 4.0
Mar 15th
The Khronos Group continues the progress of streamlining the OpenGL API. One very important step in this battle has been made just a few days ago by releasing two concurrent core releases of the OpenGL specification, namely version 3.3 and 4.0. This is a major update of the standard containing many revolutionary additions to the tool-set of OpenGL that need careful examination. In this article I would like to talk about these new features trying to point out their importance and touching also some practical use case scenarios.
Unit testing OpenGL applications
Feb 22nd
Nowadays comprehensive testing is a must for any software product. However, it isn’t such a general rule when it comes to graphics applications. Many developers face difficulties when they have to test their rendering codes. Manual tests and visual feedback is sometimes satisfactory but if one would like to have automated regression tests usual approaches seem to fail. Even if at first sight unit testing of rendering code doesn’t look really straightforward, in fact it is. OpenGL is not an exception from this rule as well. In this article I would like to briefly present a few methods how to unit test OpenGL rendering code and also present my choice and the reasons behind the decision.
Instance culling using geometry shaders
Feb 8th
OpenGL 3.2 - Nature
Since the appearance of Shader Model 4.0 people wonder how to take advantage of the newly introduced programmable pipeline stage. The most important feature enabled by geometry shaders is that one can change the amount of emitted primitives inside the pipeline. The first thing that a naive developer would try to do with it is geometry tesselation. However, the new shader performs very bad when used for tesselation in a real life scenario even though there are demos show casting this possibility. If we take a closer look at the new feature we observe that the most revolutionary in it is not that it can raise the number of emitted primitives but that it can discard them. This article would like to present a rendering technique that takes advantage of this aspect of geometry shaders to enable the GPU accelerated culling of higher order primitives.
Flawless alternative to SDL
Jan 27th
There was always big need for libraries that provide an abstract interface towards the basic platform specific facilities that are necessary for setting up an execution environment for a particular application. In the OpenGL world one of the first such libraries was GLUT. After a while more and more functionalities were put into these libraries that reflect more or less the requirements of application developers. One such framework is SDL. It seems that SDL is still the most respected one of these and it is preferred by the developer community. However, in this topic I will present an alternative that proved its superiority to me in the last few months…
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