Posts tagged vertex shader
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.
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.
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.