Posts tagged vertex buffer
I’ve chosen the title based on the popular article that tries to prove that OpenGL lost the war against Direct3D. To be honest, I didn’t really like the article at all. First, because it compared OpenGL 3 which targeted Shader Model 4.0 hardware and DirectX 11 which targeted Shader Model 5.0 hardware. Besides that, as we will see, the war is really far from over… This article aims to list the most important features introduced by OpenGL 3.x, OpenGL 4.x, Direct3D 10, Direct3D 11 and we will also talk about the promised features of the upcoming Direct3D 11.1 to be fair with DirectX
Dynamic geometry level-of-detail (LOD) algorithms are very popular and powerful algorithms that provide a great level of rendering performance optimization while preserving detail by using less detailed geometry for objects that are far away, too small or otherwise less significant in the quality of the final rendering. Many of these are used since the very beginning of computer graphics technologies and are present in some form in current CAD softwares, video games and other graphics applications. While determining the appropriate geometry LOD was previously the task of the CPU, with todays hardware it is possible to also offload this to the GPU which excels at handling large amount of objects in parallel.
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.
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.