Doug Binks - 05 Sep 2015
This is the second in a series of articles detailing the inner workings and evolution of the permissively open source multithreading task scheduler enkiTS for C and C++ (including C++ 11). In the first article of this series I covered the external interfaces and their implementation. This post will cover the task threading function, running tasks, and waiting for tasks.
Figure 1: Screenshot of Avoyd being profiled with microprofile and ImGui integration available in enkiTSExamples. Solid bars above named tasks show when threads are active - the wait functionality allows the core to idle or other threads to run.
Doug Binks - 22 Aug 2015 - edited 27 Aug 2015
This is the first in a series of articles detailing the inner workings and evolution of the permissively open source multithreading task scheduler enkiTS for C and C++ (including C++ 11).
enkiTS - Code and basic examples for the task scheduler described this article.
If you're writing a compute intensive programming task on consumer hardware, and you want to use as much of the systems resources as possible, then you'll need to consider multithreading on the CPU. There are a number of ways to approach this, but the current gold standard approach for developers who want both simplicity and control is a task scheduler which can handle data-parallelism (in the games industry a task is often referred to as a job). Task parallelism allows you to run different types of computation at the same time, whilst data-parallelism enables you to run the same computation over a set of data across different threads at the same time. Note that I won't consider Single Instruction Multiple Data (SIMD) parallelism here, but if you're doing computations you probably should. Additionally, I won't cover multithreading methods for handling large latency, such as waiting on hard disk or socket transactions.
Doug Binks - 31 Jan 2015
As usual, whilst working on one aspect of Avoyd I hit a hurdle and decided to take a break by tweaking some visuals - specifically looking at the normals for my surfaces. I added a step to generate face normals in the pixel shader using the derivatives of world space position [see: Normals without normals by Angelo Pesce and the Volumes of Fun wiki on Computing Normals], and immediately noticed precision issues when close to the surface. I'll demonstrate the issue and my quick fix which uses eye relative position instead of world space, before explaining what's happening in full.
Doug Binks - 22 Oct 2014
In this post and video I'm going to cover the recent changes I've made to Avoyd's technology to add shadows, ambient occlusion and procedural texturing. I'll describe simple procedural texturing and its anti-aliasing, along with the use of voxel octree data to generate lighting and ambient occlusion using ray casts and 3D textures in the game Avoyd.
There's a good deal of information on all of these topics online, and they certainly aren't novel additions to a game - however in Avoyd I'm taking a slightly unusual approach so I thought it worth documenting. It's worth checking out the video before reading further.
Doug Binks - 27 Feb 2014 - edited 27 Oct 2014
The video showcases three players zooming around at high speed in an environment being streamed from one player's PC to the other two, with the recording being done on one of the clients. This devblog post is about the steps I took to get this working smoothly.
Performance tuning is a large and varied topic, so I'm going to concentrate on one aspect which came up during development of the streaming system - framerate hitch removal. A framerate hitch occurs when one frame takes longer than most of the rest of the frames. To the player it can feel like a sudden start/stop. If frequent, the game takes on the feeling of being played on sandpaper.
Doug Binks - 16 Jan 2014
This tech update video shows off multiple players rapidly and smoothly editing fairly large sections of the environment whilst in edit mode. Materials and rendering are all still simple debug visuals for clarity rather than beauty, but there's still a fair degree of artistic freedom available. It's a real pleasure being able to carve and paint geometry fluidly in a connected online world.
Getting this to work, and work well, took a fair amount of effort and I'll explain some of the technical details here.
Doug Binks - 14 Jan 2014
The post follows on from the earlier post on Octree Streaming. You should be able to read them out of order, but you get cake if you read part 1 first.
Our latest tech update video shows off players moving through the world shortly after joining the game - the video starts only a few seconds after where the last one ends, so about 30 seconds after loading. At this point large sections of the world are still being streamed to clients, but the prioritization of nearby regions ensures detail is present close to the player.
Doug Binks - 12 Jan 2014
The original Avoyd stored the internal voxel representation of its game world as a standard 3D array. At the time this provided a good trade off between performance and memory for the size of levels we required for a multiplayer PvP game with a fully modifiable environment. In the new version we wanted to increase the size of worlds we could handle, whilst maintaining large view distances.
Our second technology update video shows off how the voxel octree streaming gives rapid loading over the internet.
Doug Binks - 05 Dec 2013
I was recently testing my LAN server browser dialogue menu with multiple machines running servers when I encountered an unusual issue. I had two machines, each running a server and a client. On one machine the client could see both servers, but on the other machine only the local server was found. The application had firewall permissions, and since the server was both sending and receiving packets without problem the firewall didn't seem to be the culprit.
Working LAN discovery with two servers running on two different machines. Note the two IP addresses listed for Machine 1.