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Refresh your Memory: Advanced Graphics Algorithms
subtle writes "DevMaster.net has posted an interesting article about advanced graphics algorithms. The article discusses six widely used algorithms in graphics rendering of indoor and outdoor environments, namely: quad-based static terrain, Roettger's approach to continuous levels-of-detail in terrain, real-time optimally adapting meshes, portals, BSPs and PVSs. In each case the algorithm is discussed and some aspects of implementation are considered, as well as analyize each algorithm for its application in modern graphics systems."
I look forward to re-doing my back yard with a nice quadratic mesh algorithm with pseudo-fractal post-processing.
Don't blame Durga. I voted for Centauri.
AWESOME Rock Music Here
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Advanced Graphics Algorithms
By: Henri Hakl
1. Introduction
Graphics representation of reality - or at least virtual reality - in games, simulations, movies, commercial and military applications have become increasingly convincing and immersed a growing audience in disbelieve - and at times even utter belief. This process has, in part at least, been facilitated by exponentially growing processing speeds and in more recent years the advent of hardware acceleration of graphics rendering.
However, even in spite of being able to process several giga-flops every second, a brute force approach to rendering is not able to produce nearly as realistic real-time environments and worlds as we find portrayed in games and interactive simulations. The reason is that numerous algorithms are used that approximate or compromise reality in order to achieve interactive rendering rates. These algorithms include methods to simplify scenes, to efficiently cull invisible parts or to simply ignore realistic computations in favour of faster approaches that, though inaccurate, portray reality.
Following the introduction we present a section on several graphics rendering concepts that feature in this article. In the remainder of this article we will discuss six popular algorithms for indoor and outdoor rendering of environments, namely:
quad-based static rendering of environments
a continuous level-of-detail (CLOD) rendering of height fields as described by Roettger et al [1]
real-time optimally adapting meshes (ROAM) for terrain rendering
portal-based rendering of indoor environments
binary space partitions (BSP) of indoor environments
potential visibility sets (PVS)
We will discuss each approach, offering a high-level description of each as well as implementation considerations where appropriate. Finally each algorithm will be discussed in terms of its application in modern graphics system before we conclude the article.
2. Concepts in Graphics Rendering
This section offers a broad overview into several key concepts in graphics rendering. These include the graphics pipeline, vertex representations, scene reduction techniques and graphics models - for a more extensive description we refer the interested reader to Alan Watt's 3D Computer Graphics [2].
2.1 The Graphics Pipeline
Graphics rendering is concerned with reducing a scene, a collection of three-dimensional data, to a smaller, visible subset and rendering this subset. To render a scene subset we note that a scene consists of polygons that are usually reduced to sets of triangles for hardware rendering purposes. The rendering process goes through a graphics pipeline during which the vertices of a triangle are transformed according to the current point-of-view and then projected from world space onto screen space according to the viewing frustum. The point-of-view determines the position and direction from which the world is rendered, while the viewing frustum determines the scope of the field-of-view (FOV).
After transformation and projection the triangle is lighted (meaning lighting calculations are performed on it) and clipped (meaning only visible parts are drawn) and then finally drawn to the graphics buffer. A number of approaches can be adopted during the drawing of the triangle, such as wire-frame only, solid, textured and bump-mapped.
Wire-framing only renders the lines connecting polygon vertices, solid renders color information only, texturing uses bitmap or procedural data that is projected onto the polygon, bump-mapping textures the polygon and utilizes some form of shadowing technique that creates a sense of depth to the image.
2.2 Vertex Representation
The triangle vertices used during the graphics pipeline can be represented in a number of ways, the simplest being a triangle-list. A triangle-list simply stores the vertices in sets of three, corresponding
Perhaps I missed "Graphics Algorithms 101" in a previous /. article, but after reading (or trying to read) TFA my response is: wibble.
John.
for (int x = 0; x 320;x++) for (int y = 0; x 249; y++) drawpixel(x,y,data[x,y]) What ever happened to the simpler times...
je suis parce que j'aime
I hate when something is called a refresher course when it's something I never learned to begin with...
Matt Fahrenbacher
James Tiberius Kirk: "Spock, the women on your planet are logical. No other planet in the galaxy can make that claim."
They for the TNA Algorithm - Tactile Natural Assimilation, for realistic representation of the skin around a woman's Breasts and Backside. This is the money maker, used for everything from Tomb Raider (Lara Croft) to Mario's bulbous (read: breastlike) nose in the popular Super Mario Bros. games.
An egregious ommision.
They have a show for this now, "Trading Mesh Algorithms with Pseudo-fractal Post-processing" or TMAWPFPP for short.
Will they use quadratic?
Who knows!?!
Pure excitement...
This is the first graphics programming article I've seen in a long time with no visual aids. I think the writer simply wanted to write a huge "smart" article so that he'd seem impressive. Missed some good algorithms for terrain rendering (tilemap, octrees, frustrum culling). If you want a really good site about graphics algorithms, check out Paul Debevec's homepage (famous for his contributions to The Matrix)
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I'd rather be flamed than ignored.
Holy?
(I am a Game Developer) and I'm trying to work out why this article was posted. Its too advanced for beginners, its not detailed enough for professionals. Its basically a list of the names & very basic approaches of a few graphics algorithms. I suppose people vaguely interested who know the basics but haven't tried some of these out are the target audience.
Anyone there fit the bill? Did you like this article? Was it helpful and informative?
Game dev and music blog
Yeah, but since it was a version I downloaded from Nintendo.com, I have to periodically spray for pokemon.
Don't blame Durga. I voted for Centauri.
This is a very hot technical issue in gaming right now. The last 5 years have netted us decent techniques for doing network communications for low-latency gaming; with those in place now, we turn again to graphics.
Tribes and Tribes 2 were some of the first games to take on outdoor environments and do them well. Now, we have Unreal Tournament 2004 and Far Cry leading the pack with gloriously realistic outdoor playspaces.
It's only a matter of time before next generation gaming engines like these turn to non-linear gameplay such as what's in GTA 3 and we wind up with a world simulation that has a level of realism approaching reality.
Back in the day, I had a game on my Amiga called "Shadow of the Third moon", a space flight sim, that used voxels. It was quite a novelty at the time and I only had 16MB RAM.
Now that even cheap 3D cards have 128MB RAM on them, average systems have 256MB RAM, where are voxels used now?
google for voxels
This is one of the best collections of graphics algorithms on the net I'm aware of:
comp.graphics.algorithms FAQ
Another favorite of mine is Ray Tracing News, but there haven't been any new issues in a few years.
What other people's favorite collections of algorithms?
-jim
This stuff isn't advanced, it's basic. It's more a refresher course on fundamental methods of organizing scenes. There's nothing difficult or amazing about portals, for example. In fact, much of the tech outlined in the article is outdated. Portals and BSPs (for rendering, not collision detection) are of much less use than they used to be. This quote shows that the author is just reiterating Quake-era views and hasn't written a modern renderer: "BSP trees are supremely efficient in rendering indoor environments." This is completely wrong. On a modern graphics card, it's much faster to throw the scene at the GPU and it let it render it all than it is to iterate through a BSP. Much faster.
There was not a single illustration in the article. That is kind of ridiculous.
This article is like the 10,000,000-foot view of these things.
I used to work for a voxel rendering company, Voxar. I developed the fastest software voxel rendering algorithm for opaque surface rendering of its time, around ten years ago. It wasn't used in games - and still isn't - because it'll always be a performance loser for gaming applications for as long as PCs include dedicated polygon hardware.
Comanche Maximum Overkill does not use voxels. I don't know why they chose that word to refer to the heightfields they do use.
Xenu loves you!
All current graphics accelerators that I am aware of don't do voxels. They start with polygons, apply transforms to those, apply textures, lighting and such, and then rasterize that to pixels. Well since they don't support voxels, a voxel based game would probably just suck. Graphics cards way outstrip CPUs in terms of crunching power because they are specialised for what they do. However that means that if you don't do things the way they want, they aren't useful and you are back to pure CPU processing.
No one is going to be able to market a blocky looking voxel game next to stuff like FarCry and Half Life 2. Even if the voxel engine is "technically" superior, it's not going to matter because lacking hardware acceleration, the end result will be far less impressive.
Heya :)
;)
;) - hence the somewhat formal and academic style; however, in its current form as an article on DevMaster it is intended for intermediate readers. Those that look for some additional insight into (spatial) graphics algorithms. The article isn't a tutorial and (given its history) is not bothered with technical details, however, it does make reference to useful starting places for those that wish to explore the matter some more.
;) Those that really need them should go to the website.
I'm the author of the article. So I guess I can explain a few things.
Originally the article was written 3 years ago as a technical report for a small course I needed to do. DevMaster found this work and asked me whether they could make it available.
The course took place over 8 weeks, covering each algorithm in a week - and 2 weeks for the report at the end. The actual course work is still accessable at
http://www.cs.sun.ac.za/~henri/advgfx.html
And includes pictures and sources to keep everybody happy.
To those that are uncertain who the intended target audience is - well, originally my supervisor...
Although I agree - pretty pics would've been nice.
The choice of algorithms reflects not the state-of-the-art, nor the best approaches to solving graphics issues. The algorithms were, however, easily accessable to me at the time - and hence featured in my one-algorithm-a-week plan.
Somebody mentioned that BSPs are outdated, this isn't true - though they have been around for ages, they are still the work-horse for most indoor engines around. Sure, BSPs are rarely used for the actual rendering process (as mentioned in the article), but in terms of processability of spatial organization they are hard to beat.
I stand to be corrected but I'm rather sure Doom3 makes use of some form of BSPs as well. That should be good enough for anybody.
Lame joke after lame joke, modded higher than you think they should be. Welcome to Slashdot, newbie!
Don't blame Durga. I voted for Centauri.
I make part of my living from commercial sale of scientific visualization software. It performs in software what used to require a $20,000 special-purpose instrument using embedded DSP processors (ouch, more buzzwords). The software is locked into Windows because it uses 1) CreateDIBSection() to allow direct manipulation of pixels in the manner of the post to which I was responding, 2) ScrollWindowEx() so the display can be scrolled using video card hardware, requiring the software to only redraw a small portion with each update, and 3) IDirectDraw::WaitForVerticalBlank() to synchronize scrolls and redraws with the vertical retrace for tear-free video.
Those three calls in Windows came about because Microsoft was trying to wean game developers away from DOS, where the direct control of copying pixel values into a video frame buffer was highly valued. Those three calls were to make 2-D games possible under Windows; those calls also happened to make my data visualization software possible.
There is almost but not quite like it in Java 2D. The direct manipulation of pixels is performed using multiple layers of objects pretty much according to the buzzword pipeline layed out in my original post. The vertical retrace synchronization is also there in some or another BufferManager object, but how it works on different OS's is anyone's guess. The hardware assisted scroll is not there, but hey, everyone is supposed to have such fast computers and video cards.
I was also commenting on 3-D techniques. You got me on that one because I don't have a clue as to 3-D techniques apart from the buzzwords, but it seems I am going to have to learn the 3-D techniques because no one makes 2-D games anymore. My data display goes back some 50 years when it was implemented using hardware filters and thermal paper, and that type of data display will probably be the standard in another 50 years, and I am going to have to figure out how to implement when no one supports 2-D graphics anymore (i.e. pixel-raster displays -- first "they" wouldn't let us touch the frame buffer because that was "too device dependent" and now "they" -- Microsoft with Longhorn, but others will follow -- won't let us touch individual pixels any more).
As software comes up with more advanced abstractions to separate software from specific hardware, it becomes increasingly hard to do interesting things apart from those things anticipated by the abstractions. I was seconding the view of the post to which I was responding that capabilities to do certain things will become lost.