April 2005 Archives

The latest source for Nogredex is now in the Ogre Sorceforge CVS repository

I've also uploaded a stand-alone demo of Nogredex, you can get it here

I've removed the 16 bit index limitation on meshes. You should now be able to load any size mesh you want. (I wouldn't recommend it tho, in my testing I found that Novodex starts to bog down on meshes larger than 10,000 triangles).

Meshes with more than one sub-mesh are now fully supported and correctly simulated. I've also added some optional code that will even optimize these types of meshes by removing duplicate vertices.

Enjoy!

WinCVS 2.0

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WinCVS 2.0

...is now official. 2.0 includes built-in support for CVS over SSH... go get it.. :)



As promised, I've added arbitrary mesh support for Nogredex, the Novodex + Ogre framework. As usual, this is open source code so I would appreciate peer review if you have any comments or suggestions.
Generate your own scientific paper

Looks like I'll have no problem writing my thesis now!

Some of the references in their example paper are hilarious: Proceedings of the Workshop on Bayesian, Amphibious Modalities. LOL. OMG, the stink of geek is pretty high here, watch out!

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New graphics card in the mail

I spent most of last weekend investigating displacement maps and refactoring my terrain code so I would be ready to support DirectX 9 displacement maps, only to discover that my Ti 4600 doesn't support it. D'oh. I guess part of me wasn't listening to the voice of reason.. after all, my card doesn't support anything past vertex/pixel shader 1.1.

I'm bummed about replacing this card because it truely is a fast card. It runs every new game I've tried on it just fine; or at least at a high enough level that it doesn't distract me. I'm bummed because in order to get a card that is superior to it in speed I have to spend at least $110. In the past when I've replaced my video card getting a faster model only meant $50 because technology had been moving so fast. I guess not now.

In today's graphics market it looks like the chip makers are going after features and pipelines over speed. The new cards feature more pipelines, faster memory, etc., but the raw texel fill rates aren't dramatically higher than what was available a year ago.

So my new card is going to be an nVidia 6600 GT, it looks like right now that's the best bang for the buck. I opted to get one of the MSI models, since everyone seems to be saying they're nice and quiet and don't run too hot.

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Surfer fends off shark attack, get's right back on surf board 30m later

Twice I've severely twisted my knees snowboarding, but I didn't let it ruin my day. In retrospect, that was probably a really dumb thing to do. A shark attack is a little different, but I guess if the waves are good you gotta do what you gotta do!

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Graphics device capabilities matrix

This website is a great reference. Plug in a a card that you're considering buying and it'll show you exactly what it does and doesn't support.

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Ported Nogredex to Ogre 1.0.1

I just completed a port of the Nogredex demo to Ogre 1.0.1. Nogredex is a framework for combining the Ogre 3D graphics engine with Novodex, a killer physical simulation library. Novodex + Ogre = nOGREdex. Har har. (I pronounce it NO-gerr-dex).

Nogredex is great because it completely abstracts away the complexity of routinely inspecting the state of your physics state during your draw loop. You just do a Nogredex->addObject() and it does the rest, you never have to deal with the object again (unless you want to, of course).

I've been using Nogredex extensively in my research. I've actually been expanding it to add new object types, new object constructors, etc. Right now I'm working on adding mesh support.

I'd appreciate some peer review of my code, so if you're interested in this sort of thing please check it out.

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Orthoimage overlays



I figured out how to overlay USGS "DOQ" files in geotiff format over my terrain. (What you saw previously was a screen grab of some of their website data hand stretched over the terrain.. hehe). Now I'm actually rendering the real thing, at about 1 meter resolution.

The orthoimage for just the NE portion of the Corvallis quad is about 40mb alone. It takes a few seconds to load this guy. :-)

Overlaying the geotiff files actually isn't that tough. There's an open source library called libgeotiff that does pretty much all of the hard work for you. Since DirectX can only load BMP/JPG files as textures I actually don't even use the .tif file that comes as part of the geotiff file... I convert it to a .bmp and then use libgeotiff to pull out the metadata. Once I have the coordinates of the geotiff in UTM I can easily overlay it onto my height-map, it's just a matter of scaling the coords into the texture coordinate system of the height-map.

Speaking of UTM, I should mention that I encountered some horrible floating point error dealing with UTM coordinates. The coordinates for Corvallis are something like (470187.46959, 4927222.852384). Big numbers. The spacing between heights in the elevation data file are somewhere around 0.00087. Well I can't just go around adding floating point numbers of such different magnitudes together and expect things to work (I tried, heh), so I got around this by translating everything to the origin and working with the elevation and geotiff data in reference to 0,0 instead of those huge UTM coordinates. Everything is still UTM, it's just offset by a lot.

I also downloaded some plant coverage data, part of the "national land cover dataset." This also comes in geotiff format. Next I'm going to look at writing a vertex shader that draws little trees and grass where the land coverage data says they should be.

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Finally, some terrain



I finally got some terrain rendering. Pictured above is the 7.5 minute data for hills just north of Corvallis.

The complete 7.5 minute quad is about 1.3M vertices ~= 2.7M faces. I know this is a lot, but I didn't think that it would be too much for my graphics card to handle (Ti 4600). Apparently it is, because at full-resolution this scene only gets about 1.5fps. If I bump things down by sub-sampling the elevation data at every-other point I get about 8fps, and at every third sample (what you see above) I get about 30fps.

The data comes from USGS SDTS files. I finally bit the bullet and went with SDTS because a) it's the new format (new as in after 1996) and b) it's the only format you can get 7.5 minute data in for free. The USGS doesn't have it on their site, but if you fight hard enough and create a fake registration account you can get it for free from mapmart.com.

I'm parsing the SDTS files using sdts++, an open source package from the USGS. Earlier I complained about sdts++, but after using it some more it ain't so bad. Its one major downfall is its heavy reliance on RTTI and C++ exceptions. For debugging I just compiled it right into my program and ate the performance hit so that I could catch the exceptions. I need to figure out how to segment it into a library so I don't need to have RTTI going in the main app.

Todo: I really want to get some orthoimagery and try and do an overlay. I think that would be badass. Real-time weather data and cloud rendering would be neat too.

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On building sea ferries

"It's exactly the same thing as the Internet, but we're moving butts and boxes instead of bits."

Timothy Dick, chairman of Hawaii Superferry Inc

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USGS Mapping Software: DLGV32

A few years ago, after I bought my GPS, I got into map making and map software. There's a lot of data available for free from the USGS. They don't make it easy to find, but it's out there if you look hard enough.

One of the free viewers of USGS data that was available when I was doing this years ago was DLGV32. DLGV32 was originally written by a USGS employee in the mid-90s. This employee then left the USGS and started selling DLGV32 "Pro" himself. You can find his commercial version of the program online for $219 at GlobalMapper.com.

Since I was last making maps, something must have happened with DLGV32. The "Pro" version is now available from the USGS (link above), along with the source code. I've since become interested in mapping again so I thought I'd try out the source code.

Impressions of the source code:

  • The DLGV32Pro source is dated March 2005 but is built using MSVC++ 6. ???

  • Here's something I've never seen before: debug symbols were explicitly turned off on key files. It took me a while to figure this out.

  • The shipping source available on their website won't compile, it contains trivial typos that prevent it from compiling.


It's as if they want to discourage you from compiling and exploring the source code. Hmm.. could that be because there's a former USGS employee trying to sell a commercial version of the same program??

Footnotes:

There are libraries available to parse USGS map data, like data in the STDS format. One of these is the stds++ library but it's built to compile on the MSVC++ 6 version of STL, which is a mess. I don't feel like bringing it up to VS.NET2003.

The USGS Seamless Data Distribution website is a good place to get vector data, like roads, railroads in DLG and SDTS formats.

MapMart.com has 7.5 minute super high resolution elevation maps available in SDTS format.

The EROS Data Center keeps on their ftp site 1:250,000 scale digital elevation map (DEM) files. 7.5 Minute data is also available, but I can't find a user-friendly index so you have to guess from the file names. DEM is by far the easiest file format to deal with. I've managed to figure out the format myself, but I'm still looking for a good tutorial on how you're officially supposed to deal with the file format. The official specification is amazing verbose while still lacking the essentials necessary to get started parsing the format. A grammar would be a nice start.

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Dance Dance Diet

I think this is the second time I've blogged about this, but it's back in the news again: Dance Dance Revolution as a weight loss program for kids.

I used to be all about DDR, but I can't play it anymore. DDR and snowboarding were major contributors to the downfall of my knees. I'm not sure it's wise to recommend repetitive impact activities like this as part of any exercise program, let alone for weight loss.

Maybe on the lower levels where you're just walking around the pad DDR is OK, but when you get better DDR becomes a double-time, high impact step aerobics routine nightmare. It's a lot of fun, but it's also a lot of jumping and landing at odd angles. If you're already overweight the impact would just become worse I would think.

I've met two other people that also blame DDR for screwing up their knees, especially the arcade version, where you play on a hard surface with shoes on. It's even worse for your knees than the home version.

Long live Stepmania.

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This page is an archive of entries from April 2005 listed from newest to oldest.

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