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RPC Parking Lot Cars™ 
Copyright ArchVision What's an RPC? Here is a quick introduction to RPC content for those of you that may not have had the opportunity give ArchVision's products a test drive. RPC stands for Rich Photorealistic Content and is in it's basic form, a collection of image assets that can be easily integrated into your scenes. Traditionally, users have used basic geometry planes and assigned a bitmap to that plane to define cars, people, plants, etc. in their scene. The biggest problem with this method was how view dependant each texture was and how time consuming placing these textures could be to ensure a proper match to the perspective, and if you wanted to do an animation you were limited even further. ArchVision has upped the bar by creating a solution that integrates a powerful, but simple user interface, geometry and textures. Where RPC content differs from simple geometry planes is the fact that the texture that get's applied to the plane, or simple geometry in the case of vehicles, are tied to the camera angle. As you move the camera around your RPC placeholder, it is replaced with the proper texture for that camera angle at render time. You simple place a placeholder and the RPC plugin takes care of the rest. RPC Parking Lot Cars™ As I eluded to earlier, RPC Parking Lot™ cars are a bit different from earlier standard ArchVision vehicle collections. The cars created in these earlier collections are meant for use in relatively close up shots or in scenes where you do not have many vehicles in your shots, or where you need advanced functionality for animations. The reason for this is due to the intelligence that is built into these original collections. Things like view dependant specular reflections, turning and rotating wheels for animations, and high res textures that vary depending upon your view and the particular vehicle in the scene. Parking Lot Cars have been scaled back slightly to accommodate a more liberal use of these assets in your scenes. More specifically parking lots. There is really no need to have so much functionality in each model if all it is going to do is sit stationary in a lot of other cars. Parking Lot Cars Volume 1 is a collection of 16 cars that includes: Acura RSX, Audi A6, Audi TT, Cadillac DeVille, Chrysler PT Cruiser, Chrysler Voyager, Ford Econoline, Ford Focus, Honda Civic, Mercedes Benz C Class, Nissan 350Z, Saturn Coupe, Saturn Vue, Subaru Impreza, VW Beetle, and the VW Phaeton. 
RPC Parking Lot Cars Volume 1 Collection Each car uses one set of textures per car, regardless of the view from which they are being observed, that are a lower resolution that those found in the standard automobile line up. Also the base geometry of theses cars is quite a bit smaller than the standard cars as well. This both reduces memory consumption and the time your scene will take to render and prepare. It is worth mentioning at this point that when I say geometry this is really something that happens behind the scenes. Although you simply position a place holder in your scene, regardless of the Automobile collection you are using; at rendertime a simple geometric model and textures are rendered quite transparently to the user. According to Randall Stevens, President of ArchVision, the polygonal hulls used by the Parking Lot cars are some 1800-3000 polys smaller than their full featured counterparts, which range from 3-4K polys each depending on the model. Each of the textures in the RPC Parking Lot Cars™ collection range in size from 1.5Mb to 2 Mb per car. How do they stack up? While there is not a lot that can be tested and examined with this collection, I did want to test the two areas that everyone will be asking about: "how close can I get before the textures fall apart?" and "how many cars can I place in my scene and still have it render in a decent amount of time?" First, let's take a look at close up we can get. Below, I have rendered out 4 detail shots of varying distances. As you can see, you have to get up pretty close before the realism starts to deteriorate. I was pleasantly surprised by the ability of the cars to hold their own and it clearly show that you should be able to use this collection in a wide variety of situations. 
To cover the second question of how many cars you can realistically place in a scene, I discovered that this is a bit more complex a question than I had originally thought. I contacted Randall Stevens again to help clarify and explain exactly what goes on behind the scenes when you use this collection. I was told that each vehicle texture in your scene is loaded only once, regardless of how many instances of that vehicle are placed. So even if you position 50 Audi TTs in your scene, the texture for that car is loaded but once. However, the geometry hull that is also loaded, is not instanced but rather inserted uniquely each time that model is inserted. This is where adding too many cars could affect your overall frame render times. While it should not prove to be too much of a problem for most people's scenes, it could cause very long frame preparation times if you place too many. I have been told that geometry instancing is something that is already being addressed for a future release of the RPC-Plugin that controls all of the RPC data. So that having been said, how many cars can you place? Well I ran 4 tests, one with 100 cars, 200 cars, 500 cars and 1000 cars. As there are really two components to the time each frame can take, I divided my test times into two sections. The total time it took to prepare the frame and the time it took to render the frame both raytraced and with shadow maps. The results of the test are below:
All tests were done on a Dual Athlon 1900+ with 2GB of RAM at 640 x480 using default shadow map and raytrace settings. 
1000 ArchVision Parking Lot Cars. As you can see, 90% of your frame time is attributed to the preparation of the RPC data, while the actual rendering time is quite trivial in comparison. You can really see where the performance takes a slide when you add over 500 cars to your scene. Although having rendered that many cars I can't not honestly say there would be too many scenarios where one should ever need to place that many cars in one scene. You should also consider that placing 1000 cars in your scene adds close to a million polygons, so it's not that surprising that the render times do increase quite dramatically. 
Copyright ArchVision  Copyright ArchVision  Copyright ArchVision Copyright ArchVision
From an esthetic point of view I was quite happy overall with this
collection. The vehicle makes are pretty average to what you would
expect to find in a typical North American parking lot and the cars
are not vibrant sports car colors that stand out like a sore thumb
in your scene. There is also enough variation in both make and color
that it's pretty tough to see repeats in your scene unless you were
really looking. The only drawback I can see is for the European
and foreign markets. This collection is comprised of 90% North American
makes so may or may not be suitable for an overseas application.
However, based upon the fact that this is volume 1, I would assume
that more models will be introduced soon. For more information about ArchVision and the RPC™ Parking Lots Cars™, please visit: http://www.archvision.com If
you would like to post comments or questions about this review,
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