Basic basic - What is a pologon?

[raymar 969]

s/b PolygonAs my wife was driving the car and I was reading a quick print pdf of my latest super airport scenery, I read this out loud - "This scenery package contains more than 2 million polygons". She stopped me with a simple question - What is a polygon in that context? Duh. Help me out guys and girls? How should I have answered her simple question? Besides being good looking, she is way brighter than me so it also needs to make sense to someone who knows nothing about fs scenery designing. :( Ray

[Chock 17,769]

Each object in FS uses vector-based polygons, which then have textures mapped onto their surfaces to make them look like buildings, aeroplanes etc.If you imagine a simple cube, that would have eight points, defined in 3D space as coordinates, to create it (one at each corner), those eight points, can be joined together with lines, which is why it is called a vector-based polygon, because each one of the lines sets off (on a vector) from one point in 3D space to another point in 3D space to join them up. When all the corner points on a cube are joined up with lines, you have a wireframe polygon (i.e. there are no sides to your cube, just the basic wire frame shape). Since each side of a wireframe box has four vector lines joining it up to make a square side of your box, it is possible to define that space as a flat plane (i.e. make it a side of the box). When you have a flat plane (side of the box), you can then 'map' a texture to it by telling an image to display on that surface, based on giving it coordinates.Your imaginary box will have six such flat planes (like a die has six sides). This makes it 'a six-sided polygon'. When 3D designers talk about how many polygons a model has, this is what they mean, i.e. a cube has 'six polygons', so an airport scenery might have several hundred buildings made from all kinds of differently shaped polygons, but they will all be created using the above method, and it is however many sides all those boxes, cylinders, prisms etc that were used to create the scenery that amount to how many polygons the entire model has.Al

[PingPong 60]

Awesome explanation Al, I guess I just realized I didn't know that myself.

[raymar 969]

Each object in FS uses vector-based polygons, which then have textures mapped onto their surfaces to make them look like buildings, aeroplanes etc.If you imagine a simple cube, that would have eight points, defined in 3D space as coordinates, to create it (one at each corner), those eight points, can be joined together with lines, which is why it is called a vector-based polygon, because each one of the lines sets off (on a vector) from one point in 3D space to another point in 3D space to join them up. When all the corner points on a cube are joined up with lines, you have a wireframe polygon (i.e. there are no sides to your cube, just the basic wire frame shape). Since each side of a wireframe box has four vector lines joining it up to make a square side of your box, it is possible to define that space as a flat plane (i.e. make it a side of the box). When you have a flat plane (side of the box), you can then 'map' a texture to it by telling an image to display on that surface, based on giving it coordinates.Your imaginary box will have six such flat planes (like a die has six sides). This makes it 'a six-sided polygon'. When 3D designers talk about how many polygons a model has, this is what they mean, i.e. a cube has 'six polygons', so an airport scenery might have several hundred buildings made from all kinds of differently shaped polygons, but they will all be created using the above method, and it is however many sides all those boxes, cylinders, prisms etc that were used to create the scenery that amount to how many polygons the entire model has.Al

Sir Chock,Good answer. She sat down at my pc and read it and says thank you very much and she is sorry about your crappy weekend in Londontown. :( Ray

[Chock 17,769]

Of course the quicker and more entertaining answer is to say that a polygon is a dead parrot.If you are curious about how it all works, download this free program and check out the video tutorials also at this link. You could be knocking up polygons in minutes with this thing, as it is very easy to learn:http://sketchup.google.com/If you are feeling more adventurous and actually you want to make stuff for FS, I recommend FS Design Studio by Abacus. You could be up and running in an afternoon with that if you did the tutorials, and you can make anything you like with it, including aeroplanes. And don't be put off by the fact that Abacus make it, it's an excellent piece of software:http://www.abacuspub.com/default_fs.htmlAl

[CoolP 283]

Of course the quicker and more entertaining answer is to say that a polygon is a dead parrot.

:LMAO:Ok, now I've come to the point that I request a dedicated Alan B. Show, hosted at Avsim.Users can drop in any question and watch the outcome.Any supporters?

[Guest jahman]

Each object in FS uses vector-based polygons, which then have textures mapped onto their surfaces to make them look like buildings, aeroplanes etc.If you imagine a simple cube, that would have eight points, defined in 3D space as coordinates, to create it (one at each corner), those eight points, can be joined together with lines, which is why it is called a vector-based polygon, because each one of the lines sets off (on a vector) from one point in 3D space to another point in 3D space to join them up. When all the corner points on a cube are joined up with lines, you have a wireframe polygon (i.e. there are no sides to your cube, just the basic wire frame shape). Since each side of a wireframe box has four vector lines joining it up to make a square side of your box, it is possible to define that space as a flat plane (i.e. make it a side of the box). When you have a flat plane (side of the box), you can then 'map' a texture to it by telling an image to display on that surface, based on giving it coordinates.Your imaginary box will have six such flat planes (like a die has six sides). This makes it 'a six-sided polygon'. When 3D designers talk about how many polygons a model has, this is what they mean, i.e. a cube has 'six polygons', so an airport scenery might have several hundred buildings made from all kinds of differently shaped polygons, but they will all be created using the above method, and it is however many sides all those boxes, cylinders, prisms etc that were used to create the scenery that amount to how many polygons the entire model has.Al

The die is a good example, but let me clarify in the case of the die the eight vertices in space define a wire-frame solid consisting of six flat polygons (one polygon for each face of the die), where each of the six polygons is a four-sided polygon.In practice all polygons are three-sided, i.e. triangles. The vertices (singular: vertex) are used to "track" (sample) a 3D curved surface (scenery or aircraft) to decompose that surface into its underlying polygons, in a 3D analog-to-digital conversion very similar to the 2D analog to digital conversion of sound (used to be mostly music in the good old days) whereby a 2D curve (think "sine wave") is converted into a series of bars with height approximating the sine wave.Then as chock explained, those individual polygons (triangles) are covered with textures (aircraft bitmaps or scenery ground textures or photo-real textures), all polygons hidden from view given the observer's point-of-view are removed so they are not rendered on-screen (or brightness is reduced if the obscuring polygons are translucent as in the case of a windscreen, clouds or haze), then lighting is applied to lighten or darken each polygon according to angle to the light source and to the viewer, and then these calculations are all repeated 30 times per second (the frame rate) accross the 2.28 million individual pixels on a 1900 x 1200 screen, while at the same time loading new scenery polygons and textures as the aircraft moves along.Complex aircraft models like the PMDG B-744 have in the order of 0.25 million polygons with 0.75 million vertices that are rendered at 30 FPS. Its actually nothing sort of amazing...Flipper shows-off his polygons (notice effect of lighting):Cheers,- jahman.

[spotlope 0]

I think a lot of devs (or at least a lot of their press releases) confuse polygons with triangles. As was said above, the basic unit required to display a 3-D object is a triangle - three points in space (vertices) that are connected to form a flat shape. A polygon can be made up of many triangles, but the triangle is the simplest root object that will actually show up in FS.By the way, saying something has two million polygons is a dubious brag in the context of a real-time game like FS. The goal is to use as few of those precious triangles as possible while maintaining the illusion of reality, lest we bring the poor computer to its knees trying to display them all. My proudest moments as a modeler are when I use a handful of triangles to represent something that looks real.

[Chock 17,769]

Incidentally, the above clarification is indeed correct, although I thought it best not to confuse matters by getting into the whole triangles bit!Of course the real skill in making a model comes with knowing what you will have to physically model and what you can get away with simply by using textures, since the less polygons you have to shift about, the quicker things actually will shift about.A recent example of that where I blagged a shape with textures was a Ray's beloved P-8 Poseidon repaint of the iFly 737 NG that I did, where I added the extra avionics housings purely with textures by painting fake areas of light and shade since they were not really present as polygons on the model of a basic 737.There is a limit to what you can do with that technique of course, but it does show that it can be fairly convincing on a model that is a simpler shape.Here's an example of a pretty low-poly model of the pilot on my DH-9 model. The head is basically a sphere with a nose shape extruded from it; all the shape is really from the textures that are mapped to it, fooling us into thinking the shape is more detailed than it really is:Al