Lock Old Threads [Lock Old Threads]

Christopher Hawkins — Sat, 07 Mar 2009 03:14:52 GMT

Threads should be locked after thirty days of inactivity or some similar interval. This would curb the inordinate amount of Necroposting on C9 (especially in the Tech Off).

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Generating a Prism from a Polygon in XNA [Generating a Prism from a Polygon in XNA]

Christopher Hawkins — Mon, 17 Nov 2008 09:33:08 GMT

Apologies. Double post. Channel9 gave a non-descript error message several times when I tried to post the original and edit this duplicate.

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Generating a Prism from a Polygon in XNA [Generating a Prism from a Polygon in XNA]

Christopher Hawkins — Mon, 17 Nov 2008 09:32:38 GMT

I'm working on a project for a client, and this has been really bugging me. I'm not quite mathematical enough to solve this problem by myself and I desperately need some insight. I'm vainly attempting to generate three-dimensional prisms in XNA for the display of cabinets. So far, I've got the following code but it does not draw properly at all. I know the actual draw code is correct as it works for other shapes, so it's the vertex and index buffers that are wrong.

If anyone can point to a sample or something I'd be incredibly grateful. So far, everything I've got I've derived from my limited knowledge of three dimensional mathematics.

My current, and non-functioning, solution is a constructor method (don't worry about the length, I'll refactor it later) taking an array of Vector2s as the outline of the polygon to extrude into a prism and a Vector3 that represents the centre of the prism (thus giving it depth and direction).

Currently I:

Create a rotation matrix by concatenating three matrices constructed using the angle derived from the dot product of the prismVector and the three cardinal axis
Use this to transform the 2D vertices into 3D and subsequently create the bottom by subtracting prismVector
Here the problems start (I know they're not above because I've simplified most of that out at the moment)

Generate the caps of the prism:

            //CAPS:

            // prism vector will be 0 in the vertex array
            for (int i = 1; i

Generate the sides:
```
            for (int i = 1; i 
```

Add all vertices

            Vector3 topNormal = Vector3.Normalize(prismVector);
            Vertices.Add(createVertex(prismVector, topNormal));

            for (int i = 0; i

I'm in way over my head with this project. Of course I don't expect anyone to actually read all that and come up with a solution, but I'm sure this is something that people have had to do a million times before and I'm absolutely confused as to why I can't find anything with Google (maybe I'm searching for the wrong thing…).

If you know of any samples or have ever had to do anything like this before, please help.

Cheers,
Chris

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Lock Old Threads [Lock Old Threads]

Generating a Prism from a Polygon in XNA [Generating a Prism from a Polygon in XNA]

Generating a Prism from a Polygon in XNA [Generating a Prism from a Polygon in XNA]