# HUD algorithms for glass HUD/MFD window

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Folks,

Does anyone know any HUD algorithms like pitch ladder, compass tape, direction, velocity vector, etc for writing flight simulators? I was looking for them through google and books but did not found information so much. That's why I am looking for OpenGL-based HUD drawing routines for glass HUD display and MFD window.

Thanks,

Tim Stark

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Just figure out what the elements you want are, and design them out on paper, and start working out how to generate shapes that depict that. A compass tape, for instance. You want vertical lines, of varying heights. Assume model-space 0,0 is the center of the tape, take as input the bearing and desired width (in degrees) to include notches for and let some parent function deal with the position and size of the tape on the HUD (by setting the modelview matrix appropriately).

You'll want to use the the fractional part of the bearing as a horizontal bias for the notches, and then generate several notch lines left and right of center, all of them offset by the bias. If you use integer modulo tests to determine whether to use a short or tall notch, you should probably add 360 to your bearing first, because most languages' modulo operator doesn't treat negative numbers correctly.

If you do it right, it should be configurable and controllable by *any* simulated data. You should be able to make a test viewer where you set the "flight" parameters in a GUI form using text boxes and numeric sliders, and see the resulting HUD rendered, without any simulated airplane ever being involved.

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There is no one true algorithm for any of these. It's also not too complicated to implement.

Compass tape is dependent on the facing direction of the camera or plane along the X,Z plane. Doing a bit of vector math after projecting to that plane will do the trick. This requires you to determine which facing direction is North, East, South, and West. And then interpolate between these distances.

Velocity Vector is more dependent on the computations from the CPU than the GPU. I'm not going to explain this, because there's literally thousands of different styles to this. I can't guess at what you want.

I don't know what you mean by a "Glass" hud. I guess you mean that holographic style where they appear in a see through crystal? If so, then it's two different options. Both of them are about the same. You can render the hud directly to the glass, but it doesn't give you that temporal effect. Or you could try rendering it to a cube map.

Edited by Tangletail

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