Hovercraft theory: hovering forces, damping, springs..

Flavien Brebion · 2003-09-28T18:59:56

I''m working on an hovercraft racing game. However i''ve got some problems with my hovercraft. It''s very unstable: as soon as it starts to tilt, it continues to tilt for a long, long time. I want the movement to damp after 1 or 2 seconds. The hovercraft is simulated by a simple oriented bounding box. For the hovering physics, i get the 8 corners of the bounding box in world space, cast a ray under the hovercraft to find, for each corner, the distance to the ground. As a result, i get 8 contact points with the ground, and for each i know at which distance the corresponding corner of the OBB is. I apply a formula (that''s the one causing my problems) mostly based on this distance to generate a force applied at the corner of the hovercraft. Each force results in a bit of linear and angular velocities. I''m not a complete newbie on physics, but not an expert either (i''m using ODE btw). For my formula i tried to implement a damping/spring force based on this: f = (-damping * dp - spring * d) / m; Where damping is the damping coefficient, spring the spring coefficient (how original). dp is the dot product of the velocity and the normal at the ground, generally it''s just the Y component of the velocity. d is the distance to the "target hovering height"; for example if it''s a height of 4.0 above the ground and the current position is 2.5, d = 2.5 - 4.0 = -1.5 The problem i have is that, although it works well in 1D, this formula doesn''t seem to work at all when using 8 springs. It''s as if the effect of one spring was cancelling the effect of its opposite. As a result, my hovercraft hovers at the correct height, but is tilting like mad, and it doesn''t seem to damp at all. I tried many parameters for the damping and spring constants but none seem to work. I can probably provide a video if needed. Any help is welcome. Y.

Math and Physics Programming

Started by Ysaneya September 23, 2003 05:50 PM

9 comments, last by Ysaneya 20 years, 6 months ago

Milamber12345

122

September 28, 2003 06:59 PM

If the camera going through walls is not a problem, just modify your current program to make the camera be positioned based on the previous frame''s position of the hovercraft, instead of the current frame''s position. Still make it look at the current frame''s position, though. This method makes a nice looking effect without any additional computation.

Hovercraft theory: hovering forces, damping, springs..

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Hovercraft theory: hovering forces, damping, springs..

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