RE: [Algorithms] speed calculations!

[Martin F. <mf...@ac...>]

Work out exactly how far 1 world unit is in your 'universe'. In your case 25
meters == 1 unit in world space. (Which IMHO is quite large)
Assuming 1 second in your game is 1 second of realtime (always useful but
not always true, bullet time etc..)
You'll most likely need a frame compensation value, very few games /
graphics apps get away without one.
 
At 60fps with a movement rate of 1unit per second you want to move 1 / 60 of
a unit per frame. Of course the framerate usually varies, particularly on a
PC if you opt not to wait on the vertical sync. The higher precision timer
you can lay your hands on the better, 
 
So in general
 
Position = Direction * Speed * FrameCompensation;
 
You want your car to travel at 50km/h,
Convert to world units. That's 50,000 / 25 = 2,000 world units per hour
Convert to movement per second 2000 / (60 * 60) =  0.5555556 world units per
second.
 
Multiply this by your frame compensation (1 / 60 whatever) and with the
correct scale of car mesh it should look like you're doing 50km/h. 
 
I would suggest if I may that while you terrain is huge the resolution is
very low, in order to get a good sensation of speed you need detail,
geometric and or texture. 
 
Hope this is of help,
Cheers,
Martin

-----Original Message-----
From: vic [mailto:lo...@cl...]
Sent: 27 March 2001 17:16
To: gda...@li...
Subject: [Algorithms] speed calculations!


Hi,
Here's something i've been wondering for sometime..
How can i make a model move on a world with the speed i want? (in
kilometers)
currently i have a heightmap of size 256x256
i scale the map with the given value (eg. 25 meters per grid unit)
 
int index=0;

for(j=0; j<height; j++)
{
    for(i=0; i<width; i++)
    { 
        vertices[index].x = i * stepSize;
        vertices[index].y = terrain_heights[index] * heightScale;

        vertices[index].z = j * stepSize;
        index++;
    }
}
 
This is how i scale the map. uhm...i wonder... if i want to move a car over
the map with a speed of 50km/h, how do i do it?
saying that each unit (pixel) is one meter scaled by 25, means each unit is
now 25 meters, means: 256*25 = size of the world in  meters, correct?
Anyway, back to the original question.. 
How can i control the velocity of a player over the map, taking in account
the "real" size of the world (in this case 6.400 meters = 6.4km^2  map)?
Cheers,
Vic