Getting correct quad(patch) camera is over

If I understand you right, you need to get the Y-position of the point you are currently standing on so that you could follow the terrain, right ?

So you have the X and Z coordinate (P.x, P.z) of point P, now:
1. Find out which triangle of the quad are you standing on (compare X,Z coords of the quad`s points)
2. Since you have heightmap with regular distances between points, the situation looks like this:

T3
|..
|...
|....
|.....
M1-P--M2
|.......
|........
T1-------T2

T1,T2,T3 - points of the triangle you are standing over
P - your position over terrain inside the triangle
M1,M2 - line that is paraller with line T1,T2
3. You can find the P.y from the line equation of line M1M2
4. You calculate M1 from line equation of line T1T3, where M1.x = T1.x, M1.z = P.z
5. You calculate M2 from line equation of line T2T3, where M2.z = P.z , M2.x - calc.it from 2D line equation T2T3, the same with M2.y but now from 3d line equation
6. Just calculate P.y from line equation M1M2, knowing P.x and P.z

Where I mention "line equation" I mean simple interpolation with deltaX, deltaY, deltaZ.

It is not the only way, nor the fastest, but i think it is most obvious and simple.

VladR
Avenger game


[edited by - VladR on May 23, 2003 3:02:32 AM]

Thanks for your help VladR,

Kind regards,
Steve