Hello

I know I'm a prick...but can somebody help me with this (it takes too long for me to translate into c-script ) :

I have a river and would like to calculate the stream-force direction according to the rivers vertices (the vertices are setup like 1,3,5,7,9...). Now when my boat is at vertex#1 position, the stream-force direction should point towards vertex#3 position...and so on.

I'd be very glad for a snippet that manages this

Thanks!

ok, here's an idea...

If it indeed is all in the correct order (1-2, 3-4, 5-6, 7-8 etc etc), you could calculate the distance and rotation.

first you set a temp variable at the current vertex.
then you calculate the distance from the boat to the next vertex, and check if that distance is shorter then the current one, if so, the next is the current one.

then you can use the current and next one to calculate a rotation angle.
after doing that, you can also speed up / slow down the boat using the distance between these 2 vertices...

i am at work atm, cant test/write any code, but it's a general idea.
I'll check later what i can do, can you upload the river model somewhere?

regards,

Hey thanks for your fast input...your idea sounds cool!

Here's the river model

Hi,

you can use c_trace to get the closest vertex to your boat. 'hitvertex' will be set to its number.

Then you could determine if the vertex number is even or uneven to get the correct vertex pair. However you only need this, if the broadness of your river varies. In this case you need to get a direction vector from one vertex pair to the following vertex pair. A 'vertex-to-vertex' direction vector could result in a inapplicable direction.

You can determine if a number is even by using something like the following function:

function even(_n) {
// returns 1 if _n is even, otherwise 0
return(_n % 2 == 0);
}

To get the direction vector from one pair to the next pair you would have something like this:

------
// get the position of the closest vertex pair

vec_for_vertex(temp, river, closest_vertex); // get the vector of the closest vertex
vec_for_vertex(temp2, river, closest_vertex - (2 * even(closest_vertex) - 1); // get the vector of the adjacent vertex

vec_add(temp, temp2);
vec_scale(temp, 0.5);
vec_set(pair1, temp); // pair1 = origin of the vertex pair

// get the position of the next vertex pair

vec_for_vertex(temp, river, closest_vertex + 2); // get the vector of the next vertex
vec_for_vertex(temp2, river, closest_vertex - (2 * even(closest_vertex + 2) - 1); // get the vector of the adjacent vertex

vec_add(temp, temp2);
vec_scale(temp, 0.5);
vec_set(pair2, temp); // pair2 = origin of the vertex pair

// finally get the direction vector

vec_diff(speed_vector, pair2, pair1);
------


This is a sloppy written code and I don't know if it actually works. ;-)

Thanks Fenriswolf! Sound usefull too. Is there a way to avoid the c_scan??

Instead of using c_trace you could also use vec_dist to calculate which is the closest vertex to your boat.

You can do this thusly:

------
var closest_vertex; // number of closest vertex
var closest_vertex_distance; // distance of closest vertex
var i;

i = ent_vertices(river_entity);
vertex_distance = 999999; // initializing with highest possible value

while(i > 0) {
vec_for_vertex(temp, river_entity, i);

var vertex_distance;
vertex_distance = vec_dist(boat_entity.x, temp);

if (vertex_distance < closest_vertex_distance) { // if this is the closest vertex, save it
closest_vertex_distance = vertex_distance;
closest_vertex = i;
}
i -= 1;
}

// at this point closest_vertex stores the number of the closest vertex to the boat
------

Of course you can put this code into a function to make it universally applicable.