[filax] TerraED Pro

Make Freelook and you see: It is not a bug. This is a feature!

hmpf. okay

double Interpolate (double fA, double fB, double fX)
{
	return (fA * (1 - fX) + fB * fX);
}

double GetHeight (double fx, double fy)
{
	if (fx < 0 || fx > WIDTH)
		return 0.0; // ERROR!


	if (fy < 0 || fy > HEIGHT)
		return 0.0; // ERROR!


	int x = (int) fx;
	int y = (int) fy;

	int x1 = x + 1;
	int y1 = y + 1;

	double dX = fx - (double) x;
	double dY = fy - (double) y;

	double fHeight1 = m_afHeightmap[x + y * WIDTH];
	double fHeight2 = m_afHeightmap[x1 + y * WIDTH];
	double fHeight3 = m_afHeightmap[x + y * WIDTH];
	double fHeight4 = m_afHeightmap[x1 + y1 * WIDTH];

	return Interpolate (Interpolate (fHeight1, fHeight2, dX),
						Interpolate (fHeight3, fHeight4, dX),
						dY);
}

This works like this:

Actual_Height_On_Actual_Camera_Position = Interpolated 1-, 2- 3, or 4- terrain-vertex-height in position of the camera.

If Camera_Y > Actual_Height_On_Actual_Camera_Position Then
... oh my god ...
End If


Here is more information for you: http://www.gamedev.net/community/forums/topic.asp?topic_id=205690


Edit: I think its only fair for posting a optimized sample, too.

//------------------------------------------------------------

//

// example

// -------

//

//      (x0, h0, y0)       (x1, h1, y0)

//          +---------------+         

//          |             ./|         

//          |           . / |         

//          |         .  /  |dy       

//          |       .   /   |         

//          |     .    /    |         

//          |   .     +-----+          ^

//          | .        dx   | (1-dy)   |d_hy =(1-dy)(h1 - h3)

//          +---------------+          v

//     (x0, h2, y1)       (x1, h3, y1)

//

//                     <--->

//                       d_hx = dx(h2-h3)

//

//

//   h = h3 + hx + hy

//

//------------------------------------------------------------


double GetHeight (double fx, double fy)
{	if (fx < 0 || fx > (WIDTH - 1))
		return 0.0; // ERROR!

	if (fy < 0 || fy > (HEIGHT - 1))
		return 0.0; // ERROR!

	int x0 = (int) fx;
	int y0 = (int) fy;
	int x1 = x0 + 1;
	int y1 = y0 + 1;
	double dX = (double) x1 - fx;
	double dY = fy - (double) y0;
	double h0 = g_afHeightMap[x0 + y0 * WIDTH];
	double h1 = g_afHeightMap[x1 + y0 * WIDTH];
	double h2 = g_afHeightMap[x0 + y1 * WIDTH];
	double h3 = g_afHeightMap[x1 + y1 * WIDTH];

 	double h;
	// top left triangle

	// interpolate with origin at (x0), and going towards

	// x1 and x2

	if (dx > dy)
	{
		h = h0 + (1 - dx) * (h1 - h0) + dy * (h2 - h0);
	}
	// bottom right triangle

	// interpolate with origin at (x3), and going towards

	// x2 and x1

	else
	{
		h = h3 + dx * (h3 - h2) + (1 - dy) * (h1 - h3);
	}
	return h;
}