Function setRadial

examples/Heightfield/HeightfieldExample.cpp:245–300

creates a radially-varying heightfield

// creates a radially-varying heightfield
static void
setRadial
(
	byte_t * grid,
	int bytesPerElement,
	PHY_ScalarType type,
	btScalar phase = 0.0
)
{
	btAssert(grid);
	btAssert(bytesPerElement > 0);

	// min/max
	btScalar period = 0.5 / s_gridSpacing;
	btScalar floor = 0.0;
	btScalar min_r = 3.0 * btSqrt(s_gridSpacing);
	btScalar magnitude = 5.0 * btSqrt(s_gridSpacing);

	// pick a base_phase such that phase = 0 results in max height
	//   (this way, if you create a heightfield with phase = 0,
	//    you can rely on the min/max heights that result)
	btScalar base_phase = (0.5 * SIMD_PI) - (period * min_r);
	phase += base_phase;

	// center of grid
	btScalar cx = 0.5 * s_gridSize * s_gridSpacing;
	btScalar cy = cx;		// assume square grid
	byte_t * p = grid;
	for (int i = 0; i < s_gridSize; ++i) {
		float x = i * s_gridSpacing;
		for (int j = 0; j < s_gridSize; ++j) {
			float y = j * s_gridSpacing;

			float dx = x - cx;
			float dy = y - cy;

			float r = sqrt((dx * dx) + (dy * dy));

			float z = period;
			if (r < min_r) {
				r = min_r;
			}
			z = (1.0 / r) * sin(period * r + phase);
			if (z > period) {
				z = period;
			}
			else if (z < -period) {
				z = -period;
			}
			z = floor + magnitude * z;

			convertFromFloat(p, z, type);
			p += bytesPerElement;
		}
	}
}