3D positioning

3D positioning#

Goal: place sounds at coordinates in the scene, move the listener through them, and hear the panning and distance attenuation update in real time.

Walks through Demo02_3D, which moves two sounds and the listener around a small console-driven 3D space.

Source: Demo02_3D.cpp.

The Pos class#

Every position in libYSE is a YSE::Pos — a simple struct with public x, y, z floats. Construct one in-place, or use zero() to reset:

void Demo3D::Reset()
{
	// YSE has a very flexible vector class built in
	YSE::Pos pos;
	pos.zero();   YSE::Listener().pos(pos);
	
	sound1.pos(YSE::Pos(-3,0,3));
	sound2.pos(YSE::Pos(3,0,3));
}

This piece resets the demo:

  • Listener().pos(pos) puts the ear at the origin.

  • sound1.pos(YSE::Pos(-3, 0, 3)) places the drone three units left and three units in front of the listener.

  • sound2.pos(YSE::Pos(3, 0, 3)) places the kick three units right.

Reading a position#

The same method (overloaded) reads or writes. With no arguments it returns the current position:

void Demo3D::moveObject(direction d) {
	if (selectedObject < 3) {
		YSE::sound * s;
		if (selectedObject == 1) s = &sound1;
		else s = &sound2;
		YSE::Pos pos = s->pos();
		switch (d) {
		case FORWARD: pos.z += 0.5f; s->pos(pos); break;
		case BACKWARD: pos.z -= 0.5f; s->pos(pos); break;
		case LEFT: pos.x -= 0.5f; s->pos(pos); break;
		case RIGHT: pos.x += 0.5f; s->pos(pos); break;
		}
	}
	else {
		// you do not have to create the listener object, it's already there
		YSE::Pos pos = YSE::Listener().pos();
		switch (d) {
		case FORWARD: pos.z += 0.5f; YSE::Listener().pos(pos); break;
		case BACKWARD: pos.z -= 0.5f; YSE::Listener().pos(pos); break;
		case LEFT: pos.x -= 0.5f; YSE::Listener().pos(pos); break;
		case RIGHT: pos.x += 0.5f; YSE::Listener().pos(pos); break;
		}
	}
}

The pattern — fetch pos, modify it, write it back — is the idiomatic way to nudge an object’s position by a delta. The Listener works the same way: Listener().pos() reads, Listener().pos(p) writes.

Moving every frame#

In a real application, you would call Listener().pos(...) once per frame with the camera’s current position. The engine derives velocity from successive positions; the doppler effect kicks in automatically as long as updates are frequent (typically alongside YSE::System().update()).

If you also need orientation — for example to know which way the camera is facing — call Listener().orient(forward, up). The default up vector is (0, 1, 0), which constrains rotation to the horizontal plane.

What you learned#

  • YSE::Pos is the universal 3D coordinate. x / y / z are public floats; build with Pos(x, y, z) or zero().

  • sound.pos(p) writes, sound.pos() reads.

  • The YSE::Listener() singleton works the same way.

  • Doppler is automatic — keep updates frequent.

Next#