a 3D ship in a 3D realm...
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This is taken from donuts3D on the directx8 SDK, but probably applies to other games too.
What does the Point of ship, Point ahead of ship, and Point to side of ship mean? does it mean the vectors in the Centre/center of the model, the front of the model (the nose), and the furthest right sided point of the model?
// Render the ship
if( g_pShip->bVisible && g_bFirstPersonView == FALSE )
{
// Point of ship, on terrain
D3DXVECTOR3 vShipPt; // vector declaration
vShipPt.x = g_pShip->vPos.x; // x position
vShipPt.z = -g_pShip->vPos.y; // z position
vShipPt.y = 0.1f + HeightField( vShipPt.x, vShipPt.z ); // y position is computed
// Point ahead of ship, on terrain
D3DXVECTOR3 vForwardPt; // vector declaration
vForwardPt.x = vShipPt.x+sinf(g_pShip->fAngle);
vForwardPt.z = vShipPt.z+cosf(g_pShip->fAngle);
vForwardPt.y = 0.1f + HeightField( vForwardPt.x, vForwardPt.z );
// Point to side of ship, on terrain
D3DXVECTOR3 vSidePt;
vSidePt.x = vShipPt.x+sinf(g_pShip->fAngle + D3DX_PI/2.0f);
vSidePt.z = vShipPt.z+cosf(g_pShip->fAngle + D3DX_PI/2.0f);
vSidePt.y = 0.1f + HeightField( vSidePt.x, vSidePt.z );
Observe everything, remember more!
To fully specify the position and orientation of an object in 3D space, you need 2 vectors: one along the object''s direction and another perpendicular to that (many people use "front" and "up", but "front" and "right" [or left] work just as well)
So I said we need 2 vectors, but they declare 3 points. Why? Because a vector has 2 points - a begin point (origin) and an endpoint. The direction vector ("front") has origin at the ships position and its endpoint at the point in front of the ship, while the side vector ("left" or "right") extends from the position to the point by the ship''s side.
Alles klar?
So I said we need 2 vectors, but they declare 3 points. Why? Because a vector has 2 points - a begin point (origin) and an endpoint. The direction vector ("front") has origin at the ships position and its endpoint at the point in front of the ship, while the side vector ("left" or "right") extends from the position to the point by the ship''s side.
Alles klar?
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