float LaserPhysicsComponent::getAsteroidBoundingSphereRadius(Asteroid &asteroid)
{
D3DXVECTOR3 asteroidScale = asteroid.getScale();
float maxRadius = max<float>(ASTEROID_BASE_X * asteroidScale.x, ASTEROID_BASE_Y * asteroidScale.y);
maxRadius = max<float>(maxRadius, ASTEROID_BASE_Z * asteroidScale.z);
return maxRadius;
}
bool LaserPhysicsComponent::testIntersectionWithAsteroid(Laser &laser, Asteroid &asteroid)
{
D3DXVECTOR3 currLaserPos = laser.getPosition(), lastLaserPos = laser.getLastPosition(),
laserDir = laser.getDirection(), asteroidPosition = asteroid.getPosition();
float asteroidRadius = getAsteroidBoundingSphereRadius(asteroid);
float asteroidPosToLaserEnd;
//check if the laser ray intersects a rough bounding sphere of the asteroid
if (!D3DXSphereBoundProbe(&asteroidPosition, asteroidRadius, &lastLaserPos, &laserDir)) {
return false;
}
asteroidPosToLaserEnd = D3DXVec3LengthSq(&(currLaserPos - asteroidPosition));
//if this is true then the laser's current position does not fall within the sphere, and a ray starting at the laser's
//current point crosses the circle. A ray starting at the last point already crosses the sphere, so this means both
//points are "before" the sphere, along the ray in the direction the laser is travelling.
if (asteroidRadius * asteroidRadius < asteroidPosToLaserEnd &&
D3DXSphereBoundProbe(&asteroidPosition, asteroidRadius, &currLaserPos, &laserDir)) {
return false;
}
//it may have collided. Now check ray against mesh
shared_ptr<GraphicsComponent> gfx = asteroid.getGraphicsComponent();
AsteroidGraphicsComponent *asteroidGraphicsComponent = dynamic_cast<AsteroidGraphicsComponent*>(gfx.get());
if (asteroidGraphicsComponent == NULL) {
throw "Asteroid didn't have a valid asteroid graphics component!";
}
BOOL hit;
float dist;
D3DXVECTOR3 laserPosRelativeToAsteroid = lastLaserPos - asteroidPosition;
D3DXVECTOR3 asteroidScale = asteroid.getScale();
D3DXQUATERNION rotationQuat = asteroid.getRotationQuat();
D3DXMATRIX rot, scale;
D3DXMatrixScaling(&scale, 0.8f/asteroidScale.x, 0.8f/asteroidScale.y, 0.8f/asteroidScale.z);
D3DXMatrixRotationQuaternion(&rot, &rotationQuat);
D3DXVec3TransformCoord(&laserPosRelativeToAsteroid, &laserPosRelativeToAsteroid, &(scale * rot));
D3DXIntersect(asteroidGraphicsComponent->getMesh(),
&laserPosRelativeToAsteroid,
&laserDir,
&hit,
NULL,
NULL,
NULL,
&dist,
NULL,
NULL);
float distTravelledSq = D3DXVec3LengthSq(&(currLaserPos - lastLaserPos));
if (!hit || dist * dist > D3DXVec3LengthSq(&(currLaserPos - lastLaserPos))) {
return false;
}
return true;
}