unproject function
On success, Sets pickWorld
to be the world space position of
the screen space pickX
, pickY
, and pickZ
.
The viewport is specified by (viewportX
, viewportWidth
) and
(viewportY
, viewportHeight
).
cameraMatrix
includes both the projection and view transforms.
pickZ
is typically either 0.0 (near plane) or 1.0 (far plane).
Returns false on error, for example, the mouse is not in the viewport
Implementation
bool unproject(
Matrix4 cameraMatrix,
num viewportX,
num viewportWidth,
num viewportY,
num viewportHeight,
num pickX,
num pickY,
num pickZ,
Vector3 pickWorld) {
viewportX = viewportX.toDouble();
viewportWidth = viewportWidth.toDouble();
viewportY = viewportY.toDouble();
viewportHeight = viewportHeight.toDouble();
pickX = pickX.toDouble();
pickY = pickY.toDouble();
pickX = pickX - viewportX;
pickY = pickY - viewportY;
pickX = (2.0 * pickX / viewportWidth) - 1.0;
pickY = (2.0 * pickY / viewportHeight) - 1.0;
pickZ = (2.0 * pickZ) - 1.0;
// Check if pick point is inside unit cube
if (pickX < -1.0 ||
pickY < -1.0 ||
pickX > 1.0 ||
pickY > 1.0 ||
pickZ < -1.0 ||
pickZ > 1.0) {
return false;
}
// Copy camera matrix.
final invertedCameraMatrix = Matrix4.copy(cameraMatrix);
// Invert the camera matrix.
invertedCameraMatrix.invert();
// Determine intersection point.
final v = Vector4(pickX.toDouble(), pickY.toDouble(), pickZ.toDouble(), 1.0);
invertedCameraMatrix.transform(v);
if (v.w == 0.0) {
return false;
}
final invW = 1.0 / v.w;
pickWorld
..x = v.x * invW
..y = v.y * invW
..z = v.z * invW;
return true;
}