/* * Subdivides or unsubdivides this quad based on the current * viewer distance to this quad, relatively to its size. This * method uses the current viewer position provided by the * TerrainNode to which this quadtree belongs. */ public void Update() { Frustum.VISIBILTY v = (m_parent == null) ? Frustum.VISIBILTY.PARTIALLY : m_parent.GetVisible(); if (v == Frustum.VISIBILTY.PARTIALLY) { m_visible = m_owner.GetVisibility(m_localBox); } else { m_visible = v; } // here we reuse the occlusion test from the previous frame: // if the quad was found unoccluded in the previous frame, we suppose it is // still unoccluded at this frame. If it was found occluded, we perform // an occlusion test to check if it is still occluded. if (m_visible != Frustum.VISIBILTY.INVISIBLE && m_occluded) { m_occluded = m_owner.IsOccluded(m_localBox); if (m_occluded) { m_visible = Frustum.VISIBILTY.INVISIBLE; } } double ground = m_owner.GetView().GetGroundHeight(); double dist = m_owner.GetCameraDist(new Box3d(m_ox, m_ox + m_length, m_oy, m_oy + m_length, Math.Min(0.0, ground), Math.Max(0.0, ground))); if ((m_owner.GetSplitInvisibleQuads() || m_visible != Frustum.VISIBILTY.INVISIBLE) && dist < m_length * m_owner.GetSplitDist() && m_level < m_owner.GetMaxLevel()) { if (IsLeaf()) { Subdivide(); } int[] order = new int[4]; double ox = m_owner.GetLocalCameraPos().x; double oy = m_owner.GetLocalCameraPos().y; double cx = m_ox + m_length / 2.0; double cy = m_oy + m_length / 2.0; if (oy < cy) { if (ox < cx) { order[0] = 0; order[1] = 1; order[2] = 2; order[3] = 3; } else { order[0] = 1; order[1] = 0; order[2] = 3; order[3] = 2; } } else { if (ox < cx) { order[0] = 2; order[1] = 0; order[2] = 3; order[3] = 1; } else { order[0] = 3; order[1] = 1; order[2] = 2; order[3] = 0; } } m_children[order[0]].Update(); m_children[order[1]].Update(); m_children[order[2]].Update(); m_children[order[3]].Update(); // we compute a more precise occlusion for the next frame (see above), // by combining the occlusion status of the child nodes m_occluded = (m_children[0].GetOccluded() && m_children[1].GetOccluded() && m_children[2].GetOccluded() && m_children[3].GetOccluded()); } else { if (m_visible != Frustum.VISIBILTY.INVISIBLE) { // we add the bounding box of this quad to the occluders list m_occluded = m_owner.AddOccluder(m_localBox); if (m_occluded) { m_visible = Frustum.VISIBILTY.INVISIBLE; } } if (!IsLeaf()) { Release(); } } }