Ogre中的射线查询一般只能侦测到边界盒（AABB）,就像你在下面图片看到的，使用下面的代码就能避免这些。
初始化射线查询：
|
1 2 3 4 5 6 7 8 |
// create the ray scene query object m_pray_scene_query = m_pscene_manager->createRayQuery(Ogre::Ray(), Ogre::SceneManager::WORLD_GEOMETRY_TYPE_MASK); if (NULL == m_pray_scene_query) { LOG_ERROR << "Failed to create Ogre::RaySceneQuery instance" << ENDLOG; return (false); } m_pray_scene_query->setSortByDistance(true); |
射线投射：
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 |
// raycast from a point in to the scene. // returns success or failure. // on success the point is returned in the result. bool OgreVisionEngine::RaycastFromPoint(const Vector3 &point, const Vector3 &normal, Vector3 &result) { // create the ray to test Ogre::Ray ray(Ogre::Vector3(point.x, point.y, point.z), Ogre::Vector3(normal.x, normal.y, normal.z)); // check we are initialised if (m_pray_scene_query != NULL) { // create a query object m_pray_scene_query->setRay(ray); // execute the query, returns a vector of hits if (m_pray_scene_query->execute().size() <= 0) { // raycast did not hit an objects bounding box return (false); } } else { LOG_ERROR << "Cannot raycast without RaySceneQuery instance" << ENDLOG; return (false); } // at this point we have raycast to a series of different objects bounding boxes. // we need to test these different objects to see which is the first polygon hit. // there are some minor optimizations (distance based) that mean we wont have to // check all of the objects most of the time, but the worst case scenario is that // we need to test every triangle of every object. Ogre::Real closest_distance = -1.0f; Ogre::Vector3 closest_result; Ogre::RaySceneQueryResult &query_result = m_pray_scene_query->getLastResults(); for (size_t qr_idx = 0; qr_idx < query_result.size(); qr_idx++) { // stop checking if we have found a raycast hit that is closer // than all remaining entities if ((closest_distance >= 0.0f) && (closest_distance < query_result[qr_idx].distance)) { break; } // only check this result if its a hit against an entity if ((query_result[qr_idx].movable != NULL) && (query_result[qr_idx].movable->getMovableType().compare("Entity") == 0)) { // get the entity to check Ogre::Entity *pentity = static_cast<Ogre::Entity*>(query_result[qr_idx].movable); // mesh data to retrieve size_t vertex_count; size_t index_count; Ogre::Vector3 *vertices; unsigned long *indices; // get the mesh information OgreVE::GetMeshInformation(pentity->getMesh(), vertex_count, vertices, index_count, indices, pentity->getParentNode()->getWorldPosition(), pentity->getParentNode()->getWorldOrientation(), pentity->getParentNode()->_getDerivedScale()); // test for hitting individual triangles on the mesh bool new_closest_found = false; for (int i = 0; i < static_cast<int>(index_count); i += 3) { // check for a hit against this triangle std::pair<bool, Ogre::Real> hit = Ogre::Math::intersects(ray, vertices[indices[i]], vertices[indices[i+1]], vertices[indices[i+2]], true, false); // if it was a hit check if its the closest if (hit.first) { if ((closest_distance < 0.0f) || (hit.second < closest_distance)) { // this is the closest so far, save it off closest_distance = hit.second; new_closest_found = true; } } } // free the verticies and indicies memory delete[] vertices; delete[] indices; // if we found a new closest raycast for this object, update the // closest_result before moving on to the next object. if (new_closest_found) { closest_result = ray.getPoint(closest_distance); } } } // return the result if (closest_distance >= 0.0f) { // raycast success result = closest_result; return (true); } else { // raycast failed return (false); } } |
得到网格信息：
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 |
// Get the mesh information for the given mesh. // Code found in Wiki: www.ogre3d.org/wiki/index.php/RetrieveVertexData void OgreVE::GetMeshInformation(const Ogre::MeshPtr mesh, size_t &vertex_count, Ogre::Vector3* &vertices, size_t &index_count, unsigned long* &indices, const Ogre::Vector3 &position, const Ogre::Quaternion &orient, const Ogre::Vector3 &scale) { bool added_shared = false; size_t current_offset = 0; size_t shared_offset = 0; size_t next_offset = 0; size_t index_offset = 0; vertex_count = index_count = 0; // Calculate how many vertices and indices we're going to need for (unsigned short i = 0; i < mesh->getNumSubMeshes(); ++i) { Ogre::SubMesh* submesh = mesh->getSubMesh( i ); // We only need to add the shared vertices once if(submesh->useSharedVertices) { if( !added_shared ) { vertex_count += mesh->sharedVertexData->vertexCount; added_shared = true; } } else { vertex_count += submesh->vertexData->vertexCount; } // Add the indices index_count += submesh->indexData->indexCount; } // Allocate space for the vertices and indices vertices = new Ogre::Vector3[vertex_count]; indices = new unsigned long[index_count]; added_shared = false; // Run through the submeshes again, adding the data into the arrays for ( unsigned short i = 0; i < mesh->getNumSubMeshes(); ++i) { Ogre::SubMesh* submesh = mesh->getSubMesh(i); Ogre::VertexData* vertex_data = submesh->useSharedVertices ? mesh->sharedVertexData : submesh->vertexData; if((!submesh->useSharedVertices)||(submesh->useSharedVertices && !added_shared)) { if(submesh->useSharedVertices) { added_shared = true; shared_offset = current_offset; } const Ogre::VertexElement* posElem = vertex_data->vertexDeclaration->findElementBySemantic(Ogre::VES_POSITION); Ogre::HardwareVertexBufferSharedPtr vbuf = vertex_data->vertexBufferBinding->getBuffer(posElem->getSource()); unsigned char* vertex = static_cast<unsigned char*>(vbuf->lock(Ogre::HardwareBuffer::HBL_READ_ONLY)); // There is _no_ baseVertexPointerToElement() which takes an Ogre::Real or a double // as second argument. So make it float, to avoid trouble when Ogre::Real will // be comiled/typedefed as double: // Ogre::Real* pReal; float* pReal; for( size_t j = 0; j < vertex_data->vertexCount; ++j, vertex += vbuf->getVertexSize()) { posElem->baseVertexPointerToElement(vertex, &pReal); Ogre::Vector3 pt(pReal[0], pReal[1], pReal[2]); vertices[current_offset + j] = (orient * (pt * scale)) + position; } vbuf->unlock(); next_offset += vertex_data->vertexCount; } Ogre::IndexData* index_data = submesh->indexData; size_t numTris = index_data->indexCount / 3; Ogre::HardwareIndexBufferSharedPtr ibuf = index_data->indexBuffer; if( ibuf.isNull() ) continue; // need to check if index buffer is valid (which will be not if the mesh doesn't have triangles like a pointcloud) bool use32bitindexes = (ibuf->getType() == Ogre::HardwareIndexBuffer::IT_32BIT); unsigned long* pLong = static_cast<unsigned long*>(ibuf->lock(Ogre::HardwareBuffer::HBL_READ_ONLY)); unsigned short* pShort = reinterpret_cast<unsigned short*>(pLong); size_t offset = (submesh->useSharedVertices)? shared_offset : current_offset; size_t index_start = index_data->indexStart; size_t last_index = numTris*3 + index_start; if (use32bitindexes) for (size_t k = index_start; k < last_index; ++k) { indices[index_offset++] = pLong[k] + static_cast<unsigned long>( offset ); } else for (size_t k = index_start; k < last_index; ++k) { indices[ index_offset++ ] = static_cast<unsigned long>( pShort[k] ) + static_cast<unsigned long>( offset ); } ibuf->unlock(); current_offset = next_offset; } } |
如果要考虑对处于运动状态物体做碰撞检测，可使用如下的得到网格信息代码（如果运动物体使用硬件蒙皮下面代码会出问题）：
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 |
void GetMeshInformation(const Entity *entity, size_t &vertex_count, Ogre::Vector3* &vertices, size_t &index_count, unsigned long* &indices, const Ogre::Vector3 &position, const Ogre::Quaternion &orient, const Ogre::Vector3 &scale) { bool added_shared = false; size_t current_offset = 0; size_t shared_offset = 0; size_t next_offset = 0; size_t index_offset = 0; vertex_count = index_count = 0; Ogre::MeshPtr mesh = entity->getMesh(); bool useSoftwareBlendingVertices = entity->hasSkeleton(); if (useSoftwareBlendingVertices) { entity->_updateAnimation(); } // Calculate how many vertices and indices we're going to need for (unsigned short i = 0; i < mesh->getNumSubMeshes(); ++i) { Ogre::SubMesh* submesh = mesh->getSubMesh( i ); // We only need to add the shared vertices once if(submesh->useSharedVertices) { if( !added_shared ) { vertex_count += mesh->sharedVertexData->vertexCount; added_shared = true; } } else { vertex_count += submesh->vertexData->vertexCount; } // Add the indices index_count += submesh->indexData->indexCount; } // Allocate space for the vertices and indices vertices = new Ogre::Vector3[vertex_count]; indices = new unsigned long[index_count]; added_shared = false; // Run through the submeshes again, adding the data into the arrays for ( unsigned short i = 0; i < mesh->getNumSubMeshes(); ++i) { Ogre::SubMesh* submesh = mesh->getSubMesh(i); //---------------------------------------------------------------- // GET VERTEXDATA //---------------------------------------------------------------- //Ogre::VertexData* vertex_data = submesh->useSharedVertices ? mesh->sharedVertexData : submesh->vertexData; Ogre::VertexData* vertex_data; //When there is animation: if(useSoftwareBlendingVertices) vertex_data = submesh->useSharedVertices ? entity->_getSkelAnimVertexData() : entity->getSubEntity(i)->_getSkelAnimVertexData(); else vertex_data = submesh->useSharedVertices ? mesh->sharedVertexData : submesh->vertexData; if((!submesh->useSharedVertices)||(submesh->useSharedVertices && !added_shared)) { if(submesh->useSharedVertices) { added_shared = true; shared_offset = current_offset; } const Ogre::VertexElement* posElem = vertex_data->vertexDeclaration->findElementBySemantic(Ogre::VES_POSITION); Ogre::HardwareVertexBufferSharedPtr vbuf = vertex_data->vertexBufferBinding->getBuffer(posElem->getSource()); unsigned char* vertex = static_cast<unsigned char*>(vbuf->lock(Ogre::HardwareBuffer::HBL_READ_ONLY)); // There is _no_ baseVertexPointerToElement() which takes an Ogre::Real or a double // as second argument. So make it float, to avoid trouble when Ogre::Real will // be comiled/typedefed as double: // Ogre::Real* pReal; float* pReal; for( size_t j = 0; j < vertex_data->vertexCount; ++j, vertex += vbuf->getVertexSize()) { posElem->baseVertexPointerToElement(vertex, &pReal); Ogre::Vector3 pt(pReal[0], pReal[1], pReal[2]); vertices[current_offset + j] = (orient * (pt * scale)) + position; } vbuf->unlock(); next_offset += vertex_data->vertexCount; } Ogre::IndexData* index_data = submesh->indexData; size_t numTris = index_data->indexCount / 3; Ogre::HardwareIndexBufferSharedPtr ibuf = index_data->indexBuffer; bool use32bitindexes = (ibuf->getType() == Ogre::HardwareIndexBuffer::IT_32BIT); unsigned long* pLong = static_cast<unsigned long*>(ibuf->lock(Ogre::HardwareBuffer::HBL_READ_ONLY)); unsigned short* pShort = reinterpret_cast<unsigned short*>(pLong); size_t offset = (submesh->useSharedVertices)? shared_offset : current_offset; size_t index_start = index_data->indexStart; size_t last_index = numTris*3 + index_start; if (use32bitindexes) for (size_t k = index_start; k < last_index; ++k) { indices[index_offset++] = pLong[k] + static_cast<unsigned long>( offset ); } else for (size_t k = index_start; k < last_index; ++k) { indices[ index_offset++ ] = static_cast<unsigned long>( pShort[k] ) + static_cast<unsigned long>( offset ); } ibuf->unlock(); current_offset = next_offset; } } |
总的原理是进行射线查询，然后获取模型mesh顶点与索引信息，将每三个顶点构成一个三角面，将定义好的射线与这些三角面进行相交，得到距离最近的交点，射线发射点与该交点距离即为最近距离，最后返回该最近距离。
具体代码使用大家可以参考MOC这个轻量级的碰撞检测库，官网上有示例，可以很容易的掌握。
文章评论