HowTo's > Multithreading > Parallel Usage of Multiple Cameras

This topic explains how to use two cameras independently by running commands in separate execution nodes.

Please read the topics Opening a Camera and Grabbing 3D Data first.

Note: Rendering commands like RenderPointMap and RenderView use a single OpenGL context and therefore will be internally serialized and run sequentially, also when executed from separate Execute nodes. As these commands also have a single, global output node it is recommended to run at most one instance of each at a time.

Code Examples

Multi Threaded

Note: The code of the two threads only differs in the first two lines which specify a different execution node "thread1" or "thread2" and different camera serial number "1234" or "2345" to operate on.

Thread 1 (opens and uses camera "1234"):

std::string executionSlot = "thread1"; // Use a separate execution slot name for all commands carried out by this thread
std::string cameraSerial = "1234"; //replace "1234" with your camera's serial number

// Call the Open command to open the cameras
NxLibCommand open(cmdOpen, executionSlot); // Make sure to execute all commands in the execution slot for this thread, so they don't collide with thread 2
open.parameters()[itmCameras] = cameraSerial;
open.execute();

for (int imageIndex = 0; imageIndex < 10; imageIndex++) {
   // Execute the Capture and ComputeDisparityMap command only on our own camera
   NxLibCommand capture(cmdCapture, executionSlot);
   capture.parameters()[itmCameras] = cameraSerial;
   capture.execute();
   NxLibCommand computeDisparityMap(cmdComputeDisparityMap, executionSlot);
   computeDisparityMap.parameters()[itmCameras] = cameraSerial;
   computeDisparityMap.execute();
}

Thread 2 (opens and uses camera "2345"):

std::string executionSlot = "thread2"; // Use a separate execution slot name for all commands carried out by this thread
std::string cameraSerial = "2345"; //replace "2345" with your camera's serial number

// Call the Open command to open the cameras
NxLibCommand open(cmdOpen, executionSlot); // Make sure to execute all commands in the execution slot for this thread, so they don't collide with thread 1
open.parameters()[itmCameras] = cameraSerial;
open.execute();

for (int imageIndex = 0; imageIndex < 10; imageIndex++) {
   // Execute the Capture and ComputeDisparityMap command only on our own camera
   NxLibCommand capture(cmdCapture, executionSlot);
   capture.parameters()[itmCameras] = cameraSerial;
   capture.execute();
   NxLibCommand computeDisparityMap(cmdComputeDisparityMap, executionSlot);
   computeDisparityMap.parameters()[itmCameras] = cameraSerial;
   computeDisparityMap.execute();
}