Quartz Quick Start

Quartz is a Blueprint-exposed scheduling system that solves timing issues between the game, audio logic, and audio rendering threads to provide sample-accurate audio playback.

This guide teaches you how to create a Quartz-powered metronome that triggers audio and gameplay events.

Prerequisites

Create a new Third Person Template project.

1 - Create the MetaSounds

Create two MetaSound Sources for the metronome beeps. Follow the steps below to build the graph above.

1.1 - Create the High-Frequency Beep

1. Create a MetaSound Source.

   1. In the Content Browser, click the Add button.

   2. Select Audio > MetaSound Source.

   3. Name the new MetaSound MSS_BeepA4.

2. Double-click the MetaSound to open the MetaSound Editor.

3. Find the On Play Input node and drag off of the pin into an empty space. Enter "AD Envelope (Audio)" into the node search to create a connected node. You can move the node around the graph by dragging it.

4. On the AD Envelope (Audio) node:

   1. Set Decay Time to 0.1.

   2. Connect the On Done pin to the On Finished Output node.

   3. Drag off the Out Envelope pin and create a Multiply (Audio) node.

5. On the Multiply (Audio) node:

   1. Drag off the bottom multiplicand pin and create a Sine node.

   2. Connect the output pin to the Out Mono Output node.

6. Click the Play button on the MetaSound Editor Toolbar to play the short, high-frequency beep sound.

7. Save the MetaSound and close the MetaSound Editor.

1.2 - Create the Low-Frequency Beep

1. In the Content Browser, right-click the MSS_BeepA4 MetaSound and select Duplicate.

2. Name the new MetaSound MSS_BeepA3.

3. Double-click the MetaSound to open the MetaSound Editor.

4. On the Sine node, set the Frequency to 220.

5. Click the Play button on the MetaSound Editor Toolbar to play the short, low-frequency beep sound.

6. Save the MetaSound and close the MetaSound Editor.

2 - Build the Level Blueprint

Construct the Level Blueprint to create a Quartz Clock, sounds, and the event delegate for the metronome.

2.1 - Create the Quartz Clock

1. On the Level Editor Toolbar, click the Blueprint button and select Open Level Blueprint.

2. Right-click in an empty space and add a Get QuartzSubsystem node.

3. On the Get QuartzSubsystem node, drag off the output pin and add a Create New Clock node.

4. On the Create New Clock node:

   1. Connect the Exec Input (>) pin to the Event BeginPlay node.

   2. Set Clock Name to LevelClock.

   3. Drag off the In Settings pin and add a Make QuartzClockSettings pin.

   4. Drag off the Return Value pin and select Promote to Variable. This creates a Set node and a Blueprint variable named NewVar to store the Quartz Clock Handle and prevent its' garbage collection.

   5. Connect the Exec Output (>) pin to the Set (NewVar) node.

5. In the My Blueprint panel, right-click the NewVar variable and select Rename.

6. Name the variable ClockHandle.

7. On the Make QuartzClockSettings node, drag off Time Signature and create a Make QuartzTimeSignature node.

8. On the Set (Clock Handle) node:

   1. Drag off the output pin and create a Set Beats Per Minute node.

   2. Connect the Exec Output (>) pin to the Set Beats Per Minute node.

9. On the Set Beats Per Minute node, set Beats Per Minute to 100.0.

2.2 - Create the Sounds

1. On the Set Beats Per Minute node (at the end of the previous section), drag off the Exec Output (>) pin and create a Create Sound 2D node.

2. On the Create Sound 2D node:

   1. Set Sound to MSS_BeepA4.

   2. Drag off the Return Value pin and select Promote to Variable. This creates a Set node and another Blueprint variable named NewVar.

   3. Drag off the Audio Component Output pin and create a Set Play Multiple Instances node.

   4. Connect the Exec Output (>) pin to the Set Play Multiple Instances node.

3. In the My Blueprint panel, right-click the NewVar variable and select Rename.

4. Name the variable BeepA4.

5. On the Set Play Multiple Instances node:

   1. Enable Play Multiple Instances.

   2. Drag off the Exec Output (>) pin and create a second Create Sound 2D node.

6. On the second Create Sound 2D node:

   1. Set Sound to MSS_BeepA3.

   2. Drag off the Return Value pin and select Promote to Variable. This creates a Set node and another Blueprint variable named NewVar.

   3. Drag off the Audio Component Output pin and create a second Set Play Multiple Instances node.

   4. Connect the Exec Output (>) pin to the Set Play Multiple Instances node.

7. In the My Blueprint panel, right-click the NewVar variable and select Rename.

8. Name the variable BeepA3.

9. On the second Set Play Multiple Instances node:

   1. Enable Play Multiple Instances.

2.3 - Start the Quartz Clock

1. Right-click in an empty space and add a Get Clock Handle node.

2. On the Get Clock Handle node, drag off the output pin and create a Start Clock node.

3. On the Start Clock node:

   1. Connect the Exec Input (>) pin to the second Set Play Multiple Instances node (at the end of the previous section).

   2. Drag off the Clock Handle node and create a Subscribe to All Quantization Events node.

   3. Connect the Exec Output (>) pin to the Subscribe to All Quantization Events node.

4. On the Subscribe to All Quantization Events node, drag off the On Quantization Event pin and create a Create Event node.

5. On the Create Event node:

   1. Click the dropdown and select [Create a matching event]. This creates a new Custom Event node.

   2. Name the Custom Event OnQuantizationEvent.

2.4 - Construct the Event Delegate

1. On the OnQuantizationEvent node:

   1. Drag off the QuantizationType pin and create a Switch on EQuartzCommandQuantization node.

   2. Connect the Exec Output (>) pin to the Switch on EQuartzCommandQuantization node.

   3. Drag off the QuantizationType pin and create a Make QuartzQuantizationBoundary node.

   4. Drag off the QuantizationType pin and create a second Make QuartzQuantizationBoundary node.

2. On both of the Make QuartzQuantizationBoundary nodes, set the Counting Reference Point to Transport Relative.

3. On the Switch on EQuartzCommandQuantization node:

   1. Drag off the Bar pin and create a Play Quantized node.

   2. Drag off the Beat pin and create a second Play Quantized node.

4. On the first Play Quantized node:

   1. Drag off the Target pin and create a Get Beep A4 node.

   2. Drag off the In Clock Handle pin and create a Get Clock Handle node.

   3. Connect the In Quantization Boundary pin to the output pin of one of the Make QuartzQuantizationBoundary nodes.

5. On the second Play Quantized node:

   1. Drag off the Target pin and create a Get Beep A3 node.

   2. Drag off the In Clock Handle pin and create a Get Clock Handle node.

   3. Connect the In Quantization Boundary pin to the output pin of the unconnected Make QuartzQuantizationBoundary node.

6. Compile and save the Blueprint.

7. Close the Blueprint Editor.

2.5 - Test the Level

Click the Play button on the Level Editor Toolbar. The low-frequency beep MetaSound plays every beat, and the high-frequency beep MetaSound plays every bar.

3 - Build the Blueprint Actor

Create a Blueprint Actor with a Cube Component that scales with the beat of the Quartz Clock that you set up on the Level Blueprint.

3.1 - Create the Blueprint Actor

1. In the Content Browser, click the Add button.

2. Select Blueprint Class.

3. From the Pick Parent Class window, select Actor.

4. Name the new Blueprint Actor BP_QuartzCube.

5. Double-click the Blueprint Actor to open the Blueprint Editor.

6. In the Components panel, click the Add button, type "Cube" into the search bar, and press Enter.

3.2 - Get the Level Clock on the Actor's Event Graph

1. Right-click in an empty space and add a Get QuartzSubsystem node.

2. On the Get QuartzSubsystem node, drag off the output pin and add a Get Handle for Clock node.

3. On the Get Handle for Clock node:

   1. Connect the Exec Input (>) pin to the Event BeginPlay node.

   2. Set Clock Name to LevelClock.

   3. Drag off the Return Value pin and create a Subscribe to Quantization Event node.

   4. Connect the Exec Output (>) pin to the Subscribe to Quantization Event node.

4. On the Subscribe to Quantization Event node:

   1. Set In Quantization Event to Beat.

   2. Drag off the Return Value pin and select Promote to Variable. This creates a Blueprint variable named Clock Handle to store the Quartz Clock Handle and prevent its' garbage collection.

   3. Connect the Exec Output (>) pin to the Set (Clock Handle) node.

   4. Drag off the On Quantization Event pin and create a Create Event node.

5. On the Create Event node:

   1. Click the dropdown and select [Create a matching event]. This will create a new Custom Event node.

   2. Name the Custom Event OnBeat.

3.3 - Scale the Actor on Beat

1. On the OnBeat node:

   1. Drag off the Exec Output (>) pin and create a Set Actor Scale 3D node.

   2. Connect the Beat pin to the New Scale 3D pin on the Set Actor Scale 3D node. This automatically creates a To Vector (Integer) node.

2. Compile and save the Blueprint.

3. Close the Blueprint Editor.

4 - Modify the Level Blueprint

Add logic to the Level Blueprint to spawn the BP_QuartzCube.

1. On the Level Editor Toolbar, click the Blueprint button and select Open Level Blueprint.

2. On the Subscribe to All Quantization Events node (in section 2.3), drag off the Exec Output (>) pin and create a Spawn Actor from Class node.

3. On the Spawn Actor node:

   1. Set Class to BP_QuartzCube.

   2. Drag off the Spawn Transform pin and select Promote to Variable.

4. Compile the Blueprint.

5. Select the Spawn Transform node.

6. In the Details panel, set the Default Value > Spawn Transform > Location to 1600.0, 1200.0, 200.0.

7. Compile and save the Blueprint.

8. Close the Blueprint Editor.

5 - Test the Level

Click the Play button on the Level Editor Toolbar. The BP_QuartzCube now spawns in the level and scales with the metronome beat.