FAQ: How can I see the participant's gaze overlaid on the stimulus during data collection?

[SR-SUPPORT]

When recording gaze data, you can display a background on the Host PC screen to provide context for the participant's real-time gaze position. This can be done by transferring a static image, drawing a "primitive" (simplified) representation of the stimuli, or sending custom drawing commands.

   

1. Transfer a Static Image
   This method sends a single, static image from a select DISPLAY_SCREEN action in your task and transfers it to the Host PC background.
   
   In your trial sequence, make sure a PREPARE_SEQUENCE action node comes before your Recording Sequence and in that PREPARE_SEQUENCE node, set the Draw to EyeLink Host property to IMAGE.
   
      
   
   Within the main Recording Sequence, find the DISPLAY_SCREEN node that shows the image you want to transfer. Check its Use for Host Display property.
   
      
   
   Important: Only the last DISPLAY_SCREEN node with this property checked will be transferred. If a video is used, only its first frame will be sent to the Host PC.
   
   Note: While only one image appears on the Host PC during recording, all stimuli (images and videos) will be displayed correctly in Data Viewer's Spatial Overlay and Trial Animation Playback modes.
   
   
2. Draw Primitive Shapes
   This option draws basic shapes on the Host PC to represent the location of stimuli. For example, if the participant sees two images side-by-side, the Host PC will show two empty rectangles in the same positions. This is useful when a full-color image makes it difficult to see the gaze cursor.
   
   To use this mode, follow the same setup steps as above, but set the Draw to EyeLink Host property in the PREPARE_SEQUENCE node to PRIMITIVE.
   
   
3. Use Drawing Commands
   For experiments with complex or moving stimuli (like a smooth pursuit task), it may be better to represent areas of interest with simple, custom-drawn shapes. For instance, you could draw lines to indicate a target's path and squares to mark its start and end points.
   
   You can send drawing commands to the Host PC from an Experiment Builder script. The Pursuit project, included with the Experiment Builder Examples, provides a great template in its DRAW_FEEDBACK_GRAPHICS_TO_HOST sequence.
   
   A full list of drawing commands is documented in the COMMANDS.INI file, which you can find in the following locations on the Host PC's hard drive:
   • /EYELINK2/EXE/ (for EyeLink II)
     
   • /ELCL/EXE/ (for EyeLink 1000 and 1000 Plus)
     
   You can access this file using the File Manager on the Host PC or through a web browser on the Display PC by navigating to the Host PC IP address (e.g. http://100.1.1.1) while the Host PC is in File Manager mode.