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VRDisplay: requestPresent() method

files/en-us/web/api/vrdisplay/requestpresent/index.md

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{{APIRef("WebVR API")}}{{Deprecated_Header}}{{Non-standard_Header}}

The requestPresent() method of the {{domxref("VRDisplay")}} interface starts the VRDisplay presenting a scene.

[!NOTE] This method was part of the old WebVR API. It has been superseded by the WebXR Device API.

Syntax

js-nolint
requestPresent(layers)

Parameters

  • layers
    • : An array of {{domxref("VRLayerInit")}} objects representing the scene you want to present. At the moment, this can be a minimum of 0 and a maximum of 1.

Return value

A promise that resolves once the presentation has begun. There are a number of rules surrounding the promise's fulfillment or rejection:

  • If {{domxref("VRDisplayCapabilities.canPresent")}} is false, or if the VRLayer array contains more than {{domxref("VRDisplayCapabilities.maxLayers")}} layers, the promise will be rejected.
  • If the {{domxref("VRDisplay")}} is already presenting when requestPresent() is called, the VRDisplay will update the VRLayer array being presented.
  • If a call to requestPresent() is rejected while the VRDisplay is already presenting it will end its presentation.
  • If requestPresent() is called outside of an engagement gesture the promise will be rejected unless the VRDisplay was already presenting. This engagement gesture is also sufficient to allow requestPointerLock() calls until presentation has ended.

Examples

js
if (navigator.getVRDisplays) {
  console.log("WebVR 1.1 supported");
  // Then get the displays attached to the computer
  navigator.getVRDisplays().then((displays) => {
    // If a display is available, use it to present the scene
    if (displays.length > 0) {
      vrDisplay = displays[0];
      console.log("Display found");
      // Starting the presentation when the button is clicked: It can only be called in response to a user gesture
      btn.addEventListener("click", () => {
        if (btn.textContent === "Start VR display") {
          vrDisplay.requestPresent([{ source: canvas }]).then(() => {
            console.log("Presenting to WebVR display");

            // Set the canvas size to the size of the vrDisplay viewport

            const leftEye = vrDisplay.getEyeParameters("left");
            const rightEye = vrDisplay.getEyeParameters("right");

            canvas.width =
              Math.max(leftEye.renderWidth, rightEye.renderWidth) * 2;
            canvas.height = Math.max(
              leftEye.renderHeight,
              rightEye.renderHeight,
            );

            // stop the normal presentation, and start the vr presentation
            window.cancelAnimationFrame(normalSceneFrame);
            drawVRScene();

            btn.textContent = "Exit VR display";
          });
        } else {
          vrDisplay.exitPresent();
          console.log("Stopped presenting to WebVR display");

          btn.textContent = "Start VR display";

          // Stop the VR presentation, and start the normal presentation
          vrDisplay.cancelAnimationFrame(vrSceneFrame);
          drawScene();
        }
      });
    }
  });
}

[!NOTE] You can see this complete code at raw-webgl-example.

Specifications

This method was part of the old WebVR API that has been superseded by the WebXR Device API. It is no longer on track to becoming a standard.

Until all browsers have implemented the new WebXR APIs, it is recommended to rely on frameworks, like A-Frame, Babylon.js, or Three.js, or a polyfill, to develop WebXR applications that will work across all browsers. Read Meta's Porting from WebVR to WebXR guide for more information.

Browser compatibility

{{Compat}}

See also