using an {{XRProjectionLayer}} |layer|, an {{XRTextureType}} |textureType|, a {{GLenum}} |textureFormat| and a float |scaleFactor|, the user agent MUST run the following steps:
- 1. Let |array| be a [=new=] array in the [=relevant realm=] of |context|.
1. Let |context| be |layer|'s [=XRCompositionLayer/context=].
+ 1. Let |array| be a [=new=] array in the [=relevant realm=] of |context|.
1. Let |session| be |layer|'s [=XRCompositionLayer/session=].
1. If |textureFormat| is
, return |array| and abort these steps.
1. If |context| is a {{WebGLRenderingContext}} and the {{WEBGL_depth_texture}} [=extension=] is not enabled in |context|, return |array| and abort these steps.
1. If |textureFormat| is not in the [=list of depth formats for projection layers=], throw a {{NotSupportedError}} and abort these steps.
1. let |numViews| be the number of the |session|'s [=list of views=] excluding the [=secondary view|secondary views=].
1. Let |view| be the first entry in the |session|'s [=list of views=] that is not a [=secondary view=].
- 1. Let |width| be the width of |view|'s [=recommended WebGL depth texture resolution=] multiplied by |scaleFactor|.
- 1. Let |height| be the height of |view|'s [=recommended WebGL depth texture resolution=] multiplied by |scaleFactor|.
+ 1. Let |recommendedDepthResolution| be |view|'s [=recommended WebGL depth texture resolution=].
+ 1. If |session| was created with the "[=space-warp=]" [=feature descriptor=], set |recommendedDepthResolution| to |view|'s [=recommended motion vector texture resolution=].
+ 1. Let |width| be the width of |recommendedDepthResolution| multiplied by |scaleFactor|.
+ 1. Let |height| be the height of |recommendedDepthResolution| multiplied by |scaleFactor|.
1. If |layer|'s {{XRCompositionLayer/layout}} is {{XRLayerLayout/"mono"}} or {{XRLayerLayout/"default"}}:
- 1. If the session’s [=view|views=] in the [=list of views=] don't all have the same [=recommended WebGL color texture resolution=] excluding the [=secondary view|secondary views=], throw a {{NotSupportedError}} and abort these steps.
+ 1. If |session| was created with the "[=space-warp=]" [=feature descriptor=] and the session’s [=view|views=] in the [=list of views=] don't all have the same [=recommended motion vector texture resolution=] excluding the [=secondary view|secondary views=], throw a {{NotSupportedError}} and abort these steps.
+ 1. If |session| was not created with the "[=space-warp=]" [=feature descriptor=] and the session’s [=view|views=] in the [=list of views=] don't all have the same [=recommended WebGL depth texture resolution=] excluding the [=secondary view|secondary views=], throw a {{NotSupportedError}} and abort these steps.
1. If |layer|'s {{XRCompositionLayer/layout}} is {{XRLayerLayout/stereo-left-right}}, initialize |array| with 1 [=new=] instance of an [=opaque texture=] in the [=relevant realm=] of |context| created as a |textureType| texture using |context|, |textureFormat|, |stencil|, |numViews| multiplied by |width| and |height|.
1. If |layer|'s {{XRCompositionLayer/layout}} is {{XRLayerLayout/stereo-top-bottom}}, initialize |array| with 1 [=new=] instance of an [=opaque texture=] in the [=relevant realm=] of |context| created as a |textureType| texture using |context|, |textureFormat|, |stencil|, |width| and |numViews| multiplied by |height|.
1. If the [=opaque texture=] was unable to be created for any reason, throw an {{OperationError}} and abort these steps.
@@ -1295,9 +1280,9 @@ To
-To
allocate motion vector textures for projection layers using an {{XRProjectionLayer}} |layer|, the user agent MUST run the following steps:
- 1. Let |array| be a [=new=] array in the [=relevant realm=] of |context|.
+To
allocate motion vector textures for projection layers using an {{XRProjectionLayer}} |layer|, an {{XRTextureType}} |textureType| and a float |scaleFactor|, the user agent MUST run the following steps:
1. Let |context| be |layer|'s [=XRCompositionLayer/context=].
+ 1. Let |array| be a [=new=] array in the [=relevant realm=] of |context|.
1. Let |session| be |layer|'s [=XRCompositionLayer/session=].
1. If |session| was not created with the "[=space-warp=]" [=feature descriptor=], return |array| and abort these steps.
1. If |context| is a {{WebGLRenderingContext}} and the {{WEBGL_depth_texture}} [=extension=] is not enabled in |context|, return |array| and abort these steps.
@@ -1455,6 +1440,8 @@ When this method is invoked, the user agent MUST run the following steps:
1. Initialize |layer|'s [=XRCompositionLayer/isStatic=] to
false.
1. Initialize |layer|'s {{XRProjectionLayer/ignoreDepthValues}} as follows:
+ - If |session| was created with the "[=space-warp=]" [=feature descriptor=]
+
- Initialize |layer|'s {{XRProjectionLayer/ignoreDepthValues}} to
false
- If |init|'s {{XRProjectionLayerInit/depthFormat}} is
false and the [=XR Compositor=] will make use of depth values
- Initialize |layer|'s {{XRProjectionLayer/ignoreDepthValues}} to
false
- Otherwise
@@ -1468,7 +1455,7 @@ When this method is invoked, the user agent MUST run the following steps:
1. Initialize |layer|'s {{XRCompositionLayer/needsRedraw}} to
true.
1. let |layer|'s [=colorTextures=] be the result of [=allocate color textures for projection layers|allocating color textures for projection layers=] with |layer|, |init|'s {{XRProjectionLayerInit/textureType}}, |init|'s {{XRProjectionLayerInit/colorFormat}} and |init|'s {{XRProjectionLayerInit/scaleFactor}}.
1. let |layer|'s [=depthStencilTextures=] be the result of [=allocate depth textures for projection layers|allocating depth textures for projection layers=] with |layer|, |init|'s {{XRProjectionLayerInit/textureType}}, |init|'s {{XRProjectionLayerInit/depthFormat}} and |init|'s {{XRProjectionLayerInit/scaleFactor}}.
- 1. let |layer|'s [=motionVectorTextures=] be the result of [=allocate motion vector textures for projection layers|allocating motion vector textures for projection layers=] with |layer|, |init|'s {{XRProjectionLayerInit/depthFormat}} and |init|'s {{XRProjectionLayerInit/scaleFactor}}.
+ 1. let |layer|'s [=motionVectorTextures=] be the result of [=allocate motion vector textures for projection layers|allocating motion vector textures for projection layers=] with |layer|, |init|'s {{XRProjectionLayerInit/textureType}} and |init|'s {{XRProjectionLayerInit/scaleFactor}}.
1. Initialize the [=XRProjectionLayer/colortextures for secondary views=] as follows:
- If the |session| was created with "[=secondary view/secondary-views=]" enabled
@@ -1727,7 +1714,7 @@ When this method is invoked on an {{XRWebGLBinding}} |binding|, it MUST run the
- Otherwise
- Initialize |subimage|'s {{XRWebGLSubImage/depthStencilTexture}} with the first element of |layer|'s [=depthStencilTextures=] array.
- 1. Initialize |subimage|'s {{XRWebGLSubImage/motionVectorTexture}}, {{XRWebGLSubImage/motionVectorTextureWidth}} and {{XRWebGLSubImage/motionVectorTextureHeight}} with null.
+ 1. Initialize |subimage|'s {{XRWebGLSubImage/depthStencilTextureWidth}}, {{XRWebGLSubImage/depthStencilTextureHeight}}, and {{XRWebGLSubImage/motionVectorTexture}} with null.
1. Set |subimage|'s {{XRWebGLSubImage/colorTextureWidth}} to the pixel width of |subimage|'s {{XRWebGLSubImage/colorTexture}}.
1. Set |subimage|'s {{XRWebGLSubImage/colorTextureHeight}} to the pixel height of |subimage|'s {{XRWebGLSubImage/colorTexture}}.
1. If |subimage|'s {{XRWebGLSubImage/depthStencilTexture}} is not null, set |subimage|'s {{XRWebGLSubImage/depthStencilTextureWidth}} to the pixel width of the first texture in the {{XRWebGLSubImage/depthStencilTexture}} array.
@@ -1803,10 +1790,9 @@ When this method is invoked on an {{XRWebGLBinding}} |binding|, it MUST run the
1. Set |subimage|'s {{XRWebGLSubImage/colorTextureWidth}} to the pixel width of |subimage|'s {{XRWebGLSubImage/colorTexture}}.
1. Set |subimage|'s {{XRWebGLSubImage/colorTextureHeight}} to the pixel height of |subimage|'s {{XRWebGLSubImage/colorTexture}}.
+ 1. Initialize |subimage|'s {{XRWebGLSubImage/depthStencilTextureWidth}} and {{XRWebGLSubImage/depthStencilTextureHeight}} with
null.
1. If |subimage|'s {{XRWebGLSubImage/depthStencilTexture}} is not
null, set |subimage|'s {{XRWebGLSubImage/depthStencilTextureWidth}} to the pixel width of the first texture in the {{XRWebGLSubImage/depthStencilTexture}} array.
1. If |subimage|'s {{XRWebGLSubImage/depthStencilTexture}} is not
null, set |subimage|'s {{XRWebGLSubImage/depthStencilTextureHeight}} to the pixel height of the first texture in the {{XRWebGLSubImage/depthStencilTexture}} array.
- 1. If |subimage|'s {{XRWebGLSubImage/motionVectorTexture}} is not
null, set |subimage|'s {{XRWebGLSubImage/motionVectorTextureWidth}} to the pixel width of the first texture in the {{XRWebGLSubImage/motionVectorTexture}} array.
- 1. If |subimage|'s {{XRWebGLSubImage/motionVectorTexture}} is not
null, set |subimage|'s {{XRWebGLSubImage/motionVectorTextureHeight}} to the pixel height of the first texture in the {{XRWebGLSubImage/motionVectorTexture}} array.
1. Run [=initialize the viewport=] on |subimage|'s {{XRSubImage/viewport}} with |subimage|'s {{XRWebGLSubImage/colorTexture}}, |layer|'s {{XRCompositionLayer/layout}}, |index| and the number of the |session|'s [=list of views=].
1. Set {{XRCompositionLayer/needsRedraw}} to
false.
1. return |subimage|
@@ -2097,18 +2083,22 @@ Other layers types MUST continue to be sorted as before.
Space warp {#spacewarp}
==========
-
Space warp is a technology that improves the [=XR Compositor=]'s reprojection.
By submitting a {{XRWebGLSubImage/motionVectorTexture}} along with a {{XRWebGLSubImage/depthStencilTexture}}
-the [=XR Compositor=] can do high quality frame extrapolation and reprojection which allows the user agent to run at a reduced framerate but still provide a smooth experience to users.
+the [=XR Compositor=] can do high quality frame extrapolation and reprojection which allows the user agent to run at a reduced framerate but still provide a smooth experience to users. The rate at which {{XRSession/requestAnimationFrame()}} callbacks are delivered may be lower than the display's native refresh rate. The [=XR Compositor=] will synthesize the missing frames using the motion vectors and depth information provided by the experience.
To enable [=space warp=] the {{XRSession}} MUST be created with the "space-warp" [=feature descriptor=].
If "[=space-warp=]" is enabled, the [=XR Compositor=] MUST make use of depth values, {{XRProjectionLayer/ignoreDepthValues}} MUST be set to `false` and {{XRWebGLBinding/usesDepthValues}} MUST be set to `true`.
-The {{XRWebGLSubImage/motionVectorTexture}} MUST be in {{RGBA16F}} format. The author SHOULD fill in the RGB components of this texture with the speed in meters per second of that area with the red pixel corresponding with the x axis, green the y axis and blue the z axis.
+When the [=feature descriptor/space-warp=] [=feature descriptor=] is enabled, the experience should render representative depth values into the {{XRWebGLSubImage/depthStencilTexture}} for each {{XRProjectionLayer}} it submits.
+The {{XRWebGLSubImage/depthStencilTexture}} and {{XRWebGLSubImage/motionVectorTexture}} will have the same dimensions, which may be different from the dimensions of the {{XRWebGLSubImage/colorTexture}}.
+Authors can use {{XRWebGLSubImage/depthStencilTextureWidth}} and {{XRWebGLSubImage/depthStencilTextureHeight}} to determine the dimensions of both the depth/stencil and motion vector attachments.
-
+NOTE: Since the depth/stencil attachment can have different dimensions than the color attachment, it is not intended to be attached to the framebuffer used to render into the {{XRWebGLSubImage/colorTexture}}.
+Authors should render depth/stencil information separately at the depth/stencil attachment dimensions.
+
+The {{XRWebGLSubImage/motionVectorTexture}} MUST be in {{RGBA16F}} format. The author SHOULD fill in the RG components of this texture with the 2D screen-space motion vector for that area, expressed as a delta in
Normalized Device Coordinates (
NDC) between the current frame and the previous frame. The motion vector is computed as `(currentClipPos / currentW) - (prevClipPos / prevW)`, where `currentClipPos` and `prevClipPos` are the
clip space positions of the fragment in the current and previous frames, respectively. The red channel corresponds to the delta in [=NDC=] X (horizontal), and the green channel corresponds to the delta in [=NDC=] Y (vertical). The blue channel MAY contain the delta in [=NDC=] Z (depth), and the alpha channel is unused.
WebXR Device API Integration {#webxrintegration}
============================
@@ -2184,8 +2174,9 @@ resolution large enough to contain the view.
If the {{XRSession}} was created with the "[=feature descriptor/space-warp=]" [=feature descriptor=], each [=view=] MUST define a
recommended motion vector texture resolution which is based on the [=recommended WebGL color texture resolution=].
-Each [=view=] MUST also define a
recommended WebGL depth texture resolution which is based on the [=recommended WebGL color texture resolution=] and [=recommended motion vector texture resolution=]. The user agent MAY decide to reduce the
-[=recommended WebGL depth texture resolution=] if "[=feature descriptor/space-warp=]" is enabled.
+Each [=view=] MUST also define a
recommended WebGL depth texture resolution which represents a best estimate of the WebGL depth texture
+resolution large enough to contain the view.
+If the {{XRSession}} was created with the "[=feature descriptor/space-warp=]" [=feature descriptor=], the [=recommended WebGL depth texture resolution=] MUST be equal to the [=recommended motion vector texture resolution=].