C Specification

Foveated textures may have different sizes and aspect ratio compared to non-foveated textures. In order to determine recommended foveated texture size, an application can chain XrFoveatedViewConfigurationViewVARJO to XrViewConfigurationView and set foveatedRenderingActive to XR_TRUE. Since an application using foveated rendering with this extension has to render 4 views, https://www.khronos.org/registry/OpenXR/specs/1.0/html/xrspec.html#XR_VARJO_quad_views must be enabled along with this extension when XrInstance is created.

First and second views are non foveated views (covering whole field of view of HMD), third (left eye) and fourth (right eye) are foveated e.g. following gaze.

typedef struct XrFoveatedViewConfigurationViewVARJO {
    XrStructureType    type;
    void*              next;
    XrBool32           foveatedRenderingActive;
} XrFoveatedViewConfigurationViewVARJO;

Members

Member Descriptions
  • type is the XrStructureType of this structure.

  • next is NULL or a pointer to the next structure in a structure chain. No such structures are defined in core OpenXR or this extension.

  • foveatedRenderingActive is an XrBool32, indicating if the runtime should return foveated view configuration view.

Description

Valid Usage (Implicit)

For example:

XrInstance instance; // previously populated
XrSystemId systemId; // previously populated
XrViewConfigurationType viewConfigType; // Select XR_VIEW_CONFIGURATION_TYPE_PRIMARY_QUAD_VARJO

XrSystemFoveatedRenderingPropertiesVARJO foveatedRenderingProperties{XR_TYPE_SYSTEM_FOVEATED_RENDERING_PROPERTIES_VARJO};
XrSystemProperties systemProperties{XR_TYPE_SYSTEM_PROPERTIES, &foveatedRenderingProperties};
CHK_XR(xrGetSystemProperties(instance, systemId, &systemProperties));

uint32_t viewCount;
CHK_XR(xrEnumerateViewConfigurationViews(instance, systemId, viewConfigType, 0, &viewCount, nullptr));
// Non-foveated rendering views dimensions
std::vector<XrViewConfigurationView> configViews(viewCount, {XR_TYPE_VIEW_CONFIGURATION_VIEW});
CHK_XR(xrEnumerateViewConfigurationViews(instance, systemId, viewConfigType, viewCount, &viewCount, configViews.data()));

// Foveated rendering views dimensions
std::vector<XrViewConfigurationView> foveatedViews;
if (foveatedRenderingProperties.supportsFoveatedRendering && viewConfigType == XR_VIEW_CONFIGURATION_TYPE_PRIMARY_QUAD_VARJO) {
  std::vector<XrFoveatedViewConfigurationViewVARJO> requestFoveatedConfig{4, {XR_TYPE_FOVEATED_VIEW_CONFIGURATION_VIEW_VARJO, nullptr, XR_TRUE}};
  foveatedViews = std::vector<XrViewConfigurationView>{4, {XR_TYPE_VIEW_CONFIGURATION_VIEW}};
  for (size_t i = 0; i < 4; i++) {
    foveatedViews[i].next = &requestFoveatedConfig[i];
  }
  CHK_XR(xrEnumerateViewConfigurationViews(instance, systemId, viewConfigType, viewCount, &viewCount, foveatedViews.data()));
}
Example 1. Note

Applications using this extension are encouraged to create 2 sets of swapchains or one big enough set of swapchains and 2 sets of viewports. One set will be used when rendering gaze is not available and other one will be used when foveated rendering and rendering gaze is available. Using foveated textures may not provide optimal visual quality when rendering gaze is not available.

See Also

Document Notes

For more information, see the OpenXR Specification

This page is extracted from the OpenXR Specification. Fixes and changes should be made to the Specification, not directly.

Copyright (c) 2014-2021, The Khronos Group Inc.