Package org.lwjgl.vulkan

Class QCOMRenderPassTransform

java.lang.Object

org.lwjgl.vulkan.QCOMRenderPassTransform

public final class QCOMRenderPassTransform
extends Object

This extension provides a mechanism for applications to enable driver support for render pass transform.

Mobile devices can be rotated and mobile applications need to render properly when a device is held in a landscape or portrait orientation. When the current orientation differs from the device’s native orientation, a rotation is required so that the “up” direction of the rendered scene matches the current orientation.

If the Display Processing Unit (DPU) does not natively support rotation, the Vulkan presentation engine can handle this rotation in a separate composition pass. Alternatively, the application can render frames “pre-rotated” to avoid this extra pass. The latter is preferred to reduce power consumption and achieve the best performance because it avoids tasking the GPU with extra work to perform the copy/rotate operation.

Unlike OpenGL ES, the burden of pre-rotation in Vulkan falls on the application. To implement pre-rotation, applications render into swapchain images matching the device native aspect ratio of the display and “pre-rotate” the rendering content to match the device’s current orientation. The burden is more than adjusting the Model View Projection (MVP) matrix in the vertex shader to account for rotation and aspect ratio. The coordinate systems of scissors, viewports, derivatives and several shader built-ins may need to be adapted to produce the correct result.

It is difficult for some game engines to manage this burden; many chose to simply accept the performance/power overhead of performing rotation in the presentation engine.

This extension allows applications to achieve the performance benefits of pre-rotated rendering by moving much of the above-mentioned burden to the graphics driver. The following is unchanged with this extension:

• Applications create a swapchain matching the native orientation of the display. Applications must also set the VkSwapchainCreateInfoKHR::preTransform equal to the currentTransform as returned by GetPhysicalDeviceSurfaceCapabilitiesKHR.

The following is changed with this extension:

• At CmdBeginRenderPass, the application provides extension struct VkRenderPassTransformBeginInfoQCOM specifying the render pass transform parameters.
• At BeginCommandBuffer for secondary command buffers, the application provides extension struct VkCommandBufferInheritanceRenderPassTransformInfoQCOM specifying the render pass transform parameters.
• The renderArea, viewports, scissors, and fragmentSize are all provided in the current (non-rotated) coordinate system. The implementation will transform those into the native (rotated) coordinate system.
• The implementation is responsible for transforming shader built-ins (FragCoord, PointCoord, SamplePosition, PrimitiveShadingRateKHR, interpolateAt(), dFdx, dFdy, fWidth) into the rotated coordinate system.
• The implementation is responsible for transforming position to the rotated coordinate system.
• If this extension is used with VK_QCOM_tile_properties, then GetFramebufferTilePropertiesQCOM and GetDynamicRenderingTilePropertiesQCOM return tile properties in the rotated coordinate space.

Name String

VK_QCOM_render_pass_transform

Extension Type

Device extension

Registered Extension Number

283

Revision

4

Contact

• Matthew Netsch mnetsch

Other Extension Metadata

Last Modified Date

2023-12-13

Interactions and External Dependencies

• This extension interacts with VK_KHR_swapchain
• This extension interacts with VK_KHR_surface
• This extension interacts with VK_EXT_fragment_density_map
• This extension interacts with VK_KHR_fragment_shading_rate
• This extension interacts with VK_QCOM_tile_properties

Contributors

• Jeff Leger, Qualcomm Technologies, Inc.
• Brandon Light, Qualcomm Technologies, Inc.
• Matthew Netsch, Qualcomm Technologies, Inc.
• Arpit Agarwal, Qualcomm Technologies, Inc.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	VK_QCOM_RENDER_PASS_TRANSFORM_EXTENSION_NAME	The extension name.
static final int	VK_QCOM_RENDER_PASS_TRANSFORM_SPEC_VERSION	The extension specification version.
static final int	VK_RENDER_PASS_CREATE_TRANSFORM_BIT_QCOM	Extends VkRenderPassCreateFlagBits.
static final int	VK_STRUCTURE_TYPE_COMMAND_BUFFER_INHERITANCE_RENDER_PASS_TRANSFORM_INFO_QCOM	Extends VkStructureType.
static final int	VK_STRUCTURE_TYPE_RENDER_PASS_TRANSFORM_BEGIN_INFO_QCOM	Extends VkStructureType.

Method Summary

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

VK_QCOM_RENDER_PASS_TRANSFORM_SPEC_VERSION

public static final int VK_QCOM_RENDER_PASS_TRANSFORM_SPEC_VERSION

The extension specification version.

See Also:

• Constant Field Values

VK_QCOM_RENDER_PASS_TRANSFORM_EXTENSION_NAME

public static final String VK_QCOM_RENDER_PASS_TRANSFORM_EXTENSION_NAME

The extension name.

See Also:

• Constant Field Values

VK_STRUCTURE_TYPE_COMMAND_BUFFER_INHERITANCE_RENDER_PASS_TRANSFORM_INFO_QCOM

public static final int VK_STRUCTURE_TYPE_COMMAND_BUFFER_INHERITANCE_RENDER_PASS_TRANSFORM_INFO_QCOM

Extends VkStructureType.

Enum values:

• STRUCTURE_TYPE_COMMAND_BUFFER_INHERITANCE_RENDER_PASS_TRANSFORM_INFO_QCOM
• STRUCTURE_TYPE_RENDER_PASS_TRANSFORM_BEGIN_INFO_QCOM

See Also:

• Constant Field Values

VK_STRUCTURE_TYPE_RENDER_PASS_TRANSFORM_BEGIN_INFO_QCOM

public static final int VK_STRUCTURE_TYPE_RENDER_PASS_TRANSFORM_BEGIN_INFO_QCOM

Extends VkStructureType.

Enum values:

• STRUCTURE_TYPE_COMMAND_BUFFER_INHERITANCE_RENDER_PASS_TRANSFORM_INFO_QCOM
• STRUCTURE_TYPE_RENDER_PASS_TRANSFORM_BEGIN_INFO_QCOM

See Also:

• Constant Field Values

VK_RENDER_PASS_CREATE_TRANSFORM_BIT_QCOM

public static final int VK_RENDER_PASS_CREATE_TRANSFORM_BIT_QCOM

Extends VkRenderPassCreateFlagBits.

See Also:

• Constant Field Values