Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell2010 |
Name
VK_NV_clip_space_w_scaling - device extension
VK_NV_clip_space_w_scaling
- Name String
VK_NV_clip_space_w_scaling
- Extension Type
- Device extension
- Registered Extension Number
- 88
- Revision
- 1
- Ratification Status
- Not ratified
- Extension and Version Dependencies; Contact
Other Extension Metadata
- Last Modified Date
- 2017-02-15
- Contributors
- Eric Werness, NVIDIA
- Kedarnath Thangudu, NVIDIA
Description
Virtual Reality (VR) applications often involve a post-processing step to apply a “barrel” distortion to the rendered image to correct the “pincushion” distortion introduced by the optics in a VR device. The barrel distorted image has lower resolution along the edges compared to the center. Since the original image is rendered at high resolution, which is uniform across the complete image, a lot of pixels towards the edges do not make it to the final post-processed image.
This extension provides a mechanism to render VR scenes at a non-uniform resolution, in particular a resolution that falls linearly from the center towards the edges. This is achieved by scaling the w coordinate of the vertices in the clip space before perspective divide. The clip space w coordinate of the vertices can be offset as of a function of x and y coordinates as follows:
w' = w + Ax + By
In the intended use case for viewport position scaling, an application should use a set of four viewports, one for each of the four quadrants of a Cartesian coordinate system. Each viewport is set to the dimension of the image, but is scissored to the quadrant it represents. The application should specify A and B coefficients of the w-scaling equation above, that have the same value, but different signs, for each of the viewports. The signs of A and B should match the signs of x and y for the quadrant that they represent such that the value of w' will always be greater than or equal to the original w value for the entire image. Since the offset to w, (Ax + By), is always positive, and increases with the absolute values of x and y, the effective resolution will fall off linearly from the center of the image to its edges.
New Commands
New Structures
New Enum Constants
NV_CLIP_SPACE_W_SCALING_SPEC_VERSION
Extending
DynamicState
:Extending
StructureType
:
Issues
1) Is the pipeline struct name too long?
RESOLVED: It fits with the naming convention.
2) Separate W scaling section or fold into coordinate transformations?
RESOLVED: Leaving it as its own section for now.
Examples
VkViewport viewports[4]; VkRect2D scissors[4]; VkViewportWScalingNV scalings[4]; for (int i = 0; i < 4; i++) { int x = (i & 2) ? 0 : currentWindowWidth / 2; int y = (i & 1) ? 0 : currentWindowHeight / 2; viewports[i].x = 0; viewports[i].y = 0; viewports[i].width = currentWindowWidth; viewports[i].height = currentWindowHeight; viewports[i].minDepth = 0.0f; viewports[i].maxDepth = 1.0f; scissors[i].offset.x = x; scissors[i].offset.y = y; scissors[i].extent.width = currentWindowWidth/2; scissors[i].extent.height = currentWindowHeight/2; const float factor = 0.15; scalings[i].xcoeff = ((i & 2) ? -1.0 : 1.0) * factor; scalings[i].ycoeff = ((i & 1) ? -1.0 : 1.0) * factor; } VkPipelineViewportWScalingStateCreateInfoNV vpWScalingStateInfo = { VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_W_SCALING_STATE_CREATE_INFO_NV }; vpWScalingStateInfo.viewportWScalingEnable = VK_TRUE; vpWScalingStateInfo.viewportCount = 4; vpWScalingStateInfo.pViewportWScalings = &scalings[0]; VkPipelineViewportStateCreateInfo vpStateInfo = { VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_STATE_CREATE_INFO }; vpStateInfo.viewportCount = 4; vpStateInfo.pViewports = &viewports[0]; vpStateInfo.scissorCount = 4; vpStateInfo.pScissors = &scissors[0]; vpStateInfo.pNext = &vpWScalingStateInfo;
Example shader to read from a w-scaled texture:
// Vertex Shader // Draw a triangle that covers the whole screen const vec4 positions[3] = vec4[3](vec4(-1, -1, 0, 1), vec4( 3, -1, 0, 1), vec4(-1, 3, 0, 1)); out vec2 uv; void main() { vec4 pos = positions[ gl_VertexID ]; gl_Position = pos; uv = pos.xy; } // Fragment Shader uniform sampler2D tex; uniform float xcoeff; uniform float ycoeff; out vec4 Color; in vec2 uv; void main() { // Handle uv as if upper right quadrant vec2 uvabs = abs(uv); // unscale: transform w-scaled image into an unscaled image // scale: transform unscaled image int a w-scaled image float unscale = 1.0 / (1 + xcoeff * uvabs.x + xcoeff * uvabs.y); //float scale = 1.0 / (1 - xcoeff * uvabs.x - xcoeff * uvabs.y); vec2 P = vec2(unscale * uvabs.x, unscale * uvabs.y); // Go back to the right quadrant P *= sign(uv); Color = texture(tex, P * 0.5 + 0.5); }
Version History
Revision 1, 2017-02-15 (Eric Werness)
- Internal revisions
See Also
PipelineViewportWScalingStateCreateInfoNV
, ViewportWScalingNV
,
cmdSetViewportWScalingNV
Document Notes
For more information, see the Vulkan Specification
This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.
Synopsis
- cmdSetViewportWScalingNV :: forall io. MonadIO io => CommandBuffer -> ("firstViewport" ::: Word32) -> ("viewportWScalings" ::: Vector ViewportWScalingNV) -> io ()
- data ViewportWScalingNV = ViewportWScalingNV {}
- data PipelineViewportWScalingStateCreateInfoNV = PipelineViewportWScalingStateCreateInfoNV {}
- type NV_CLIP_SPACE_W_SCALING_SPEC_VERSION = 1
- pattern NV_CLIP_SPACE_W_SCALING_SPEC_VERSION :: forall a. Integral a => a
- type NV_CLIP_SPACE_W_SCALING_EXTENSION_NAME = "VK_NV_clip_space_w_scaling"
- pattern NV_CLIP_SPACE_W_SCALING_EXTENSION_NAME :: forall a. (Eq a, IsString a) => a
Documentation
cmdSetViewportWScalingNV Source #
:: forall io. MonadIO io | |
=> CommandBuffer |
|
-> ("firstViewport" ::: Word32) |
|
-> ("viewportWScalings" ::: Vector ViewportWScalingNV) |
|
-> io () |
vkCmdSetViewportWScalingNV - Set the viewport W scaling dynamically for a command buffer
Description
The viewport parameters taken from element i of pViewportWScalings
replace the current state for the viewport index firstViewport
+ i,
for i in [0, viewportCount
).
This command sets the viewport W scaling for subsequent drawing
commands when drawing using
shader objects,
or when the graphics pipeline is created with
DYNAMIC_STATE_VIEWPORT_W_SCALING_NV
set in
PipelineDynamicStateCreateInfo
::pDynamicStates
.
Otherwise, this state is specified by the
PipelineViewportWScalingStateCreateInfoNV
::pViewportWScalings
values
used to create the currently active pipeline.
Valid Usage
- The sum of
firstViewport
andviewportCount
must be between1
andPhysicalDeviceLimits
::maxViewports
, inclusive
Valid Usage (Implicit)
-
commandBuffer
must be a validCommandBuffer
handle
-
pViewportWScalings
must be a valid pointer to an array ofviewportCount
ViewportWScalingNV
structures -
commandBuffer
must be in the recording state - The
CommandPool
thatcommandBuffer
was allocated from must support graphics operations - This command must only be called outside of a video coding scope
-
viewportCount
must be greater than0
Host Synchronization
- Host access to
commandBuffer
must be externally synchronized
- Host access to the
CommandPool
thatcommandBuffer
was allocated from must be externally synchronized
Command Properties
'
Command Buffer Levels | Render Pass Scope | Video Coding Scope | Supported Queue Types | Command Type |
---|---|---|---|---|
Primary Secondary | Both | Outside | Graphics | State |
See Also
VK_NV_clip_space_w_scaling,
CommandBuffer
, ViewportWScalingNV
data ViewportWScalingNV Source #
VkViewportWScalingNV - Structure specifying a viewport
See Also
VK_NV_clip_space_w_scaling,
PipelineViewportWScalingStateCreateInfoNV
, cmdSetViewportWScalingNV
Instances
data PipelineViewportWScalingStateCreateInfoNV Source #
VkPipelineViewportWScalingStateCreateInfoNV - Structure specifying parameters of a newly created pipeline viewport W scaling state
Valid Usage (Implicit)
See Also
VK_NV_clip_space_w_scaling,
Bool32
,
StructureType
, ViewportWScalingNV
PipelineViewportWScalingStateCreateInfoNV | |
|
Instances
type NV_CLIP_SPACE_W_SCALING_SPEC_VERSION = 1 Source #
pattern NV_CLIP_SPACE_W_SCALING_SPEC_VERSION :: forall a. Integral a => a Source #
type NV_CLIP_SPACE_W_SCALING_EXTENSION_NAME = "VK_NV_clip_space_w_scaling" Source #
pattern NV_CLIP_SPACE_W_SCALING_EXTENSION_NAME :: forall a. (Eq a, IsString a) => a Source #