public class NVClipSpaceWScaling
extends java.lang.Object
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.
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);
}VK_NV_clip_space_w_scaling| Modifier and Type | Field and Description |
|---|---|
static int |
VK_DYNAMIC_STATE_VIEWPORT_W_SCALING_NV
Extends
VkDynamicState. |
static java.lang.String |
VK_NV_CLIP_SPACE_W_SCALING_EXTENSION_NAME
The extension name.
|
static int |
VK_NV_CLIP_SPACE_W_SCALING_SPEC_VERSION
The extension specification version.
|
static int |
VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_W_SCALING_STATE_CREATE_INFO_NV
Extends
VkStructureType. |
| Modifier and Type | Method and Description |
|---|---|
static void |
nvkCmdSetViewportWScalingNV(org.lwjgl.vulkan.VkCommandBuffer commandBuffer,
int firstViewport,
int viewportCount,
long pViewportWScalings)
Unsafe version of:
CmdSetViewportWScalingNV |
static void |
vkCmdSetViewportWScalingNV(org.lwjgl.vulkan.VkCommandBuffer commandBuffer,
int firstViewport,
VkViewportWScalingNV.Buffer pViewportWScalings)
Set the viewport W scaling on a command buffer.
|
public static final int VK_NV_CLIP_SPACE_W_SCALING_SPEC_VERSION
public static final java.lang.String VK_NV_CLIP_SPACE_W_SCALING_EXTENSION_NAME
public static final int VK_STRUCTURE_TYPE_PIPELINE_VIEWPORT_W_SCALING_STATE_CREATE_INFO_NV
VkStructureType.public static final int VK_DYNAMIC_STATE_VIEWPORT_W_SCALING_NV
VkDynamicState.public static void nvkCmdSetViewportWScalingNV(org.lwjgl.vulkan.VkCommandBuffer commandBuffer,
int firstViewport,
int viewportCount,
long pViewportWScalings)
CmdSetViewportWScalingNVviewportCount - the number of viewports whose parameters are updated by the command.public static void vkCmdSetViewportWScalingNV(org.lwjgl.vulkan.VkCommandBuffer commandBuffer,
int firstViewport,
VkViewportWScalingNV.Buffer pViewportWScalings)
If the bound pipeline state object was not created with the DYNAMIC_STATE_VIEWPORT_W_SCALING_NV dynamic state enabled, viewport W scaling parameters are specified using the pViewportWScalings member of VkPipelineViewportWScalingStateCreateInfoNV in the pipeline state object. If the pipeline state object was created with the DYNAMIC_STATE_VIEWPORT_W_SCALING_NV dynamic state enabled, the viewport transformation parameters are dynamically set and changed with the command:
void vkCmdSetViewportWScalingNV(
VkCommandBuffer commandBuffer,
uint32_t firstViewport,
uint32_t viewportCount,
const VkViewportWScalingNV* pViewportWScalings);The viewport parameters taken from element i of pViewportWScalings replace the current state for the viewport index firstViewport + i, for i in [0, viewportCount).
DYNAMIC_STATE_VIEWPORT_W_SCALING_NV dynamic state enabledfirstViewport must be less than VkPhysicalDeviceLimits::maxViewportsfirstViewport and viewportCount must be between 1 and VkPhysicalDeviceLimits::maxViewports, inclusivecommandBuffer must be a valid VkCommandBuffer handlepViewportWScalings must be a valid pointer to an array of viewportCount VkViewportWScalingNV structurescommandBuffer must be in the recording stateVkCommandPool that commandBuffer was allocated from must support graphics operationsviewportCount must be greater than 0commandBuffer must be externally synchronizedVkCommandPool that commandBuffer was allocated from must be externally synchronized| Command Buffer Levels | Render Pass Scope | Supported Queue Types | Pipeline Type |
|---|---|---|---|
| Primary Secondary | Both | Graphics |
commandBuffer - the command buffer into which the command will be recorded.firstViewport - the index of the first viewport whose parameters are updated by the command.pViewportWScalings - a pointer to an array of VkViewportWScalingNV structures specifying viewport parameters.Copyright LWJGL. All Rights Reserved. License terms.