GFSDK_HBAO+_distro_r3.0_cl20573789

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+.. Replace existing content with product specific content. Layout for this page should be consistent for all products. 
+
+|PRODUCTNAME| |VERSION|
+======================================
+
+.. Replace the content. Layout should not change
+
+Overview
+##############
+HBAO+ is a SSAO algorithm designed to achieve high GPU efficiency.
+The algorithm is based on HBAO [Bavoil and Sainz 2008], with the following differences:
+
+#. To minimize cache trashing, HBAO+ does not use any randomization texture. Instead, the algorithm uses an Interleaved Rendering approach, generating the AO in multiple passes with a unique jitter value per pass [Bavoil and Jansen 2013].
+
+#. To avoid over-occlusion artifacts, HBAO+ uses a simpler AO approximation than HBAO, similar to "Scalable Ambient Obscurance" [McGuire et al. 2012] [Bukowski et al. 2012].
+
+#. To minimize flickering, the HBAO+ is always rendered in full resolution, from full-resolution depths.
+
+
+.. image:: \_static\hbao-plus-in-tom-clancys-splinter-cell-blacklist-2.jpg
+
+Package
+##############
+
+``doc/``\—this documentation page.
+
+``lib/``\—header file, import libraries and DLLs, for Win32, Win64, Mac OS X and Linux.
+
+``samples/``\—source for sample applications demonstrating NVIDIA HBAO+.
+
+Getting Started
+###############
+
+#. INITIALIZE THE LIBRARY::
+
+    GFSDK_SSAO_CustomHeap CustomHeap;
+    CustomHeap.new_ = ::operator new;
+    CustomHeap.delete_ = ::operator delete;
+
+    GFSDK_SSAO_Status status;
+    GFSDK_SSAO_Context_D3D11* pAOContext;
+    status = GFSDK_SSAO_CreateContext_D3D11(pD3D11Device, &pAOContext, &CustomHeap);
+    assert(status == GFSDK_SSAO_OK); // HBAO+ requires feature level 11_0 or above
+
+#. SET INPUT DEPTHS::
+
+    GFSDK_SSAO_InputData_D3D11 Input;
+    Input.DepthData.DepthTextureType = GFSDK_SSAO_HARDWARE_DEPTHS;
+    Input.DepthData.pFullResDepthTextureSRV = pDepthStencilTextureSRV;
+    Input.DepthData.ProjectionMatrix.Data = GFSDK_SSAO_Float4x4(pProjectionMatrix);
+    Input.DepthData.ProjectionMatrix.Layout = GFSDK_SSAO_ROW_MAJOR_ORDER;
+    Input.DepthData.MetersToViewSpaceUnits = SceneScale;
+
+#. SET AO PARAMETERS::
+
+    GFSDK_SSAO_Parameters_D3D11 Params;
+    Params.Radius = 2.f;
+    Params.Bias = 0.1f;
+    Params.PowerExponent = 2.f;
+    Params.Blur.Enable = true;
+    Params.Blur.Radius = GFSDK_SSAO_BLUR_RADIUS_4;
+    Params.Blur.Sharpness = 16.f;
+
+#. SET RENDER TARGET::
+
+    GFSDK_SSAO_Output_D3D11 Output;
+    Output.pRenderTargetView = pOutputColorRTV;
+    Output.Blend.Mode = GFSDK_SSAO_OVERWRITE_RGB;
+
+#. RENDER AO::
+
+    status = pAOContext->RenderAO(pD3D11Context, Input, Params, Output);
+    assert(status == GFSDK_SSAO_OK);
+	
+Data Flow
+#############
+	
+Input Requirements
+++++++++++++++++++++
+
+* The library has entry points for D3D11, D3D12 and GL3.2+.
+
+* Requires a depth texture to be provided as input, along with associated projection info.
+
+* Optionally, can also take as input a GBuffer normal texture associated with the input depth texture:
+
+  * Can add normal-mapping details to the AO.
+
+  * Can be used to fix normal reconstruction artifacts with dithered LOD dissolves.
+
+  * But makes the integration more complex. We recommend starting with input normals disabled.
+
+* Optionally, can also take as input a viewport rectangle associated with the input textures:
+
+  * Defines a sub-area of the input & output full-resolution textures to be sourced and rendered to.
+
+  * The library re-allocates its internal render targets if the Viewport.Width or Viewport.Height changes for a given AO context.
+
+MSAA Support
+++++++++++++++++++++
+
+* Requirements
+
+  * The input depth & normal textures are required to have matching dimensions and MSAA sample count.
+
+  * The output render target can have arbitrary dimensions and MSAA sample count.
+
+* Per-Pixel AO Algorithm
+
+  * If the input textures are MSAA, only sample 0 is used to render the AO.
+
+  * If the output render target is MSAA, a per-pixel AO value is written to all samples.
+
+  * In practice, we have found this strategy to not cause any objectionable artifacts, even when using HBAO+ with TXAA.
+
+HBAO+ Pipeline
+++++++++++++++++++++
+
+.. image:: \_static\pipeline_without_input_normals.png
+
+.. image:: \_static\pipeline_with_input_normals.png
+
+Occlusion Samples
+++++++++++++++++++++
+
+* For each pixel, 32 occlusion samples are taken in a variable-radius disk, with a minimum of 4 full-resolution pixels between the center pixel and the sample coordinates.
+
+* The 8 nearest samples to the center pixel are weighted by the NearAO parameter.
+
+* The other samples are weighted by the FarAO parameter.
+
+Parameters
+##########
+
+AO Radius
+++++++++++++++++++++
+
+Definition
+ For a given AO receiver point P and AO Radius R, sample point S is ignored if ||P-S|| > R
+
+Impact on search area
+ The AO radius is a multiplier for the screen-space search radius, and the number of samples is fixed. So if the AO radius is too large, under-sampling artifacts may appear.
+
+.. image:: \_static\AO_Radius_1.png
+
+.. image:: \_static\AO_Radius_4.png
+
+MetersToViewSpaceUnits
+++++++++++++++++++++++++++++++++++
+
+If you are not sure what to set this value to, you can:
+
+* Set the ``AO Radius`` parameter to 1.0 and
+
+* Increase ``MetersToViewSpaceUnits`` until the AO looks like it's being cast up to 1 meter away
+
+``MetersToViewSpaceUnits`` is used internally
+
+* To convert the AO radius parameter from meters to view-space units
+
+* To adjust the blur sharpness parameter
+
+Power Exponent
+++++++++++++++++++++
+
+* The PowerExponent parameter controls the darkness of the final AO: FinalAO = pow(AO, PowerExponent).
+
+* Typical PowerExponent values are in the range [2.0, 3.0].
+
+AO Bias
+++++++++++++++++++++
+
+* The AO Bias parameter can be used to hide low-tessellation artifacts
+
+* Can also help reducing false-occlusion artifacts near screen borders
+
+* It weights the AO contributions more strongly for samples towards the normal direction
+
+.. image:: \_static\AOBias_0_0.png 
+
+.. image:: \_static\AOBias_0_3.png 
+
+Foreground AO
+++++++++++++++++++++
+
+* When this feature is enabled, the screen-space AO kernel radius is:
+
+  * inversely proportional to ViewDepth for ViewDepth > ForegroundViewDepth
+
+  * uniform in screen-space for ViewDepth <= ForegroundViewDepth (instead of getting arbitrarily large)
+
+* To tune the ForegroundViewDepth parameter
+
+  * Start with ForegroundViewDepth = 0.f
+
+  * Increase the ForegroundViewDepth to get less closer-scale occlusion on the foreground objects.
+
+.. image:: \_static\ForegroundAO_OFF.png
+
+.. image:: \_static\ForegroundAO_ON.png
+
+Background AO
+++++++++++++++++++++
+
+* When this feature is enabled, the screen-space AO kernel radius is:
+
+  * inversely proportional to ViewDepth for ViewDepth < BackgroundViewDepth
+
+  * uniform in screen-space for ViewDepth >= BackgroundViewDepth (instead of falling off to zero).
+
+* To tune the BackgroundViewDepth parameter
+
+  * Start from a very large BackgroundViewDepth value (e.g. the camera's ZFar)
+
+  * Decrease the BackgroundViewDepth to get larger-scale occlusion in the background.
+
+.. image:: \_static\BackgroundAO_OFF.png
+
+.. image:: \_static\BackgroundAO_ON.png
+
+AO Blur
+++++++++++++++++++++
+
+* Optional cross-bilateral filter
+
+  * To remove jittered-sampling artifacts (noise)
+  
+  * To hide under-sampling artifacts (banding) & reduce jittering
+  
+* 3 Modes
+
+  * No Blur
+  
+  * Blur Radius 2
+  
+  * Blur Radius 4
+  
+.. image:: \_static\No_Blur.png   
+
+.. image:: \_static\Blur_Radius_4.png 
+
+Blur Sharpness
+++++++++++++++++++++
+
+The greater the sharpness parameter, the more the blur preserves edges
+
+.. image:: \_static\Blur_Sharpness_0.png 
+
+.. image:: \_static\Blur_Sharpness_8.png  
+
+Integration Time Estimates
+##########################
+
+* Initial integration (for a rendering engineer)
+
+  * <1 man-day with no input normals
+
+  * 1-2 man-days with input normals
+  
+* Initial parameter tuning
+
+  * <1 man-hour
+  
+  * Tuning the parameter should be quick once the input data are correctly fed into the library
+  
+  * The same HBAO+ parameters may be used globally across the whole game
+
+Additional Links
+################
+
+`[Bavoil et al. 2008] "Image-Space Horizon-Based Ambient Occlusion" <http://www.nvidia.com/object/siggraph-2008-HBAO.html>`_
+
+`[McGuire et al. 2012] "Scalable Ambient Obscurance" <http://graphics.cs.williams.edu/papers/SAOHPG12/>`_
+
+`[Bukowski et al. 2012] "Scalable High-Quality Motion Blur and Ambient Occlusion" <http://graphics.cs.williams.edu/papers/VVSIGGRAPH12/>`_
+
+`[Bavoil and Jansen 2013] "Particle Shadows & Cache-Efficient Post-Processing" <https://developer.nvidia.com/gdc-2013>`_
+
+
+.. Un-comment out if section is used
+.. Additional Links
+.. ################   
+
+.. Possible content here includes any of the following:
+.. * User guide
+.. * Videos
+.. * Forums
+.. * Etc.
+
+.. toctree::
+   :maxdepth: 1
+
+.. Example of Getting Start Guide link
+.. _Getting Started Guide: gettingstarted.html