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+# HBAOPlus
+NVIDIA HBAO+ 3.0.
+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.
+
+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.