Add global uniform buffer support with vhGlobalUniform struct

Author: hypernewbie

src/vrhi_backend.cpp

@@ -1028,13 +1028,40 @@ void vhCmdBackendState::BE_BlitBuffer( vhBackendBuffer& dst, vhBackendBuffer& sr
 void vhCmdBackendState::init()
 {
     std::lock_guard< std::mutex > lock( backendMutex );
+
+    if ( !m_globalUniformBuffer )
+    {
+        // Called from vhInit which already holds g_nvRHIStateMutex lock, and before RHI thread even starts.
+        // So we don't need to lock g_nvRHIStateMutex here.
+    
+        nvrhi::BufferDesc desc;
+        desc.setByteSize( sizeof( vhGlobalUniform ) );
+        desc.setIsConstantBuffer( true );
+        desc.setDebugName( "GlobalUniforms" );
+        nvrhi::BufferHandle bhandle = g_vhDevice->createBuffer( desc );
+        if ( !bhandle ) 
+        {
+            VRHI_ERR( "vhCmdBackendState::init() : Failed to create Global Uniform Buffer!\n" );
+            assert( !"Failed to create Global Uniform Buffer." );
+            return;
+        }
+
+        m_globalUniformBuffer = std::make_unique< vhBackendBuffer >();
+        m_globalUniformBuffer->handle = bhandle;
+        m_globalUniformBuffer->name = "GlobalUniforms";
+        m_globalUniformBuffer->desc = desc;
+        m_globalUniformBuffer->stride = sizeof( vhGlobalUniform );
+        m_globalUniformBuffer->flags = VRHI_BUFFER_NONE;
+    }
 }
 
 void vhCmdBackendState::shutdown()
 {
     std::lock_guard< std::mutex > lock( backendMutex );
     std::lock_guard< std::mutex > lock2( g_nvRHIStateMutex );
 
+    m_globalUniformBuffer.reset();
+
     backendTextures.clear();
     backendBuffers.clear();
     backendShaders.clear();

src/vrhi_backend.h

@@ -120,6 +120,25 @@ struct vhStateResolveCache
 // Main Backend State
 // --------------------------------------------------------------------------
 
+struct vhGlobalUniform
+{
+    glm::vec4 u_viewRect;
+    glm::vec4 u_viewTexel;
+    glm::mat4 u_view;
+    glm::mat4 u_invView;
+    glm::mat4 u_proj;
+    glm::mat4 u_invProj;
+    glm::mat4 u_viewProj;
+    glm::mat4 u_invViewProj;
+    glm::mat4 u_model[4];
+    glm::mat4 u_modelView;
+    glm::mat4 u_modelViewProj;
+    glm::vec4 u_alphaRef4;
+    glm::vec4 u_global[32];
+};
+static_assert( sizeof( vhGlobalUniform ) < 16384, "vhGlobalUniform must be smaller than 16KB" );
+static_assert( sizeof( vhGlobalUniform ) == 1328, "vhGlobalUniform packing mismatch" );
+
 class vhCmdBackendState : public VIDLHandler
 {
     friend class vhCmdBackendStateTest;
@@ -132,6 +151,8 @@ class vhCmdBackendState : public VIDLHandler
     std::map< vhStateId, vhState > backendStates;
     std::unordered_map< uint64_t, nvrhi::FramebufferHandle > backendFramebuffers;
 
+    // Internal Global Uniform Buffer
+    std::unique_ptr< vhBackendBuffer > m_globalUniformBuffer;
     // RAII for vhMem, takes ownership of the pointer and auto-destructs it.
     inline std::unique_ptr< vhMem > BE_MemRAII( const vhMem* mem )
     {