VideoBackends: add support to allow rendering to multiple output textures

Source/Core/VideoCommon/AbstractFramebuffer.cpp

@@ -6,10 +6,12 @@
 
 AbstractFramebuffer::AbstractFramebuffer(AbstractTexture* color_attachment,
                                          AbstractTexture* depth_attachment,
+                                         std::vector<AbstractTexture*> additional_color_attachments,
                                          AbstractTextureFormat color_format,
                                          AbstractTextureFormat depth_format, u32 width, u32 height,
                                          u32 layers, u32 samples)
     : m_color_attachment(color_attachment), m_depth_attachment(depth_attachment),
+      m_additional_color_attachments(std::move(additional_color_attachments)),
       m_color_format(color_format), m_depth_format(depth_format), m_width(width), m_height(height),
       m_layers(layers), m_samples(samples)
 {
@@ -17,13 +19,18 @@ AbstractFramebuffer::AbstractFramebuffer(AbstractTexture* color_attachment,
 
 AbstractFramebuffer::~AbstractFramebuffer() = default;
 
-bool AbstractFramebuffer::ValidateConfig(const AbstractTexture* color_attachment,
-                                         const AbstractTexture* depth_attachment)
+bool AbstractFramebuffer::ValidateConfig(
+    const AbstractTexture* color_attachment, const AbstractTexture* depth_attachment,
+    const std::vector<AbstractTexture*>& additional_color_attachments)
 {
   // Must have at least a color or depth attachment.
   if (!color_attachment && !depth_attachment)
     return false;
 
+  // Must have a color attachment if additional color attachments are defined
+  if (!color_attachment && !additional_color_attachments.empty())
+    return false;
+
   // Currently we only expose a single mip level for render target textures.
   // MSAA textures are not supported with mip levels on most backends, and it simplifies our
   // handling of framebuffers.
@@ -36,6 +43,14 @@ bool AbstractFramebuffer::ValidateConfig(const AbstractTexture* color_attachment
     return false;
   }
 
+  for (auto* attachment : additional_color_attachments)
+  {
+    if (!CheckAttachment(attachment))
+    {
+      return false;
+    }
+  }
+
   // If both color and depth are present, their attributes must match.
   if (color_attachment && depth_attachment)
   {
@@ -48,6 +63,16 @@ bool AbstractFramebuffer::ValidateConfig(const AbstractTexture* color_attachment
     }
   }
 
+  for (auto* attachment : additional_color_attachments)
+  {
+    if (color_attachment->GetConfig().width != attachment->GetConfig().width ||
+        color_attachment->GetConfig().height != attachment->GetConfig().height ||
+        color_attachment->GetConfig().samples != attachment->GetConfig().samples)
+    {
+      return false;
+    }
+  }
+
   return true;
 }
 

Source/Core/VideoCommon/AbstractFramebuffer.h

@@ -3,6 +3,8 @@
 
 #pragma once
 
+#include <vector>
+
 #include "Common/CommonTypes.h"
 #include "Common/MathUtil.h"
 #include "VideoCommon/TextureConfig.h"
@@ -18,12 +20,14 @@ class AbstractFramebuffer
 {
 public:
   AbstractFramebuffer(AbstractTexture* color_attachment, AbstractTexture* depth_attachment,
+                      std::vector<AbstractTexture*> additional_color_attachments,
                       AbstractTextureFormat color_format, AbstractTextureFormat depth_format,
                       u32 width, u32 height, u32 layers, u32 samples);
   virtual ~AbstractFramebuffer();
 
   static bool ValidateConfig(const AbstractTexture* color_attachment,
-                             const AbstractTexture* depth_attachment);
+                             const AbstractTexture* depth_attachment,
+                             const std::vector<AbstractTexture*>& additional_color_attachments);
 
   AbstractTexture* GetColorAttachment() const { return m_color_attachment; }
   AbstractTexture* GetDepthAttachment() const { return m_depth_attachment; }
@@ -42,6 +46,7 @@ protected:
   AbstractTexture* m_depth_attachment;
   AbstractTextureFormat m_color_format;
   AbstractTextureFormat m_depth_format;
+  std::vector<AbstractTexture*> m_additional_color_attachments;
   u32 m_width;
   u32 m_height;
   u32 m_layers;

Source/Core/VideoCommon/AbstractGfx.h

@@ -10,6 +10,7 @@
 
 #include <array>
 #include <memory>
+#include <vector>
 
 class AbstractFramebuffer;
 class AbstractPipeline;
@@ -75,7 +76,8 @@ public:
   virtual std::unique_ptr<AbstractStagingTexture>
   CreateStagingTexture(StagingTextureType type, const TextureConfig& config) = 0;
   virtual std::unique_ptr<AbstractFramebuffer>
-  CreateFramebuffer(AbstractTexture* color_attachment, AbstractTexture* depth_attachment) = 0;
+  CreateFramebuffer(AbstractTexture* color_attachment, AbstractTexture* depth_attachment,
+                    std::vector<AbstractTexture*> additional_color_attachments = {}) = 0;
 
   // Framebuffer operations.
   virtual void SetFramebuffer(AbstractFramebuffer* framebuffer);

Source/Core/VideoCommon/RenderState.cpp

@@ -453,6 +453,7 @@ FramebufferState GetColorFramebufferState(AbstractTextureFormat format)
   state.depth_texture_format = AbstractTextureFormat::Undefined;
   state.per_sample_shading = false;
   state.samples = 1;
+  state.additional_color_attachment_count = 0;
   return state;
 }
 

Source/Core/VideoCommon/RenderState.h

@@ -80,6 +80,12 @@ union FramebufferState
   BitField<16, 8, u32> samples;
   BitField<24, 1, u32> per_sample_shading;
 
+  // Note: all additional color attachments
+  // have the same format as `color_texture_format`
+  // TODO: in the future improve this so every attachment
+  // can specify its own format
+  BitField<25, 3, u32> additional_color_attachment_count;
+
   u32 hex = 0;
 };