source/blender/gpu/vulkan/vk_context.cc

@@ -55,6 +55,7 @@ void VKContext::sync_backbuffer()
       command_buffer_.init(device);
       command_buffer_.begin_recording();
       device.init_dummy_buffer(*this);
+      device.init_dummy_color_attachment();
     }
     device.descriptor_pools_get().reset();
   }

source/blender/gpu/vulkan/vk_device.cc

@@ -27,6 +27,10 @@ void VKDevice::deinit()
   vkDestroyCommandPool(vk_device_, vk_command_pool_, vk_allocation_callbacks);
 
   dummy_buffer_.free();
+  if (dummy_color_attachment_.has_value()) {
+    delete &(*dummy_color_attachment_).get();
+    dummy_color_attachment_.reset();
+  }
   sampler_.free();
   destroy_discarded_resources();
   vmaDestroyAllocator(mem_allocator_);
@@ -135,6 +139,19 @@ void VKDevice::init_dummy_buffer(VKContext &context)
   dummy_buffer_.clear(context, 0);
 }
 
+void VKDevice::init_dummy_color_attachment()
+{
+  if (dummy_color_attachment_.has_value()) {
+    return;
+  }
+
+  GPUTexture *texture = GPU_texture_create_2d(
+      "dummy_attachment", 1, 1, 1, GPU_R32F, GPU_TEXTURE_USAGE_ATTACHMENT, nullptr);
+  BLI_assert(texture);
+  VKTexture &vk_texture = *unwrap(unwrap(texture));
+  dummy_color_attachment_ = std::make_optional(std::reference_wrapper(vk_texture));
+}
+
 /* -------------------------------------------------------------------- */
 /** \name Platform/driver/device information
  * \{ */

source/blender/gpu/vulkan/vk_device.hh

@@ -72,6 +72,7 @@ class VKDevice : public NonCopyable {
 
   /** Buffer to bind to unbound resource locations. */
   VKBuffer dummy_buffer_;
+  std::optional<std::reference_wrapper<VKTexture>> dummy_color_attachment_;
 
   Vector<std::pair<VkImage, VmaAllocation>> discarded_images_;
   Vector<std::pair<VkBuffer, VmaAllocation>> discarded_buffers_;
@@ -158,6 +159,7 @@ class VKDevice : public NonCopyable {
    * Dummy buffer can only be initialized after the command buffer of the context is retrieved.
    */
   void init_dummy_buffer(VKContext &context);
+  void init_dummy_color_attachment();
   void deinit();
 
   eGPUDeviceType device_type() const;
@@ -183,6 +185,12 @@ class VKDevice : public NonCopyable {
     return dummy_buffer_;
   }
 
+  VKTexture &dummy_color_attachment_get() const
+  {
+    BLI_assert(dummy_color_attachment_.has_value());
+    return (*dummy_color_attachment_).get();
+  }
+
   void discard_image(VkImage vk_image, VmaAllocation vma_allocation);
   void discard_image_view(VkImageView vk_image_view);
   void discard_buffer(VkBuffer vk_buffer, VmaAllocation vma_allocation);

source/blender/gpu/vulkan/vk_framebuffer.cc

@@ -413,6 +413,8 @@ void VKFrameBuffer::render_pass_create()
 
   bool has_depth_attachment = false;
   bool found_attachment = false;
+  const VKImageView &dummy_attachment =
+      VKBackend::get().device_get().dummy_color_attachment_get().image_view_get();
   int depth_location = -1;
 
   for (int type = GPU_FB_MAX_ATTACHMENT - 1; type >= 0; type--) {
@@ -436,8 +438,14 @@ void VKFrameBuffer::render_pass_create()
 
     int attachment_location = type >= GPU_FB_COLOR_ATTACHMENT0 ? type - GPU_FB_COLOR_ATTACHMENT0 :
                                                                  depth_location;
+    const bool is_depth_attachment = ELEM(
+        type, GPU_FB_DEPTH_ATTACHMENT, GPU_FB_DEPTH_STENCIL_ATTACHMENT);
 
     if (attachment.tex) {
+      BLI_assert_msg(!is_depth_attachment || !has_depth_attachment,
+                     "There can only be one depth/stencil attachment.");
+      has_depth_attachment |= is_depth_attachment;
+
       /* Ensure texture is allocated to ensure the image view. */
       VKTexture &texture = *static_cast<VKTexture *>(unwrap(attachment.tex));
       image_views_.append(VKImageView(texture,
@@ -461,18 +469,31 @@ void VKFrameBuffer::render_pass_create()
       attachment_description.finalLayout = texture.current_layout_get();
 
       /* Create the attachment reference. */
-      const bool is_depth_attachment = ELEM(
-          type, GPU_FB_DEPTH_ATTACHMENT, GPU_FB_DEPTH_STENCIL_ATTACHMENT);
-
-      BLI_assert_msg(!is_depth_attachment || !has_depth_attachment,
-                     "There can only be one depth/stencil attachment.");
-      has_depth_attachment |= is_depth_attachment;
       VkAttachmentReference &attachment_reference = attachment_references[attachment_location];
       attachment_reference.attachment = attachment_location;
       attachment_reference.layout = is_depth_attachment ?
                                         VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL :
                                         VK_IMAGE_LAYOUT_GENERAL;
     }
+    else if (!is_depth_attachment) {
+      image_views[attachment_location] = dummy_attachment.vk_handle();
+
+      VkAttachmentDescription &attachment_description =
+          attachment_descriptions[attachment_location];
+      attachment_description.flags = 0;
+      attachment_description.format = VK_FORMAT_R32_SFLOAT;
+      attachment_description.samples = VK_SAMPLE_COUNT_1_BIT;
+      attachment_description.loadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
+      attachment_description.storeOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
+      attachment_description.stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
+      attachment_description.stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
+      attachment_description.initialLayout = VK_IMAGE_LAYOUT_GENERAL;
+      attachment_description.finalLayout = VK_IMAGE_LAYOUT_GENERAL;
+
+      VkAttachmentReference &attachment_reference = attachment_references[attachment_location];
+      attachment_reference.attachment = VK_ATTACHMENT_UNUSED;
+      attachment_reference.layout = VK_IMAGE_LAYOUT_UNDEFINED;
+    }
   }
 
   /* Update the size, viewport & scissor based on the first attachment. */
@@ -492,7 +513,6 @@ void VKFrameBuffer::render_pass_create()
   scissor_reset();
 
   /* Create render pass. */
-
   const int attachment_len = has_depth_attachment ? depth_location + 1 : depth_location;
   const int color_attachment_len = depth_location;
   VkSubpassDescription subpass = {};
@@ -594,6 +614,17 @@ void VKFrameBuffer::update_size()
   size_set(1, 1);
 }
 
+int VKFrameBuffer::color_attachments_resource_size() const
+{
+  int size = 0;
+  for (int color_slot : IndexRange(GPU_FB_MAX_COLOR_ATTACHMENT)) {
+    if (color_tex(color_slot) != nullptr) {
+      size = max_ii(color_slot + 1, size);
+    }
+  }
+  return size;
+}
+
 /** \} */
 
 }  // namespace blender::gpu

source/blender/gpu/vulkan/vk_framebuffer.hh

@@ -109,6 +109,15 @@ class VKFrameBuffer : public FrameBuffer {
    */
   void update_size();
 
+  /**
+   * Return the number of color attachments of this frame buffer, including unused color
+   * attachments.
+   *
+   * Framebuffers can have unused attachments. When higher attachment slots are being used, unused
+   * lower attachment slots will be counted as they are required resources in renderpasses.
+   */
+  int color_attachments_resource_size() const;
+
  private:
   void update_attachments();
   void render_pass_free();

source/blender/gpu/vulkan/vk_pipeline_state.cc

@@ -78,13 +78,8 @@ void VKPipelineStateManager::force_state(const GPUState &state,
 void VKPipelineStateManager::finalize_color_blend_state(const VKFrameBuffer &framebuffer)
 {
   color_blend_attachments.clear();
-  for (int color_slot = 0; color_slot < GPU_FB_MAX_COLOR_ATTACHMENT; color_slot++) {
-    VKTexture *texture = unwrap(unwrap(framebuffer.color_tex(color_slot)));
-    if (texture) {
-      color_blend_attachments.append(color_blend_attachment_template);
-    }
-  }
-
+  color_blend_attachments.append_n_times(color_blend_attachment_template,
+                                         framebuffer.color_attachments_resource_size());
   pipeline_color_blend_state.attachmentCount = color_blend_attachments.size();
   pipeline_color_blend_state.pAttachments = color_blend_attachments.data();
 }