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Graphics API Debugger

The state of rendering of Vulkan applications is reflected in two parts in GAPID:

  • Command pane: Submitted commands grouped by renderpass and subpasses.
  • State pane: Bound resources, framebuffers, renderpasses, etc.

Command grouping

Under a expanded vkQueueSubmit command, the submitted command buffer commands are grouped in the command pane according to submission batches and command buffers. An expanded vkQueueSubmit with drawing commands in it will looks like the image below.

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Vulkan commands

  1. Renderpass groups: Submitted commands between vkCmdBeginRenderPass and vkCmdEndRenderPass (inclusive) are grouped in a renderpass group. The group will be named with the renderpass name if the renderpass has been assigned a name, the otherwise the value of the VkRenderPass will used as the name, as shown in the image above.

  2. Subpass groups: Submitted commands divided by vkCmdNextSubpass will be grouped into corresponding subpass groups. Subpass groups will be skipped if the renderpass contains only one subpass, otherwise the subpass groups will be added under the renderpass group, named with the subpass number. Each subpass group ends with either vkCmdNextSubpass or vkCmdEndRenderPass.

Drawing information

To check the render state after a specific submitted command, click the command in question in command pane, the render state can be examed in the following items in the state pane.

Last bound queue (currently bound queue)

The LastBoundQueue node contains the information of the queue used for the vkQueueSubmit, which submits the command in question. The VulkanHandle will be used to find the drawing information of the current render state in LastDrawInfos.

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  1. The VulkanHandle shows the value of the last used VkQueue, which is actually the currently bound queue for the submitted command in question.

  2. The information of the current render state is stored in LastDrawInfos, indexed by VkQueue value.

Last draw infos (current render state info)

LastDrawInfos contains the information of the last drawing for each VkQueue, includes Framebuffer info, renderpass info, Bound descriptor sets, Bound vertex/index buffers, Graphics pipeline and drawing parameters.

Bound framebuffer

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  1. Framebuffer node shows the info of the currently bound framebuffer. This node gets updated after each vkCmdBeginRenderPass executes on the same queue.

  2. Renderpass node shows the info of the renderpass used to create the framebuffer. Note that this is not the renderpass currently bound for drawing.

  3. ImageAttachments node lists all the image attachments (VkImageViews) bound to the framebuffer. Each item of the list shows the info of the image view.

  4. Image node shows the info of the image bound to the image view.

Bound renderpass

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  1. Renderpass node shows the info of the renderpass currently used for rendering. It gets updated after each VkCmdBeginRenderPass executes on the same queue.

  2. AttachmentDescriptions node lists all the VkAttachmentDescription of the current renderpass in use.

  3. SubpassDescriptions node lists the VkSubpassDescription for each subpass.

  4. SubpassDependencies node lists the VkSubpassDependency for each subpass.

Bound descriptor sets

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  1. DescriptorSets node lists all the currently bound descriptor sets. The list of bounded descriptor sets reflect the state after the last vkCmdBindDescriptorSets being rolled out on the same queue, and the original descriptor set info will be overwritten or new info will be added according to the parameters of the last executed vkCmdBindDescriptorSets.

  2. Bindings node lists all the currently bound descriptor bindings in the descriptor set.

  3. Each descriptor binding also lists its bound descriptors.

  4. Layout node shows the info of the VkDescriptorSetLayout used to allocate the descriptor set.

Bound graphics pipeline

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  1. GraphicsPipeline node contains the info about the last bound graphics pipeline. This node gets updated after each VkCmdBindPipeline executes on the current queue.

Bound buffers

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  1. BoundVertexBuffers node lists all the bound vertex buffers. For each bound vertex buffer, it shows the info of the backing buffer. The list gets updated accordingly after each vkCmdBindVertexBuffers executes on the same queue.

  2. BoundIndexBuffer node shows the last bound index buffer, including the index type and the info of the backing buffer.

Draw command parameters

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  1. CommandParameters node contains the parameters to vkCmdDraw, vkCmdDrawIndexed, vkCmdDrawIndirect and vkCmdDrawIndirectIndexed. For each type of drawining command, there is a corresponding sub-node to contains the parameter values. As these four types of drawining commands cannot be used at the same time, only one of the four sub-nodes can be populated at a time. The content of CommandParameters gets updated after any one of the four drawining commands being executed on the same queue.