Method prepare_offscreen_buffer

samples/api/hdr/hdr.cpp:288–527

Prepare a new framebuffer and attachments for offscreen rendering (G-Buffer)

// Prepare a new framebuffer and attachments for offscreen rendering (G-Buffer)
void HDR::prepare_offscreen_buffer()
{
	// We need to select a format that supports the color attachment blending flag, so we iterate over multiple formats to find one that supports this flag
	const std::vector<VkFormat> float_format_priority_list = {
	    VK_FORMAT_R32G32B32A32_SFLOAT,
	    VK_FORMAT_R16G16B16A16_SFLOAT        // Guaranteed blend support for this
	};

	VkFormat color_format = vkb::choose_blendable_format(get_device().get_gpu().get_handle(), float_format_priority_list);

	{
		offscreen.width  = width;
		offscreen.height = height;

		// Color attachments

		// We are using two 128-Bit RGBA floating point color buffers for this sample
		// In a performance or bandwidth-limited scenario you should consider using a format with lower precision
		create_attachment(color_format, VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT, &offscreen.color[0]);
		create_attachment(color_format, VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT, &offscreen.color[1]);
		// Depth attachment
		create_attachment(depth_format, VK_IMAGE_USAGE_DEPTH_STENCIL_ATTACHMENT_BIT, &offscreen.depth);

		// Set up separate renderpass with references to the color and depth attachments
		std::array<VkAttachmentDescription, 3> attachment_descriptions = {};

		// Init attachment properties
		for (uint32_t i = 0; i < 3; ++i)
		{
			attachment_descriptions[i].samples        = VK_SAMPLE_COUNT_1_BIT;
			attachment_descriptions[i].loadOp         = VK_ATTACHMENT_LOAD_OP_CLEAR;
			attachment_descriptions[i].storeOp        = VK_ATTACHMENT_STORE_OP_STORE;
			attachment_descriptions[i].stencilLoadOp  = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
			attachment_descriptions[i].stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
			if (i == 2)
			{
				attachment_descriptions[i].initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
				attachment_descriptions[i].finalLayout   = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL;
			}
			else
			{
				attachment_descriptions[i].initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
				attachment_descriptions[i].finalLayout   = VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL;
			}
		}

		// Formats
		attachment_descriptions[0].format = offscreen.color[0].format;
		attachment_descriptions[1].format = offscreen.color[1].format;
		attachment_descriptions[2].format = offscreen.depth.format;

		std::vector<VkAttachmentReference> color_references;
		color_references.push_back({0, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL});
		color_references.push_back({1, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL});

		VkAttachmentReference depth_reference = {};
		depth_reference.attachment            = 2;
		depth_reference.layout                = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL;