face_sdk/vulkan/framework/rendering/postprocessing_renderpass.h

/* Copyright (c) 2020-2025, Arm Limited and Contributors
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 the "License";
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include "core/sampled_image.h"
#include "postprocessing_pass.h"
#include "render_pipeline.h"
#include "subpass.h"

namespace vkb
{
/**
 * @brief An utility struct for hashing pairs.
 */
struct PairHasher
{
	template <typename TPair>
	size_t operator()(const TPair &pair) const
	{
		std::hash<decltype(pair.first)>  hash1{};
		std::hash<decltype(pair.second)> hash2{};
		return hash1(pair.first) * 43 + pair.second;
	}
};

/**
 * @brief Maps in-shader binding names to indices into a RenderTarget's attachments.
 */
using AttachmentMap = std::unordered_map<std::string, uint32_t>;

/**
 * @brief Maps in-shader binding names to the core::SampledImage to bind.
 */
using SampledMap = std::unordered_map<std::string, core::SampledImage>;

/**
 * @brief Maps in-shader binding names to the core::ImageView to bind for storage images.
 */
using StorageImageMap = std::unordered_map<std::string, const core::ImageView *>;

/**
 * @brief A list of indices into a RenderTarget's attachments.
 */
using AttachmentList = std::vector<uint32_t>;

/**
 * @brief A set of indices into a RenderTarget's attachments.
 */
using AttachmentSet = std::unordered_set<uint32_t>;

class PostProcessingRenderPass;

/**
 * @brief A single step of a vkb::PostProcessingRenderPass.
 */
class PostProcessingSubpass : public vkb::rendering::SubpassC
{
  public:
	PostProcessingSubpass(PostProcessingRenderPass *parent, RenderContext &render_context, ShaderSource &&triangle_vs,
	                      ShaderSource &&fs, ShaderVariant &&fs_variant = {});

	PostProcessingSubpass(const PostProcessingSubpass &to_copy)            = delete;
	PostProcessingSubpass &operator=(const PostProcessingSubpass &to_copy) = delete;

	PostProcessingSubpass(PostProcessingSubpass &&to_move);
	PostProcessingSubpass &operator=(PostProcessingSubpass &&to_move) = delete;

	~PostProcessingSubpass() = default;

	/**
	 * @brief Maps the names of input attachments in the shader to indices into the render target's images.
	 *        These are given as `subpassInput`s to the subpass, at set 0; they are bound automatically according to their name.
	 */
	inline const AttachmentMap &get_input_attachments() const
	{
		return input_attachments;
	}

	/**
	 * @brief Maps the names of samplers in the shader to vkb::core::SampledImage.
	 *        These are given as samplers to the subpass, at set 0; they are bound automatically according to their name.
	 * @remarks PostProcessingPipeline::get_sampler() is used as the default sampler if none is specified.
	 *          The RenderTarget for the current PostProcessingSubpass is used if none is specified for attachment images.
	 */
	inline const SampledMap &get_sampled_images() const
	{
		return sampled_images;
	}

	/**
	 * @brief Maps the names of storage images in the shader to vkb::core::ImageView.
	 *        These are given as image2D[Array] to the subpass, at set 0; they are bound automatically according to their name.
	 */
	inline const StorageImageMap &get_storage_images() const
	{
		return storage_images;
	}

	/**
	 * @brief Returns the shader variant used for this postprocess' fragment shader.
	 */
	inline ShaderVariant &get_fs_variant()
	{
		return fs_variant;
	}

	/**
	 * @brief Sets the shader variant that will be used for this postprocess' fragment shader.
	 */
	inline PostProcessingSubpass &set_fs_variant(ShaderVariant &&new_variant)
	{
		fs_variant = std::move(new_variant);

		return *this;
	}

	/**
	 * @brief Changes the debug name of this Subpass.
	 */
	inline PostProcessingSubpass &set_debug_name(const std::string &name)
	{
		Subpass::set_debug_name(name);

		return *this;
	}

	/**
	 * @brief Changes (or adds) the input attachment at name for this step.
	 */
	PostProcessingSubpass &bind_input_attachment(const std::string &name, uint32_t new_input_attachment);

	/**
	 * @brief Changes (or adds) the sampled image at name for this step.
	 * @remarks If no RenderTarget is specifically set for the core::SampledImage,
	 *          it will default to sample in the RenderTarget currently bound for drawing in the parent PostProcessingRenderpass.
	 */
	PostProcessingSubpass &bind_sampled_image(const std::string &name, core::SampledImage &&new_image);

	/**
	 * @brief Changes (or adds) the storage image at name for this step.
	 */
	PostProcessingSubpass &bind_storage_image(const std::string &name, const core::ImageView &new_image);

	/**
	 * @brief Removes the sampled image at name for this step.
	 */
	void unbind_sampled_image(const std::string &name);

	/**
	 * @brief Set the constants that are pushed before each fullscreen draw.
	 */
	PostProcessingSubpass &set_push_constants(const std::vector<uint8_t> &data);

	/**
	 * @brief Set the constants that are pushed before each fullscreen draw.
	 */
	template <typename T>
	inline PostProcessingSubpass &set_push_constants(const T &data)
	{
		push_constants_data.reserve(sizeof(data));
		auto data_ptr = reinterpret_cast<const uint8_t *>(&data);
		push_constants_data.assign(data_ptr, data_ptr + sizeof(data));

		return *this;
	}

	/**
	 * @brief A functor used to draw the primitives for a post-processing step.
	 * @see default_draw_func()
	 */
	using DrawFunc = std::function<void(vkb::core::CommandBufferC &command_buffer, RenderTarget &render_target)>;

	/**
	 * @brief Sets the function used to draw this postprocessing step.
	 * @see default_draw_func()
	 */
	PostProcessingSubpass &set_draw_func(DrawFunc &&new_func);

	/**
	 * @brief The default function used to draw a step; it draws 1 instance with 3 vertices.
	 */
	static void default_draw_func(vkb::core::CommandBufferC &command_buffer, vkb::RenderTarget &render_target);

  private:
	PostProcessingRenderPass *parent;

	ShaderVariant fs_variant{};

	AttachmentMap   input_attachments{};
	SampledMap      sampled_images{};
	StorageImageMap storage_images{};

	std::vector<uint8_t> push_constants_data{};

	DrawFunc draw_func{&PostProcessingSubpass::default_draw_func};

	void prepare() override;
	void draw(vkb::core::CommandBufferC &command_buffer) override;
};

/**
 * @brief A collection of vkb::PostProcessingSubpass that are run as a single renderpass.
 */
class PostProcessingRenderPass : public PostProcessingPass<PostProcessingRenderPass>
{
  public:
	friend class PostProcessingSubpass;

	PostProcessingRenderPass(PostProcessingPipeline *parent, std::unique_ptr<core::Sampler> &&default_sampler = nullptr);

	PostProcessingRenderPass(const PostProcessingRenderPass &to_copy)            = delete;
	PostProcessingRenderPass &operator=(const PostProcessingRenderPass &to_copy) = delete;

	PostProcessingRenderPass(PostProcessingRenderPass &&to_move)            = default;
	PostProcessingRenderPass &operator=(PostProcessingRenderPass &&to_move) = default;

	void draw(vkb::core::CommandBufferC &command_buffer, RenderTarget &default_render_target) override;

	/**
	 * @brief Gets the step at the given index.
	 */
	inline PostProcessingSubpass &get_subpass(size_t index)
	{
		assert(index < pipeline.get_subpasses().size());
		return *dynamic_cast<PostProcessingSubpass *>(pipeline.get_subpasses()[index].get());
	}

	/**
	 * @brief Constructs a new PostProcessingSubpass and adds it to the tail of the pipeline.
	 * @remarks `this`, the render context and the vertex shader source are passed automatically before `args`.
	 * @returns The inserted step.
	 */
	template <typename... ConstructorArgs>
	PostProcessingSubpass &add_subpass(ConstructorArgs &&...args)
	{
		ShaderSource vs_copy         = get_triangle_vs();
		auto         new_subpass     = std::make_unique<PostProcessingSubpass>(this, get_render_context(), std::move(vs_copy), std::forward<ConstructorArgs>(args)...);
		auto        &new_subpass_ref = *new_subpass;

		pipeline.add_subpass(std::move(new_subpass));

		return new_subpass_ref;
	}

	/**
	 * @brief Set the uniform data to be bound at set 0, binding 0.
	 */
	template <typename T>
	inline PostProcessingRenderPass &set_uniform_data(const T &data)
	{
		uniform_data.reserve(sizeof(data));
		auto data_ptr = reinterpret_cast<const uint8_t *>(&data);
		uniform_data.assign(data_ptr, data_ptr + sizeof(data));

		return *this;
	}

	/**
	 * @copydoc set_uniform_data(const T&)
	 */
	inline PostProcessingRenderPass &set_uniform_data(const std::vector<uint8_t> &data)
	{
		uniform_data = data;

		return *this;
	}

  private:
	// An attachment sampled from a rendertarget
	using SampledAttachmentSet = std::unordered_set<std::pair<RenderTarget *, uint32_t>, PairHasher>;

	/**
	 * @brief Transition input, sampled and output attachments as appropriate.
	 * @remarks If a RenderTarget is not explicitly set for this pass, fallback_render_target is used.
	 */
	void transition_attachments(const AttachmentSet        &input_attachments,
	                            const SampledAttachmentSet &sampled_attachments,
	                            const AttachmentSet        &output_attachments,
	                            vkb::core::CommandBufferC  &command_buffer,
	                            RenderTarget               &fallback_render_target);

	/**
	 * @brief Select appropriate load/store operations for each buffer of render_target,
	 *        according to the subpass inputs/sampled inputs/subpass outputs of all steps
	 *        in the pipeline.
	 * @remarks If a RenderTarget is not explicitly set for this pass, fallback_render_target is used.
	 */
	void update_load_stores(const AttachmentSet        &input_attachments,
	                        const SampledAttachmentSet &sampled_attachments,
	                        const AttachmentSet        &output_attachments,
	                        const RenderTarget         &fallback_render_target);

	/**
	 * @brief Transition images and prepare load/stores before draw()ing.
	 */
	void prepare_draw(vkb::core::CommandBufferC &command_buffer, RenderTarget &fallback_render_target);

	BarrierInfo get_src_barrier_info() const override;
	BarrierInfo get_dst_barrier_info() const override;

	RenderPipeline                     pipeline{};
	std::unique_ptr<core::Sampler>     default_sampler{};
	std::unique_ptr<core::Sampler>     default_sampler_nearest{};
	RenderTarget                      *draw_render_target{nullptr};
	std::vector<LoadStoreInfo>         load_stores{};
	bool                               load_stores_dirty{true};
	std::vector<uint8_t>               uniform_data{};
	std::shared_ptr<BufferAllocationC> uniform_buffer_alloc{};
};

}        // namespace vkb