PostprocManager.h

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/* Copyright (C) 2023 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef INCLUDED_POSTPROCMANAGER
#define INCLUDED_POSTPROCMANAGER

#include "graphics/ShaderTechniquePtr.h"
#include "ps/CStr.h"
#include "renderer/backend/IFramebuffer.h"
#include "renderer/backend/IDeviceCommandContext.h"
#include "renderer/backend/IShaderProgram.h"
#include "renderer/backend/ITexture.h"

#include <array>
#include <vector>

class CPostprocManager
{
public:
    CPostprocManager();
    ~CPostprocManager();

    // Returns true if the the manager can be used.
    bool IsEnabled() const;

    // Create all buffers/textures in GPU memory and set default effect.
    // @note Must be called before using in the renderer. May be called multiple times.
    void Initialize();

    // Update the size of the screen
    void Resize();

    // Returns a list of xml files found in shaders/effects/postproc.
    static std::vector<CStrW> GetPostEffects();

    // Returns the name of the current effect.
    const CStrW& GetPostEffect() const
    {
        return m_PostProcEffect;
    }

    // Sets the current effect.
    void SetPostEffect(const CStrW& name);

    // Triggers update of shaders and FBO if needed.
    void UpdateAntiAliasingTechnique();
    void UpdateSharpeningTechnique();
    void UpdateSharpnessFactor();

    void SetDepthBufferClipPlanes(float nearPlane, float farPlane);

    // @note CPostprocManager must be initialized first
    Renderer::Backend::IFramebuffer* PrepareAndGetOutputFramebuffer();

    // First renders blur textures, then calls ApplyEffect for each effect pass,
    // ping-ponging the buffers at each step.
    // @note CPostprocManager must be initialized first
    void ApplyPostproc(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    // Blits the final postprocessed texture to the system framebuffer. The system
    // framebuffer is selected as the output buffer. Should be called before
    // silhouette rendering.
    // @note CPostprocManager must be initialized first
    void BlitOutputFramebuffer(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        Renderer::Backend::IFramebuffer* destination);

    // Returns true if we render main scene in the MSAA framebuffer.
    bool IsMultisampleEnabled() const;

    // Resolves the MSAA framebuffer into the regular one.
    void ResolveMultisampleFramebuffer(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

private:
    void CreateMultisampleBuffer();
    void DestroyMultisampleBuffer();

    std::unique_ptr<Renderer::Backend::IFramebuffer> m_CaptureFramebuffer;

    // Two framebuffers, that we flip between at each shader pass.
    std::unique_ptr<Renderer::Backend::IFramebuffer>
        m_PingFramebuffer, m_PongFramebuffer;

    // Unique color textures for the framebuffers.
    std::unique_ptr<Renderer::Backend::ITexture> m_ColorTex1, m_ColorTex2;

    // The framebuffers share a depth/stencil texture.
    std::unique_ptr<Renderer::Backend::ITexture> m_DepthTex;
    float m_NearPlane, m_FarPlane;

    // A framebuffer and textures x2 for each blur level we render.
    struct BlurScale
    {
        struct Step
        {
            std::unique_ptr<Renderer::Backend::IFramebuffer> framebuffer;
            std::unique_ptr<Renderer::Backend::ITexture> texture;
        };
        std::array<Step, 2> steps;
    };
    std::array<BlurScale, 3> m_BlurScales;

    // Indicates which of the ping-pong buffers is used for reading and which for drawing.
    bool m_WhichBuffer;

    Renderer::Backend::IVertexInputLayout* m_VertexInputLayout = nullptr;

    // The name and shader technique we are using. "default" name means no technique is used
    // (i.e. while we do allocate the buffers, no effects are rendered).
    CStrW m_PostProcEffect;
    CShaderTechniquePtr m_PostProcTech;

    CStr m_SharpName;
    CShaderTechniquePtr m_SharpTech;
    float m_Sharpness;

    CStr m_AAName;
    CShaderTechniquePtr m_AATech;
    bool m_UsingMultisampleBuffer;
    std::unique_ptr<Renderer::Backend::IFramebuffer> m_MultisampleFramebuffer;
    std::unique_ptr<Renderer::Backend::ITexture>
        m_MultisampleColorTex, m_MultisampleDepthTex;
    uint32_t m_MultisampleCount;
    std::vector<uint32_t> m_AllowedSampleCounts;

    // The current screen dimensions in pixels.
    int m_Width, m_Height;

    // Is the postproc manager initialized? Buffers created? Default effect loaded?
    bool m_IsInitialized;

    // Creates blur textures at various scales, for bloom, DOF, etc.
    void ApplyBlur(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext);

    // High quality GPU image scaling to half size. outTex must have exactly half the size
    // of inTex. inWidth and inHeight are the dimensions of inTex in texels.
    void ApplyBlurDownscale2x(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        Renderer::Backend::IFramebuffer* framebuffer,
        Renderer::Backend::ITexture* inTex,
        int inWidth, int inHeight);

    // GPU-based Gaussian blur in two passes. inOutTex contains the input image and will be filled
    // with the blurred image. tempTex must have the same size as inOutTex.
    // inWidth and inHeight are the dimensions of the images in texels.
    void ApplyBlurGauss(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        Renderer::Backend::ITexture* inTex,
        Renderer::Backend::ITexture* tempTex,
        Renderer::Backend::IFramebuffer* tempFramebuffer,
        Renderer::Backend::IFramebuffer* outFramebuffer,
        int inWidth, int inHeight);

    // Applies a pass of a given effect to the entire current framebuffer. The shader is
    // provided with a number of general-purpose variables, including the rendered screen so far,
    // the depth buffer, a number of blur textures, the screen size, the zNear/zFar planes and
    // some other parameters used by the optional bloom/HDR pass.
    void ApplyEffect(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        const CShaderTechniquePtr& shaderTech, int pass);

    // Delete all allocated buffers/textures from GPU memory.
    void Cleanup();

    // Delete existing buffers/textures and create them again, using a new screen size if needed.
    // (the textures are also attached to the framebuffers)
    void RecreateBuffers();
};

#endif // INCLUDED_POSTPROCMANAGER