TerrainRenderer.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/>.
 */

/*
 * Terrain rendering (everything related to patches and water) is
 * encapsulated in TerrainRenderer
 */

#ifndef INCLUDED_TERRAINRENDERER
#define INCLUDED_TERRAINRENDERER

#include "graphics/Color.h"
#include "maths/BoundingBoxAligned.h"
#include "renderer/backend/IDeviceCommandContext.h"
#include "renderer/backend/ITexture.h"
#include "renderer/backend/IShaderProgram.h"

class CCamera;
class CCanvas2D;
class CModelDecal;
class CPatch;
class CShaderDefines;
class CSimulation2;
class CVector2D;

class ShadowMap;

struct TerrainRendererInternals;

/**
 * Class TerrainRenderer: Render everything related to the terrain,
 * especially patches and water.
 */
class TerrainRenderer
{
    friend class CPatchRData;
    friend class CDecalRData;

public:
    TerrainRenderer();
    ~TerrainRenderer();

    void Initialize();

    /**
     * Set the simulation context for this frame.
     * Call at start of frame, before any other Submits.
     */
    void SetSimulation(CSimulation2* simulation);

    /**
     * Submit: Add a patch for rendering in this frame.
     *
     * preconditions  : PrepareForRendering must not have been called
     * for this frame yet.
     * The patch must not have been submitted in this frame yet (i.e. you
     * can only submit a frame once).
     *
     * @param patch the patch
     */
    void Submit(int cullGroup, CPatch* patch);

    /**
     * Submit: Add a terrain decal for rendering in this frame.
     */
    void Submit(int cullGroup, CModelDecal* decal);

    /**
     * PrepareForRendering: Prepare internal data structures like vertex
     * buffers for rendering.
     *
     * All patches must have been submitted before the call to
     * PrepareForRendering.
     * PrepareForRendering must be called before any rendering calls.
     */
    void PrepareForRendering();

    /**
     * EndFrame: Remove all patches from the list of submitted patches.
     */
    void EndFrame();

    /**
     * Render textured terrain (including blends between
     * different terrain types).
     *
     * preconditions  : PrepareForRendering must have been called this
     * frame before calling RenderTerrain.
     *
     * @param deviceCommandContext A context to submit commands.
     * @param shadow A prepared shadow map, in case rendering with shadows is enabled.
     */
    void RenderTerrainShader(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        const CShaderDefines& context, int cullGroup, ShadowMap* shadow);

    /**
     * RenderPatches: Render all patches un-textured as polygons.
     *
     * preconditions  : PrepareForRendering must have been called this
     * frame before calling RenderPatches.
     *
     * @param filtered If true then only render objects that passed CullPatches.
     * @param color Fill color of the patches.
     */
    void RenderPatches(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        int cullGroup, const CShaderDefines& defines,
        const CColor& color = CColor(0.0f, 0.0f, 0.0f, 1.0f));

    /**
     * RenderOutlines: Render the outline of patches as lines.
     *
     * preconditions  : PrepareForRendering must have been called this
     * frame before calling RenderOutlines.
     *
     * @param filtered If true then only render objects that passed CullPatches.
     */
    void RenderOutlines(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        int cullGroup);

    /**
     * RenderWater: Render water for all patches that have been submitted
     * this frame.
     *
     * preconditions  : PrepareForRendering must have been called this
     * frame before calling RenderWater.
     */
    void RenderWater(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        const CShaderDefines& context, int cullGroup, ShadowMap* shadow);

    /**
     * Renders terrain to a framebuffer to occlude shore foams.
     */
    void RenderWaterFoamOccluders(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        int cullGroup);

    /**
     * Calculate a scissor rectangle for the visible water patches.
     */
    CBoundingBoxAligned ScissorWater(int cullGroup, const CCamera& camera);

    /**
     * Render priority text for all submitted patches, for debugging.
     */
    void RenderPriorities(CCanvas2D& canvas, int cullGroup);

    /**
     * Render texture unit 0 over the terrain mesh, with UV coords calculated
     * by the given texture matrix.
     * Intended for use by TerrainTextureOverlay.
     */
    void RenderTerrainOverlayTexture(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        int cullGroup, const CVector2D& textureTransform, Renderer::Backend::ITexture* texture);

private:
    TerrainRendererInternals* m;

    /**
     * RenderFancyWater: internal rendering method for fancy water.
     * Returns false if unable to render with fancy water.
     */
    bool RenderFancyWater(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        const CShaderDefines& context, int cullGroup, ShadowMap* shadow);

    /**
     * RenderSimpleWater: internal rendering method for water
     */
    void RenderSimpleWater(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        int cullGroup);

    static void PrepareShader(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext,
        Renderer::Backend::IShaderProgram* shader, ShadowMap* shadow);
};

#endif // INCLUDED_TERRAINRENDERER