RenderModifiers.h

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/* Copyright (C) 2012 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/>.
 */

/*
 * RenderModifiers can affect the fragment stage behaviour of some
 * ModelRenderers. This file defines some common RenderModifiers in
 * addition to the base class.
 * 
 * TODO: See comment in CRendererInternals::Models - we no longer use multiple
 * subclasses of RenderModifier, so most of the stuff here is unnecessary
 * abstraction which should probably be cleaned up.
 */

#ifndef INCLUDED_RENDERMODIFIERS
#define INCLUDED_RENDERMODIFIERS

#include "ModelRenderer.h"
#include "graphics/ShaderTechnique.h"
#include "graphics/Texture.h"

class CLightEnv;
class CMatrix3D;
class CModel;
class ShadowMap;

/**
 * Class RenderModifier: Some ModelRenderer implementations provide vertex
 * management behaviour but allow fragment stages to be modified by a plugged in
 * RenderModifier.
 *
 * You should use RenderModifierPtr when referencing RenderModifiers.
 */
class RenderModifier
{
public:
    RenderModifier() { }
    virtual ~RenderModifier() { }

    /**
     * BeginPass: Setup OpenGL for the given rendering pass.
     *
     * Must be implemented by derived classes.
     *
     * @param pass The current pass number (pass == 0 is the first pass)
     *
     * @return The streamflags that indicate which vertex components
     * are required by the fragment stages (see STREAM_XYZ constants).
     */
    virtual void BeginPass(const CShaderProgramPtr& shader) = 0;

    /**
     * PrepareModel: Called before rendering the given model.
     *
     * Default behaviour does nothing.
     *
     * @param pass The current pass number (pass == 0 is the first pass)
     * @param model The model that is about to be rendered.
     */
    virtual void PrepareModel(const CShaderProgramPtr& shader, CModel* model) = 0;
};


/**
 * Class LitRenderModifier: Abstract base class for RenderModifiers that apply
 * a shadow map.
 * LitRenderModifiers expect the diffuse brightness in the primary color (instead of ambient + diffuse).
 */
class LitRenderModifier : public RenderModifier
{
public:
    LitRenderModifier();
    ~LitRenderModifier();

    /**
     * SetShadowMap: Set the shadow map that will be used for rendering.
     * Must be called by the user of the RenderModifier.
     *
     * The shadow map must be non-null and use depth texturing, or subsequent rendering
     * using this RenderModifier will fail.
     *
     * @param shadow the shadow map
     */
    void SetShadowMap(const ShadowMap* shadow);

    /**
     * SetLightEnv: Set the light environment that will be used for rendering.
     * Must be called by the user of the RenderModifier.
     *
     * @param lightenv the light environment (must be non-null)
     */
    void SetLightEnv(const CLightEnv* lightenv);

    const ShadowMap* GetShadowMap() const { return m_Shadow; }
    const CLightEnv* GetLightEnv() const { return m_LightEnv; }

private:
    const ShadowMap* m_Shadow;
    const CLightEnv* m_LightEnv;
};

/**
 * A RenderModifier that sets uniforms and textures appropriately for rendering models.
 */
class ShaderRenderModifier : public LitRenderModifier
{
public:
    ShaderRenderModifier();

    // Implementation
    void BeginPass(const CShaderProgramPtr& shader);
    void PrepareModel(const CShaderProgramPtr& shader, CModel* model);

private:
    CShaderProgram::Binding m_BindingInstancingTransform;
    CShaderProgram::Binding m_BindingShadingColor;
    CShaderProgram::Binding m_BindingPlayerColor;
};

#endif // INCLUDED_RENDERMODIFIERS