ShaderTechnique.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/>.
 */

#ifndef INCLUDED_SHADERTECHNIQUE
#define INCLUDED_SHADERTECHNIQUE

#include "graphics/ShaderProgramPtr.h"
#include "lib/ogl.h"

/**
 * Implements a render pass consisting of various GL state changes and a shader,
 * used by CShaderTechnique.
 */
class CShaderPass
{
public:
    CShaderPass();

    /**
     * Set the shader program used for rendering with this pass.
     */
    void SetShader(const CShaderProgramPtr& shader) { m_Shader = shader; }

    // Add various bits of GL state to the pass:
    void AlphaFunc(GLenum func, GLclampf ref);
    void BlendFunc(GLenum src, GLenum dst);
    void ColorMask(GLboolean r, GLboolean g, GLboolean b, GLboolean a);
    void DepthMask(GLboolean mask);
    void DepthFunc(GLenum func);

    /**
     * Set up all the GL state that was previously specified on this pass.
     */
    void Bind();

    /**
     * Reset the GL state to the default.
     */
    void Unbind();

    const CShaderProgramPtr& GetShader() const { return m_Shader; }

private:
    CShaderProgramPtr m_Shader;

    bool m_HasAlpha;
    GLenum m_AlphaFunc;
    GLclampf m_AlphaRef;

    bool m_HasBlend;
    GLenum m_BlendSrc;
    GLenum m_BlendDst;

    bool m_HasColorMask;
    GLboolean m_ColorMaskR;
    GLboolean m_ColorMaskG;
    GLboolean m_ColorMaskB;
    GLboolean m_ColorMaskA;

    bool m_HasDepthMask;
    GLboolean m_DepthMask;

    bool m_HasDepthFunc;
    GLenum m_DepthFunc;
};

/**
 * Implements a render technique consisting of a sequence of passes.
 * CShaderManager loads these from shader effect XML files.
 */
class CShaderTechnique
{
public:
    CShaderTechnique();
    void AddPass(const CShaderPass& pass);

    int GetNumPasses() const;

    void BeginPass(int pass = 0);
    void EndPass(int pass = 0);
    const CShaderProgramPtr& GetShader(int pass = 0) const;

    /**
     * Whether this technique uses alpha blending that requires objects to be
     * drawn from furthest to nearest.
     */
    bool GetSortByDistance() const;

    void SetSortByDistance(bool enable);

    void Reset();

private:
    std::vector<CShaderPass> m_Passes;

    bool m_SortByDistance;
};

typedef shared_ptr<CShaderTechnique> CShaderTechniquePtr;

#endif // INCLUDED_SHADERTECHNIQUE