shader.h

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/*
    This file is part of Mitsuba, a physically based rendering system.

    Copyright (c) 2007-2014 by Wenzel Jakob and others.

    Mitsuba is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License Version 3
    as published by the Free Software Foundation.

    Mitsuba 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/

#pragma once
#if !defined(__MITSUBA_RENDER_SHADER_H_)
#define __MITSUBA_RENDER_SHADER_H_

#include <mitsuba/mitsuba.h>

MTS_NAMESPACE_BEGIN

class Shader;
class Renderer;
class GPUProgram;

/**
 * \brief Abstract hardware resource.
 *
 * Implementations provides support for functionality that are also able to
 * live on the GPU. By default, the method 'createShader' just returns \c NULL,
 * which means that the BSDF/Light source/Texture/.. has not yet been ported
 * to the GPU-based renderer.
 */
class MTS_EXPORT_RENDER HWResource {
public:
        virtual Shader *createShader(Renderer *renderer) const;

        virtual ~HWResource() { }
};

/**
 * \brief %Shader base class for use with a VPL-style renderer.
 *
 * Subclasses can implement one of various things, such as a BSDF,
 * a light source, or a texture.
 *
 * \ingroup librender
 */
class MTS_EXPORT_RENDER Shader : public Object {
public:
        enum EShaderType {
                EBSDFShader = 0,
                ETextureShader,
                EEmitterShader
        };

        enum EFlags {
                ETransparent = 0x01
        };

        // Return the type of shader represented by this instance
        inline EShaderType getType() const { return m_type; }

        /// Return a list of flags
        inline uint32_t getFlags() const { return m_flags; }

        /**
         * \brief For transparent objects, this function returns
         * the alpha blending weight
         */
        virtual Float getAlpha() const;

        // List other shaders, on which this instance depends
        virtual void putDependencies(std::vector<Shader *> &deps);

        /**
         * \brief Is this shader complete?
         *
         * This is mainly useful to check whether all dependencies
         * could be constructed successfully. The default
         * implementation returns \c true.
         */
        virtual bool isComplete() const;

        /**
         * \brief Generate a string version of this shader's evaluation
         * routine.
         *
         * The appended string should assign the name \c evalName to this
         * function. The function names of depedencies (as specified by
         * \ref putDependencies), are supplied in the parameter \c depNames
         * in identical order.
         */
        virtual void generateCode(std::ostringstream &oss,
                        const std::string &evalName,
                        const std::vector<std::string> &depNames) const = 0;

        /**
         * \brief This function can optionally be implemented to resolve named
         * program parameters to numerical IDs for increased performance.
         *
         * The int array returned here will later be passed to \ref bind().
         * The default implementation does nothing.
         */
        virtual void resolve(const GPUProgram *program, const std::string &evalName,
                std::vector<int> &parameterIDs) const;

        /**
         * \brief Configure the the associated GPU program.
         *
         * This function is typically used to bind textures and
         * to set program pararameters.
         */
        virtual void bind(GPUProgram *program, const std::vector<int> &parameterIDs,
                int &textureUnitOffset) const;

        /// Release any bound resources.
        virtual void unbind() const;

        /// Release all resources
        virtual void cleanup(Renderer *renderer);

        MTS_DECLARE_CLASS()
protected:
        Shader(Renderer *renderer, EShaderType type);

        /// Virtual destructor
        virtual ~Shader();
protected:
        EShaderType m_type;
        uint32_t m_flags;
};

MTS_NAMESPACE_END

#endif /* __MITSUBA_RENDER_SHADER_H_ */