OpenSceneGraph/src/osgFX/Outline.cpp

// -*-c++-*-

/*
 * OpenSceneGraph - Copyright (C) 1998-2009 Robert Osfield
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * This library 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
 * OpenSceneGraph Public License for more details.
 */

/*
 * osgFX::Outline - Copyright (C) 2004,2009 Ulrich Hertlein
 */

#include <osgFX/Outline>
#include <osgFX/Registry>

#include <osg/Group>
#include <osg/Stencil>
#include <osg/CullFace>
#include <osg/PolygonMode>
#include <osg/LineWidth>
#include <osg/Material>
#include <osg/Texture1D>


namespace {
    const unsigned int Override_On = osg::StateAttribute::ON|osg::StateAttribute::OVERRIDE;
    const unsigned int Override_Off = osg::StateAttribute::OFF|osg::StateAttribute::OVERRIDE;
}


namespace osgFX
{
    /// Register prototype.
    Registry::Proxy proxy(new Outline);

    /**
     * Outline technique.
     */
    class Outline::OutlineTechnique : public Technique
    {
    public:
        /// Constructor.
        OutlineTechnique() : Technique(),
            _lineWidth(), _width(2),
            _material(), _color(1,1,1,1) {
        }

        /// Validate.
        bool validate(osg::State&) const {
            return true;
        }

        /// Set outline width.
        void setWidth(float w) {
            _width = w;
            if (_lineWidth.valid()) {
                _lineWidth->setWidth(w);
            }
        }

        /// Set outline color.
        void setColor(const osg::Vec4& color) {
            _color = color;
            if (_material.valid()) {
                const osg::Material::Face face = osg::Material::FRONT_AND_BACK;
                _material->setAmbient(face, color);
                _material->setDiffuse(face, color);
                _material->setEmission(face, color);
            }
        }

    protected:
        /// Define render passes.
        void define_passes() {

            /*
             * draw
             * - set stencil buffer to ref=1 where draw occurs
             * - clear stencil buffer to 0 where test fails
             */
            {
                osg::StateSet* state = new osg::StateSet;

                // stencil op
                osg::Stencil* stencil  = new osg::Stencil;
                stencil->setFunction(osg::Stencil::ALWAYS, 1, ~0u);
                stencil->setOperation(osg::Stencil::KEEP,
                                      osg::Stencil::KEEP,
                                      osg::Stencil::REPLACE);
                state->setAttributeAndModes(stencil, Override_On);

                addPass(state);
            }

            /*
             * post-draw
             * - only draw where draw didn't set the stencil buffer
             * - draw only back-facing polygons
             * - draw back-facing polys as lines
             * - disable depth-test, lighting & texture
             */
            {
                osg::StateSet* state = new osg::StateSet;

                // stencil op
                osg::Stencil* stencil  = new osg::Stencil;
                stencil->setFunction(osg::Stencil::NOTEQUAL, 1, ~0u);
                stencil->setOperation(osg::Stencil::KEEP,
                                      osg::Stencil::KEEP,
                                      osg::Stencil::REPLACE);
                state->setAttributeAndModes(stencil, Override_On);

                // cull front-facing polys
                osg::CullFace* cf = new osg::CullFace;
                cf->setMode(osg::CullFace::FRONT);
                state->setAttributeAndModes(cf, Override_On);

                // draw back-facing polygon lines
                osg::PolygonMode* pm = new osg::PolygonMode;
                pm->setMode(osg::PolygonMode::BACK, osg::PolygonMode::LINE);
                state->setAttributeAndModes(pm, Override_On);

                // outline width
                _lineWidth = new osg::LineWidth;
                setWidth(_width);
                state->setAttributeAndModes(_lineWidth, Override_On);

                // outline color/material
                _material = new osg::Material;
                _material->setColorMode(osg::Material::AMBIENT_AND_DIFFUSE);
                setColor(_color);
                state->setAttributeAndModes(_material, Override_On);

                // disable modes
                state->setMode(GL_BLEND, Override_Off);
                state->setMode(GL_DEPTH_TEST, Override_Off);
                state->setTextureMode(0, GL_TEXTURE_1D, Override_Off);
                state->setTextureMode(0, GL_TEXTURE_2D, Override_Off);
                state->setTextureMode(0, GL_TEXTURE_3D, Override_Off);

                addPass(state);
            }
        }

    private:
        /// Outline width.
        osg::ref_ptr<osg::LineWidth> _lineWidth;
        float _width;

        /// Outline Material.
        osg::ref_ptr<osg::Material> _material;
        osg::Vec4 _color;
    };


    /**
     * Outline effect.
     */
    Outline::Outline() : Effect(), _width(2), _color(1,1,1,1), _technique(0)
    {
    }

    void Outline::setWidth(float w)
    {
        _width = w;
        if (_technique) {
            _technique->setWidth(w);
        }
    }

    void Outline::setColor(const osg::Vec4& color)
    {
        _color = color;
        if (_technique) {
            _technique->setColor(color);
        }
    }

    bool Outline::define_techniques()
    {
        _technique = new OutlineTechnique;
        addTechnique(_technique);

        setWidth(_width);
        setColor(_color);

        return true;
    }
}