Tutorial_504_Transparency/main.cpp

This example shows how to render a surface mesh with transparency effect using the following techniques

• Average Color Blending
• Dual Depth Peeling

The header file of the viewer class:

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D 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.
 *
 * Easy3D 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/>.
 ********************************************************************/
 
#ifndef EASY3D_TUTORIAL_TRANSPARENCY_H
#define EASY3D_TUTORIAL_TRANSPARENCY_H
 
#include <easy3d/viewer/viewer.h>
 
 
// This class renders a surface mesh with transparency effect using the 
// Average Color Blending technique.
 
namespace easy3d {
    class Transparency;
}
 
class TutorialTransparency : public easy3d::Viewer
{
public:
    explicit TutorialTransparency(const std::string& title = "");
    ~TutorialTransparency() override;
 
protected:
    bool key_press_event(int key, int modifiers) override;
    void draw() const override;
 
private:
    easy3d::Transparency* transparency_;
    int method_;    // 0: disabled; 1: ACB; 2: DDP
};
 
 
#endif // EASY3D_TUTORIAL_TRANSPARENCY_H

The source file of the viewer class:

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D 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.
 *
 * Easy3D 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/>.
 ********************************************************************/
 
#include "viewer.h"
#include <easy3d/core/model.h>
#include <easy3d/renderer/average_color_blending.h>
#include <easy3d/renderer/dual_depth_peeling.h>
#include <easy3d/renderer/drawable_triangles.h>
#include <easy3d/renderer/renderer.h>
#include <easy3d/renderer/camera.h>
 
 
using namespace easy3d;
 
// \cond
 
TutorialTransparency::TutorialTransparency(const std::string& title) : Viewer(title) {
    transparency_ = new DualDepthPeeling(camera());
    std::cout << "method: Dual Depth Peeling" << std::endl;
    method_ = 2;
 
    hint_ = "Press 'space' to switch between different transparency techniques\n"
            "Press 'up/down' to increase/decrease the transparency";
}
 
 
TutorialTransparency::~TutorialTransparency() {
    delete transparency_;
 
    // Not needed: it will be called in the destructor of the base class
    //Viewer::cleanup();
}
 
 
bool TutorialTransparency::key_press_event(int key, int modifiers) {
    if (key == KEY_SPACE) {
        if (transparency_) {
            delete transparency_;
            transparency_ = nullptr;
        }
 
        method_ = (method_ + 1) % 3;
        switch (method_)
        {
        case 0:
            std::cout << "method: NULL(transparency disabled)" << std::endl;
            break;
        case 1:
            transparency_ = new AverageColorBlending(camera());
            std::cout << "method: Average Color Blending" << std::endl;
            break;
        case 2:
            transparency_ = new DualDepthPeeling(camera());
            std::cout << "method: Dual Depth Peeling" << std::endl;
            break;
        }
        update();
        return true;
    }
    else if (key == KEY_DOWN) {
        auto faces = current_model()->renderer()->get_triangles_drawable("faces");
        if (faces) {
            float o = faces->opacity();
            if (o > 0)
                faces->set_opacity(o - 0.1f);
            // make sure it is valid
            if (faces->opacity() <= 0)
                faces->set_opacity(0.1f);
            std::cout << "opacity: " << faces->opacity() << std::endl;
            update();
        }
        return true;
    }
    else if (key == KEY_UP) {
        auto faces = current_model()->renderer()->get_triangles_drawable("faces");
        if (faces) {
            float o = faces->opacity();
            if (o > 0)
                faces->set_opacity(o + 0.1f);
            // make sure it is valid
            if (faces->opacity() >= 1.0f)
                faces->set_opacity(1.0f);
            std::cout << "opacity: " << faces->opacity() << std::endl;
            update();
        }
        return true;
    }
    else
        return Viewer::key_press_event(key, modifiers);
}
 
 
void TutorialTransparency::draw() const {
    if (!current_model()) {
        return;
    }
 
    std::vector<TrianglesDrawable*> surfaces;
    for (auto m : models_) {
        for (auto d : m->renderer()->triangles_drawables()) {
            if (d->type() == Drawable::DT_TRIANGLES)
                    surfaces.push_back(dynamic_cast<TrianglesDrawable*>(d.get()));
        }
    }
 
    if (method_ != 0)
        transparency_->draw(surfaces);
    else
        Viewer::draw();
}
 
// \endcond

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D 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.
 *
 * Easy3D 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/>.
 ********************************************************************/
 
#include "viewer.h"
#include <easy3d/core/surface_mesh.h>
#include <easy3d/renderer/drawable_triangles.h>
#include <easy3d/renderer/renderer.h>
#include <easy3d/util/resource.h>
#include <easy3d/util/initializer.h>
 
using namespace easy3d;
 
 
int main(int argc, char **argv) {
    // initialize Easy3D.
    initialize();
    const std::string file_name = resource::directory() + "/data/torusknot.obj";
 
    // create the viewer.
    TutorialTransparency viewer(EXAMPLE_TITLE);
 
    // Load a mesh model and create a drawable for the faces.
    if (!viewer.add_model(file_name, true)) {
        LOG(ERROR) << "failed to load model. Please make sure the file exists and format is correct.";
        return EXIT_FAILURE;
    }
 
    auto drawable = viewer.current_model()->renderer()->get_triangles_drawable("faces");
    drawable->set_smooth_shading(true);
    drawable->set_distinct_back_color(false);
 
    // run the viewer
    return viewer.run();
}