Tutorial_406_CollisionDetection/main.cpp

This example shows how to detect the intersecting faces using collision detection.

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_COLLISION_DETECTION_H
#define EASY3D_TUTORIAL_COLLISION_DETECTION_H
 
#include <easy3d/viewer/viewer.h>
#include <easy3d/util/timer.h>
 
// This class demonstrates how to detect intersecting faces of two meshes.
 
namespace easy3d {
    class Model;
    class Collider;
}
 
class TutorialCollisionDetection : public easy3d::Viewer {
public:
    explicit TutorialCollisionDetection(const std::string &title);
    ~TutorialCollisionDetection() override;
 
private:
    bool mouse_drag_event(int x, int y, int dx, int dy, int button, int modifiers) override;
    bool key_press_event(int key, int modifiers) override;
 
    void detect();
 
private:
    easy3d::Collider* collider_;
 
    easy3d::vec3 model0_color_;
    easy3d::vec3 model1_color_;
 
    easy3d::Timer<> timer_;
};
 
 
#endif // EASY3D_TUTORIAL_COLLISION_DETECTION_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 <mutex>
 
#include <easy3d/renderer/drawable_triangles.h>
#include <easy3d/renderer/manipulator.h>
#include <easy3d/renderer/manipulated_frame.h>
#include <easy3d/renderer/renderer.h>
#include <easy3d/util/resource.h>
#include <easy3d/algo/collider.h>
 
 
using namespace easy3d;
 
// \cond
 
TutorialCollisionDetection::TutorialCollisionDetection(const std::string &title)
        : Viewer(title)
        , model0_color_(0.8f, 1.0f, 0.8f)
        , model1_color_(0.8f, 0.8f, 1.0f)
{
    auto m0 = add_model(resource::directory() + "/data/bunny.ply");
    auto m1 = add_model(resource::directory() + "/data/mannequin.ply");
    auto mesh0 = dynamic_cast<SurfaceMesh*>(m0);
    auto mesh1 = dynamic_cast<SurfaceMesh*>(m1);
    if (mesh0 && mesh1) {
        // use the manipulator to transform the first model (visualization only and geometry is not changed)
        mesh0->set_manipulator(std::make_shared<Manipulator>(mesh0));
 
        // the first mesh is colored by a "face_color" property
        mesh0->add_face_property<vec3>("face_color", model0_color_);
        mesh0->renderer()->get_triangles_drawable("faces")->set_coloring(easy3d::State::COLOR_PROPERTY, easy3d::State::FACE, "face_color");
 
        // the second mesh is also colored by a "face_color" property
        mesh1->add_face_property<vec3>("face_color", model1_color_);
        mesh1->renderer()->get_triangles_drawable("faces")->set_coloring(easy3d::State::COLOR_PROPERTY, easy3d::State::FACE, "face_color");
 
        collider_ = new Collider(mesh0, mesh1);
        // detect and show the result when the viewer is visible
        detect();
 
        timer_.set_interval(50, [this]()->void {
            static std::mutex mutex; // ensures the previous changes are completed
            std::lock_guard<std::mutex> guard(mutex);
            static float angle = 0.0f;
            angle += 0.0001f;
            auto T = mat4::rotation(vec3(0, 0, 1), angle) * models_[0]->manipulator()->frame()->matrix();
            models_[0]->manipulator()->frame()->setFromMatrix(T);
            detect();
        });
    }
    else
        LOG(WARNING) << "not all the two meshes have been loaded";
 
    manual_ =
            "--------------------- Collision Viewer usage ----------------------\n"
            "On start, you will see an animation with highlighted intersecting  \n"
            "faces. Press 'space' to pause/resume the animation.                \n"
            "When the animation is paused, you can manipulate the bunny model   \n"
            "(using your mouse) to perform real-time collection detection:      \n"
            "    - Alt + left button: rotate bunny model                        \n"
            "    - Alt + right button: translate bunny model                    \n"
            "------------------------------------------------------------------ \n";
 
    hint_ = "Press 'space' to pause/resume animation\n"
            "When paused:\n"
            "  - Alt + left button: rotate bunny model\n"
            "  - Alt + right button: translate bunny model";
}
 
 
TutorialCollisionDetection::~TutorialCollisionDetection() {
    timer_.stop();
    delete collider_;
}
 
 
bool TutorialCollisionDetection::mouse_drag_event(int x, int y, int dx, int dy, int button, int modifiers) {
    if (collider_ && models().size() == 2 && modifiers == MODIF_ALT && timer_.is_paused()) {
        auto manipulator = models_[0]->manipulator();
        if (button == BUTTON_LEFT)
            manipulator->frame()->action_rotate(x, y, dx, dy, camera(), ManipulatedFrame::NONE);
        else if (button == BUTTON_RIGHT)
            manipulator->frame()->action_translate(x, y, dx, dy, camera(), ManipulatedFrame::NONE);
        else
            return false;
 
        detect();
        return true;
    }
    else
        return Viewer::mouse_drag_event(x, y, dx, dy, button, modifiers);
}
 
 
bool TutorialCollisionDetection::key_press_event(int key, int modifiers) {
    if (key == KEY_SPACE) {
        if (timer_.is_paused())
            timer_.resume();
        else
            timer_.pause();
        return true;
    }
    else
        return Viewer::key_press_event(key, modifiers);
}
 
 
void TutorialCollisionDetection::detect() {
    const auto pairs = collider_->detect(models_[0]->manipulator()->matrix(), mat4::identity());
    //std::cout << pairs.size() << " pairs of intersecting faces" << std::endl;
 
    // mark the intersecting faces red
    // Note: The following code is for visualizing the intersecting faces and is not optimized.
    //      Ideas for better performance:
    //          (1) update only the color buffer;
    //          (2) use a shader storage buffer to transfer the *status* of the faces to the fragment shader.
    auto mesh0 = dynamic_cast<SurfaceMesh *>(models_[0].get());
    auto mesh1 = dynamic_cast<SurfaceMesh *>(models_[1].get());
    auto mesh0_colors = mesh0->get_face_property<vec3>("face_color");
    auto mesh1_colors = mesh1->get_face_property<vec3>("face_color");
    mesh0_colors.vector().assign(mesh0->n_faces(), model0_color_);
    mesh1_colors.vector().assign(mesh1->n_faces(), model1_color_);
    for (const auto &pair : pairs) {
        mesh0_colors[pair.first] = vec3(1.0f, 0.0f, 0.0f);
        mesh1_colors[pair.second] = vec3(1.0f, 0.0f, 0.0f);
    }
    models_[0]->renderer()->update();
    models_[1]->renderer()->update();
 
    update();
}
 
// \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/util/initializer.h>
 
using namespace easy3d;
 
 
int main(int argc, char **argv) {
    // initialize Easy3D.
    initialize();
 
    TutorialCollisionDetection viewer(EXAMPLE_TITLE);
 
    // run the viewer
    return viewer.run();
}