Tutorial_301_Drawables/main.cpp

Drawables are typically for rendering 3D models (e.g., point clouds, meshes, graphs) that are loaded from files or generated by some algorithms. The use of drawables for visualization is quite flexible. Drawables are normally attached to a 3D model. For example, you can attach a TrianglesDrawable to a surface mesh to visualize its surface and a PointsDrawable to visualize its vertices. Easy3D also allows visualizing stand-alone drawables (without creating a model).

This example shows how to

• visualize 3D data without explicitly defining a model (i.e., rendering drawables directly);
  • a set of points with PointsDrawable.
  • a set of triangles or a surface using TrianglesDrawable.
  • a set of edges/lines using LinesDrawable.
  • a set of edges/lines in screen coordinates using LinesDrawable2D.
• create a drawable for a specific rendering purpose;
• use the viewer to visualize drawables.

/********************************************************************
 * 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 <easy3d/viewer/viewer.h>
#include <easy3d/renderer/drawable_lines.h>
#include <easy3d/renderer/drawable_points.h>
#include <easy3d/renderer/drawable_triangles.h>
#include <easy3d/core/types.h>
#include <easy3d/util/resource.h>
#include <easy3d/util/initializer.h>
 
using namespace easy3d;
 
 
#if 1  // use the built-in drawables of Easy3D.
 
int main(int argc, char **argv) {
    // initialize Easy3D.
    initialize();
 
    //-------------------------------------------------------------
 
    // Create the default Easy3D viewer.
    // Note: a viewer must be created before creating any drawables.
    Viewer viewer(EXAMPLE_TITLE);
    viewer.set_usage("");
 
    //-------------------------------------------------------------
 
    // We visualize the "bunny".
 
    // The coordinates of the vertices.
    const std::vector<vec3> &points = resource::bunny_vertices;
    // The indices represent how the vertices are connected to form triangles. The "bunny" is a triangle mesh, and thus
    // each consecutive three indices represent a triangle.
    const std::vector<unsigned int> &indices = resource::bunny_indices;
 
    //-------------------------------------------------------------
    // Create a TrianglesDrawable to visualize the surface of the "bunny".
    // For visualization, the point positions and the vertex indices of the faces have to be sent to the GPU.
    auto surface = new TrianglesDrawable("faces");
    // Upload the vertex positions of the surface to the GPU.
    surface->update_vertex_buffer(points);
    // Upload the vertex indices of the surface to the GPU.
    surface->update_element_buffer(indices);
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<TrianglesDrawable>(surface));
 
    //-------------------------------------------------------------
    // Create a PointsDrawable to visualize the vertices of the "bunny".
    // Only the vertex positions have to be sent to the GPU for visualization.
    auto vertices = new PointsDrawable("vertices");
    // Upload the vertex positions to the GPU.
    vertices->update_vertex_buffer(points);
    // Set a color for the vertices (here we want a red color).
    vertices->set_uniform_coloring(vec4(1.0f, 0.0f, 0.0f, 1.0f));  // RBGA
    // Three options are available for visualizing points:
    //      - PLAIN: plain points (i.e., each point is a square on the screen);
    //      - SPHERE: each point is visualized a sphere;
    //      - SURFEL: each point is visualized an oriented disk.
    // In this example, let's render the vertices as spheres.
    vertices->set_impostor_type(PointsDrawable::SPHERE);
    // Set the vertices size (here 10 pixels).
    vertices->set_point_size(10);
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<PointsDrawable>(vertices));
 
    //-------------------------------------------------------------
    // Create a LinesDrawable to visualize the bounding box of the "bunny".
 
    // Compute the bounding box.
    auto bbox_drawable = new LinesDrawable("bbox");
    const Box3 &box = geom::bounding_box<Box3, std::vector<vec3> >(points);
    float xmin = box.min_coord(0);
    float xmax = box.max_coord(0);
    float ymin = box.min_coord(1);
    float ymax = box.max_coord(1);
    float zmin = box.min_coord(2);
    float zmax = box.max_coord(2);
    // The eight vertices of the bounding box.
    const std::vector<vec3> bbox_points = {
            vec3(xmin, ymin, zmax), vec3(xmax, ymin, zmax),
            vec3(xmin, ymax, zmax), vec3(xmax, ymax, zmax),
            vec3(xmin, ymin, zmin), vec3(xmax, ymin, zmin),
            vec3(xmin, ymax, zmin), vec3(xmax, ymax, zmin)
    };
    // The vertex indices of the twelve edges of the bounding box (each consecutive two numbers represent an edge).
    const std::vector<unsigned int> bbox_indices = {
            0, 1, 2, 3, 4, 5, 6, 7,
            0, 2, 4, 6, 1, 3, 5, 7,
            0, 4, 2, 6, 1, 5, 3, 7
    };
    // Upload the vertex positions of the bounding box to the GPU.
    bbox_drawable->update_vertex_buffer(bbox_points);
    // Upload the vertex indices of the bounding box to the GPU.
    bbox_drawable->update_element_buffer(bbox_indices);
    // Set a color for the edges of the bounding box (here we want a blue color).
    bbox_drawable->set_uniform_coloring(vec4(0.0f, 0.0f, 1.0f, 1.0f));    // r, g, b, a
    // Set the width of the edges (here 5 pixels).
    bbox_drawable->set_line_width(5.0f);
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<LinesDrawable>(bbox_drawable));
 
    //-------------------------------------------------------------
 
    // Make sure everything is within the visible region of the viewer.
    viewer.fit_screen();
 
    // run the viewer
    return viewer.run();
}
 
#elif 0 //  use the built-in drawables of Easy3D, but we provide customized update functions
 
int main(int argc, char **argv) {
    // initialize Easy3D.
    initialize();
 
    //-------------------------------------------------------------
 
    // Create the default Easy3D viewer.
    // Note: a viewer must be created before creating any drawables.
    Viewer viewer(EXAMPLE_TITLE);
    viewer.set_usage("");
 
    //-------------------------------------------------------------
 
    // We visualize the "bunny".
 
    // The coordinates of the vertices.
    const std::vector<vec3> &points = resource::bunny_vertices;
    // The indices represent how the vertices are connected to form triangles. The "bunny" is a triangle mesh, and thus
    // each consecutive three indices represent a triangle.
    const std::vector<unsigned int> &indices = resource::bunny_indices;
 
    //-------------------------------------------------------------
    // Create a TrianglesDrawable to visualize the surface of the "bunny".
    // For visualization, the point positions and the vertex indices of the faces have to be sent to the GPU.
    auto surface = new TrianglesDrawable("faces");
    surface->set_update_func([&points, &indices](Model* m, Drawable* d) {
        // Upload the vertex positions of the surface to the GPU.
        d->update_vertex_buffer(points);
        // Upload the vertex indices of the surface to the GPU.
        d->update_element_buffer(indices);
    });
 
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<TrianglesDrawable>(surface));
 
    //-------------------------------------------------------------
    // Create a PointsDrawable to visualize the vertices of the "bunny".
    // Only the vertex positions have to be sent to the GPU for visualization.
    auto vertices = new PointsDrawable("vertices");
    vertices->set_update_func([&points](Model* m, Drawable* d) {
        // Upload the vertex positions to the GPU.
        d->update_vertex_buffer(points);
    });
 
    // Set a color for the vertices (here we want a red color).
    vertices->set_uniform_coloring(vec4(1.0f, 0.0f, 0.0f, 1.0f));  // r, g, b, a
    // Three options are available for visualizing points:
    //      - PLAIN: plain points (i.e., each point is a square on the screen);
    //      - SPHERE: each point is visualized a sphere;
    //      - SURFEL: each point is visualized an oriented disk.
    // In this example, let's render the vertices as spheres.
    vertices->set_impostor_type(PointsDrawable::SPHERE);
    // Set the vertices size (here 10 pixels).
    vertices->set_point_size(10);
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<PointsDrawable>(vertices));
 
    //-------------------------------------------------------------
    // Create a LinesDrawable to visualize the bounding box of the "bunny".
 
    // Compute the bounding box.
    auto bbox_drawable = new LinesDrawable("bbox");
    bbox_drawable->set_update_func([&points](Model* m, Drawable* d) {
        const Box3 &box = geom::bounding_box<Box3, std::vector<vec3> >(points);
        float xmin = box.min_coord(0);
        float xmax = box.max_coord(0);
        float ymin = box.min_coord(1);
        float ymax = box.max_coord(1);
        float zmin = box.min_coord(2);
        float zmax = box.max_coord(2);
        // The eight vertices of the bounding box.
        const std::vector<vec3> bbox_points = {
                vec3(xmin, ymin, zmax), vec3(xmax, ymin, zmax),
                vec3(xmin, ymax, zmax), vec3(xmax, ymax, zmax),
                vec3(xmin, ymin, zmin), vec3(xmax, ymin, zmin),
                vec3(xmin, ymax, zmin), vec3(xmax, ymax, zmin)
        };
        // The vertex indices of the twelve edges of the bounding box (each consecutive two numbers represent an edge).
        const std::vector<unsigned int> bbox_indices = {
                0, 1, 2, 3, 4, 5, 6, 7,
                0, 2, 4, 6, 1, 3, 5, 7,
                0, 4, 2, 6, 1, 5, 3, 7
        };
 
        // Upload the vertex positions of the bounding box to the GPU.
        d->update_vertex_buffer(bbox_points);
        // Upload the vertex indices of the bounding box to the GPU.
        d->update_element_buffer(bbox_indices);
    });
 
    // Set a color for the edges of the bounding box (here we want a blue color).
    bbox_drawable->set_uniform_coloring(vec4(0.0f, 0.0f, 1.0f, 1.0f));    // r, g, b, a
    // Set the width of the edges (here 5 pixels).
    bbox_drawable->set_line_width(5.0f);
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<LinesDrawable>(bbox_drawable));
 
    //-------------------------------------------------------------
 
    // Make sure everything is within the visible region of the viewer.
    viewer.fit_screen();
 
    // run the viewer
    return viewer.run();
}
 
#else  // inherit customized drawables from Easy3D drawables, and we reimplement "void update_buffers_internal()"
 
class MyTrianglesDrawable : public TrianglesDrawable {
public:
    MyTrianglesDrawable(const std::string& name = "") : TrianglesDrawable(name) {}
 
protected:
    void update_buffers_internal() {
        // The coordinates of the vertices.
        const std::vector<vec3> &points = resource::bunny_vertices;
        // The indices represent how the vertices are connected to form triangles. The "bunny" is a triangle mesh, and thus
        // each consecutive three indices represent a triangle.
        const std::vector<unsigned int> &indices = resource::bunny_indices;
 
        // Upload the vertex positions of the surface to the GPU.
        update_vertex_buffer(points);
        // Upload the vertex indices of the surface to the GPU.
        update_element_buffer(indices);
    }
};
 
 
class MyLinesDrawable : public LinesDrawable {
public:
    MyLinesDrawable(const std::string& name = "") : LinesDrawable(name) {}
 
protected:
    void update_buffers_internal() {
        // The coordinates of the vertices.
        const std::vector<vec3> &points = resource::bunny_vertices;
        const Box3 &box = geom::bounding_box<Box3, std::vector<vec3> >(points);
        float xmin = box.min_coord(0);
        float xmax = box.max_coord(0);
        float ymin = box.min_coord(1);
        float ymax = box.max_coord(1);
        float zmin = box.min_coord(2);
        float zmax = box.max_coord(2);
        // The eight vertices of the bounding box.
        const std::vector<vec3> bbox_points = {
                vec3(xmin, ymin, zmax), vec3(xmax, ymin, zmax),
                vec3(xmin, ymax, zmax), vec3(xmax, ymax, zmax),
                vec3(xmin, ymin, zmin), vec3(xmax, ymin, zmin),
                vec3(xmin, ymax, zmin), vec3(xmax, ymax, zmin)
        };
        // The vertex indices of the twelve edges of the bounding box (each consecutive two numbers represent an edge).
        const std::vector<unsigned int> bbox_indices = {
                0, 1, 2, 3, 4, 5, 6, 7,
                0, 2, 4, 6, 1, 3, 5, 7,
                0, 4, 2, 6, 1, 5, 3, 7
        };
        // Upload the vertex positions of the bounding box to the GPU.
        update_vertex_buffer(bbox_points);
        // Upload the vertex indices of the bounding box to the GPU.
        update_element_buffer(bbox_indices);
    }
};
 
 
class MyPointsDrawable : public PointsDrawable {
public:
    MyPointsDrawable(const std::string& name = "") : PointsDrawable(name) {}
 
protected:
    void update_buffers_internal() {
        // The coordinates of the vertices.
        const std::vector<vec3> &points = resource::bunny_vertices;
        // Upload the vertex positions to the GPU.
        update_vertex_buffer(points);
    }
};
 
 
int main(int argc, char **argv) {
    // initialize Easy3D.
    initialize();
 
    //-------------------------------------------------------------
 
    // Create the default Easy3D viewer.
    // Note: a viewer must be created before creating any drawables.
    Viewer viewer(EXAMPLE_TITLE);
    viewer.set_usage("");
 
    //-------------------------------------------------------------
 
    // We visualize the "bunny".
 
    //-------------------------------------------------------------
    // Create a TrianglesDrawable to visualize the surface of the "bunny".
    // For visualization, the point positions and the vertex indices of the faces have to be sent to the GPU.
    auto surface = new MyTrianglesDrawable("faces");
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<MyTrianglesDrawable>(surface));
 
    //-------------------------------------------------------------
    // Create a PointsDrawable to visualize the vertices of the "bunny".
    // Only the vertex positions have to be sent to the GPU for visualization.
    auto vertices = new MyPointsDrawable("vertices");
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<MyPointsDrawable>(vertices));
    // Set a color for the vertices (here we want a red color).
    vertices->set_uniform_coloring(vec4(1.0f, 0.0f, 0.0f, 1.0f));  // r, g, b, a
    // Three options are available for visualizing points:
    //      - PLAIN: plain points (i.e., each point is a square on the screen);
    //      - SPHERE: each point is visualized a sphere;
    //      - SURFEL: each point is visualized an oriented disk.
    // In this example, let's render the vertices as spheres.
    vertices->set_impostor_type(PointsDrawable::SPHERE);
    // Set the vertices size (here 10 pixels).
    vertices->set_point_size(10);
 
    //-------------------------------------------------------------
    // Create a LinesDrawable to visualize the bounding box of the "bunny".
 
    // Compute the bounding box.
    auto bbox_drawable = new MyLinesDrawable("bbox");
    // Add the drawable to the viewer
    viewer.add_drawable(std::shared_ptr<MyLinesDrawable>(bbox_drawable));
    // Set a color for the edges of the bounding box (here we want a blue color).
    bbox_drawable->set_uniform_coloring(vec4(0.0f, 0.0f, 1.0f, 1.0f));    // r, g, b, a
    // Set the width of the edges (here 5 pixels).
    bbox_drawable->set_line_width(5.0f);
 
    //-------------------------------------------------------------
 
    // Make sure everything is within the visible region of the viewer.
    viewer.fit_screen();
 
    // run the viewer
    return viewer.run();
}
 
#endif