application/005_pick_triangle/main.cpp

Copyright Matus Chochlik. Distributed under the Boost Software License, Version 1.0. See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt

#include <eagine/application/main.hpp>
#include <eagine/application_config.hpp>
#include <eagine/embed.hpp>
#include <eagine/timeout.hpp>
 
#include <oglplus/gl.hpp>
#include <oglplus/gl_api.hpp>
 
#include <eagine/math/intersection.hpp>
#include <oglplus/glsl/string_ref.hpp>
#include <oglplus/math/primitives.hpp>
#include <oglplus/math/vector.hpp>
 
namespace eagine::application {
//------------------------------------------------------------------------------
class example_picking : public application {
public:
    example_picking(execution_context&, video_context&);
 
    auto is_done() noexcept -> bool final {
        return _is_done.is_expired();
    }
 
    void on_video_resize() noexcept final;
    void update() noexcept final;
    void clean_up() noexcept final;
 
    void motion_x(const input&);
    void motion_y(const input&);
 
private:
    execution_context& _ctx;
    video_context& _video;
    timeout _is_done{std::chrono::seconds(10)};
 
    oglp::triangle tri{
      oglp::vec3{-0.2F, 0.5F, 0.0F},
      oglp::vec3{-0.7F, -0.6F, 0.0F},
      oglp::vec3{0.6F, 0.2F, 0.0F}};
 
    float x_pos{0.F};
    float y_pos{0.F};
    float hl_value{0.F};
    bool is_inside{false};
    bool has_moved{false};
 
    oglp::owned_vertex_array_name vao;
 
    oglp::owned_buffer_name positions;
 
    oglp::owned_program_name prog;
 
    oglp::uniform_location highlight_loc;
};
//------------------------------------------------------------------------------
example_picking::example_picking(execution_context& ec, video_context& vc)
  : _ctx{ec}
  , _video{vc} {
 
    auto& glapi = _video.gl_api();
    auto& [gl, GL] = glapi;
 
    gl.clear_color(0.4F, 0.4F, 0.4F, 0.0F);
 
    // vertex shader
    auto vs_source = embed(EAGINE_ID(VertShader), "vertex.glsl");
    oglp::owned_shader_name vs;
    gl.create_shader(GL.vertex_shader) >> vs;
    auto cleanup_vs = gl.delete_shader.raii(vs);
    gl.shader_source(vs, oglp::glsl_string_ref(vs_source));
    gl.compile_shader(vs);
 
    // fragment shader
    auto fs_source = embed(EAGINE_ID(FragShader), "fragment.glsl");
    oglp::owned_shader_name fs;
    gl.create_shader(GL.fragment_shader) >> fs;
    auto cleanup_fs = gl.delete_shader.raii(fs);
    gl.shader_source(fs, oglp::glsl_string_ref(fs_source));
    gl.compile_shader(fs);
 
    // program
    gl.create_program() >> prog;
    gl.attach_shader(prog, vs);
    gl.attach_shader(prog, fs);
    gl.link_program(prog);
    gl.use_program(prog);
 
    // vao
    gl.gen_vertex_arrays() >> vao;
    gl.bind_vertex_array(vao);
 
    // positions
    const auto position_data = GL.float_.array(
      tri.a().x(),
      tri.a().y(),
      tri.b().x(),
      tri.b().y(),
      tri.c().x(),
      tri.c().y());
 
    gl.gen_buffers() >> positions;
    gl.bind_buffer(GL.array_buffer, positions);
    gl.buffer_data(GL.array_buffer, view(position_data), GL.static_draw);
    oglp::vertex_attrib_location position_loc;
    gl.get_attrib_location(prog, "Position") >> position_loc;
 
    gl.vertex_attrib_pointer(position_loc, 2, GL.float_, GL.false_);
    gl.enable_vertex_attrib_array(position_loc);
 
    // uniform
    gl.get_uniform_location(prog, "Highlight") >> highlight_loc;
    glapi.set_uniform(prog, highlight_loc, hl_value);
 
    gl.disable(GL.depth_test);
 
    ec.connect_inputs()
      .map_inputs()
      .connect_input(
        EAGINE_MSG_ID(Example, MotionX),
        {this, EAGINE_THIS_MEM_FUNC_C(motion_x)})
      .map_input(
        EAGINE_MSG_ID(Example, MotionX),
        EAGINE_MSG_ID(Cursor, PositionX),
        input_setup().absolute_norm())
      .connect_input(
        EAGINE_MSG_ID(Example, MotionY),
        {this, EAGINE_THIS_MEM_FUNC_C(motion_y)})
      .map_input(
        EAGINE_MSG_ID(Example, MotionY),
        EAGINE_MSG_ID(Cursor, PositionY),
        input_setup().absolute_norm())
      .switch_input_mapping();
}
//------------------------------------------------------------------------------
void example_picking::on_video_resize() noexcept {
    auto& gl = _video.gl_api();
    gl.viewport(_video.surface_size());
}
//------------------------------------------------------------------------------
void example_picking::update() noexcept {
    auto& glapi = _video.gl_api();
    auto& [gl, GL] = glapi;
 
    if(has_moved) {
        oglp::line ray(
          oglp::vec3(x_pos, y_pos, 1.F), oglp::vec3(0.F, 0.F, -1.F));
 
        is_inside = bool(math::line_triangle_intersection(ray, tri));
        has_moved = false;
        _is_done.reset();
    }
 
    const auto dt = _ctx.state().frame_duration().value();
    if(is_inside) {
        hl_value = math::minimum(hl_value + dt * 3.0F, 1.F);
    } else {
        hl_value = math::maximum(hl_value - dt * 1.0F, 0.F);
    }
    glapi.set_uniform(prog, highlight_loc, hl_value);
 
    gl.clear(GL.color_buffer_bit);
    gl.draw_arrays(GL.triangles, 0, 3);
 
    _video.commit();
}
//------------------------------------------------------------------------------
void example_picking::clean_up() noexcept {
    auto& gl = _video.gl_api();
 
    gl.delete_program(std::move(prog));
    gl.delete_buffers(std::move(positions));
    gl.delete_vertex_arrays(std::move(vao));
 
    _video.end();
}
//------------------------------------------------------------------------------
void example_picking::motion_x(const input& i) {
    x_pos = float(2 * i.get());
    has_moved = true;
}
//------------------------------------------------------------------------------
void example_picking::motion_y(const input& i) {
    y_pos = float(2 * i.get());
    has_moved = true;
}
//------------------------------------------------------------------------------
class example_launchpad : public launchpad {
public:
    auto setup(main_ctx&, launch_options& opts) -> bool final {
        opts.no_audio().require_input().require_video();
        return true;
    }
 
    auto check_requirements(video_context& vc) -> bool {
        auto& [gl, GL] = vc.gl_api();
 
        return gl.disable && gl.clear_color && gl.create_shader &&
               gl.shader_source && gl.compile_shader && gl.create_program &&
               gl.attach_shader && gl.link_program && gl.use_program &&
               gl.gen_buffers && gl.bind_buffer && gl.buffer_data &&
               gl.gen_vertex_arrays && gl.bind_vertex_array &&
               gl.get_attrib_location && gl.vertex_attrib_pointer &&
               gl.enable_vertex_attrib_array && gl.draw_arrays &&
               GL.vertex_shader && GL.fragment_shader;
    }
 
    auto launch(execution_context& ec, const launch_options&)
      -> std::unique_ptr<application> final {
        if(auto opt_vc{ec.video_ctx()}) {
            auto& vc = extract(opt_vc);
            vc.begin();
            if(vc.init_gl_api()) {
                if(check_requirements(vc)) {
                    return {std::make_unique<example_picking>(ec, vc)};
                }
            }
        }
        return {};
    }
};
//------------------------------------------------------------------------------
auto establish(main_ctx&) -> std::unique_ptr<launchpad> {
    return {std::make_unique<example_launchpad>()};
}
//------------------------------------------------------------------------------
} // namespace eagine::application