glium 0.29.1

Elegant and safe OpenGL wrapper. Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API. Its objectives: - Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium. - Provide an API that enforces good pratices such as RAII or stateless function calls. - Be compatible with all OpenGL versions that support shaders, providing unified API when things diverge. - Avoid all OpenGL errors beforehand. - Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.
Documentation
#[macro_use]
extern crate glium;

#[allow(unused_imports)]
use glium::{glutin, Surface};

mod support;

#[derive(Copy, Clone, Debug)]
struct PerInstance {
    pub id: u32,
    pub w_position: (f32, f32, f32),
    pub color: (f32, f32, f32),
}
implement_vertex!(PerInstance, id, w_position, color);

fn main() {
    // building the display, ie. the main object
    let event_loop = glutin::event_loop::EventLoop::new();
    let wb = glutin::window::WindowBuilder::new();
    let cb = glutin::ContextBuilder::new().with_depth_buffer(24);
    let display = glium::Display::new(wb, cb, &event_loop).unwrap();

    // building the vertex and index buffers
    let vertex_buffer = support::load_wavefront(&display, include_bytes!("support/teapot.obj"));

    // the program
    let program = program!(&display,
        140 => {
            vertex: "
                #version 140

                uniform mat4 persp_matrix;
                uniform mat4 view_matrix;

                in uint id;
                in vec3 w_position;
                in vec3 color;
                in vec3 position;
                in vec3 normal;
                out vec3 v_normal;
                out vec3 v_color;

                void main() {
                    v_normal = normal;
                    v_color = color;
                    gl_Position = persp_matrix * view_matrix * vec4(position * 0.005 + w_position, 1.0);
                }
            ",

            fragment: "
                #version 140

                in vec3 v_normal;
                in vec3 v_color;
                out vec4 f_color;

                const vec3 LIGHT = vec3(-0.2, 0.8, 0.1);

                void main() {
                    float lum = max(dot(normalize(v_normal), normalize(LIGHT)), 0.0);
                    vec3 color = (0.3 + 0.7 * lum) * v_color;
                    f_color = vec4(color, 1.0);
                }
            ",
        },
    ).unwrap();

    // the picking program
    let picking_program = program!(&display,
        140 => {
            vertex: "
                #version 140

                uniform mat4 persp_matrix;
                uniform mat4 view_matrix;

                in uint id;
                in vec3 w_position;
                in vec3 color;
                in vec3 position;
                in vec3 normal;
                flat out uint v_id;

                void main() {
                    v_id = id;
                    gl_Position = persp_matrix * view_matrix * vec4(position * 0.005 + w_position, 1.0);
                }
            ",

            fragment: "
                #version 140

                flat in uint v_id;
                out uint f_id;

                void main() {
                    f_id = v_id;
                }
            ",
        },
    ).unwrap();

    let mut camera = support::camera::CameraState::new();
    camera.set_position((0.0, 0.0, -1.5));
    camera.set_direction((0.0, 0.0, 1.0));

    //id's must be unique and != 0
    let mut per_instance = vec![
        PerInstance { id: 1, w_position: (-1.0, 0.0, 0.0), color: (1.0, 0.0, 0.0)},
        PerInstance { id: 2, w_position: ( 0.0, 0.0, 0.0), color: (1.0, 0.0, 0.0)},
        PerInstance { id: 3, w_position: ( 1.0, 0.0, 0.0), color: (1.0, 0.0, 0.0)},
    ];
    per_instance.sort_by(|a, b| a.id.cmp(&b.id));
    let original = per_instance.clone();

    let mut picking_attachments: Option<(glium::texture::UnsignedTexture2d, glium::framebuffer::DepthRenderBuffer)> = None;
    let picking_pbo: glium::texture::pixel_buffer::PixelBuffer<u32>
        = glium::texture::pixel_buffer::PixelBuffer::new_empty(&display, 1);


    let mut cursor_position: Option<(i32, i32)> = None;

    // the main loop
    support::start_loop(event_loop, move |events| {
        camera.update();


        // determine which object has been picked at the previous frame
        let picked_object = {
            let data = picking_pbo.read().map(|d| d[0]).unwrap_or(0);
            if data != 0 {
                per_instance.binary_search_by(|x| x.id.cmp(&data)).ok()
            } else {
                None
            }
        };

        per_instance = original.clone();
        if let Some(index) = picked_object {
            per_instance[index as usize] = PerInstance {
                id: per_instance[index as usize].id,
                w_position: per_instance[index as usize].w_position,
                color: (0.0, 1.0, 0.0)
            };
        }

        // building the uniforms
        let uniforms = uniform! {
            persp_matrix: camera.get_perspective(),
            view_matrix: camera.get_view(),
        };

        // draw parameters
        let params = glium::DrawParameters {
            depth: glium::Depth {
                test: glium::DepthTest::IfLess,
                write: true,
                .. Default::default()
            },
            .. Default::default()
        };

        let per_instance_buffer = glium::vertex::VertexBuffer::new(&display, &per_instance).unwrap();

        // drawing a frame
        let mut target = display.draw();
        target.clear_color_and_depth((0.0, 0.0, 0.0, 0.0), 1.0);

        //update picking texture
        if picking_attachments.is_none() || (
            picking_attachments.as_ref().unwrap().0.get_width(),
            picking_attachments.as_ref().unwrap().0.get_height().unwrap()
        ) != target.get_dimensions() {
            let (width, height) = target.get_dimensions();
            picking_attachments = Some((
                glium::texture::UnsignedTexture2d::empty_with_format(
                    &display,
                    glium::texture::UncompressedUintFormat::U32,
                    glium::texture::MipmapsOption::NoMipmap,
                    width, height,
                ).unwrap(),
                glium::framebuffer::DepthRenderBuffer::new(
                    &display,
                    glium::texture::DepthFormat::F32,
                    width, height,
                ).unwrap()
            ))
        }

        // drawing the models and pass the picking texture
        if let Some((ref picking_texture, ref depth_buffer)) = picking_attachments {
            //clearing the picking texture
            picking_texture.main_level().first_layer().into_image(None).unwrap().raw_clear_buffer([0u32, 0, 0, 0]);

            let mut picking_target = glium::framebuffer::SimpleFrameBuffer::with_depth_buffer(&display, picking_texture, depth_buffer).unwrap();
            picking_target.clear_depth(1.0);
            picking_target.draw((&vertex_buffer, per_instance_buffer.per_instance().unwrap()),
                        &glium::index::NoIndices(glium::index::PrimitiveType::TrianglesList),
                        &picking_program, &uniforms, &params).unwrap();
        }
        target.draw((&vertex_buffer, per_instance_buffer.per_instance().unwrap()),
                    &glium::index::NoIndices(glium::index::PrimitiveType::TrianglesList),
                    &program, &uniforms, &params).unwrap();
        target.finish().unwrap();


        // committing into the picking pbo
        if let (Some(cursor), Some(&(ref picking_texture, _))) = (cursor_position, picking_attachments.as_ref()) {
            let read_target = glium::Rect {
                left: (cursor.0 - 1) as u32,
                bottom: picking_texture.get_height().unwrap().saturating_sub(std::cmp::max(cursor.1 - 1, 0) as u32),
                width: 1,
                height: 1,
            };

            if read_target.left < picking_texture.get_width()
            && read_target.bottom < picking_texture.get_height().unwrap() {
                picking_texture.main_level()
                    .first_layer()
                    .into_image(None).unwrap()
                    .raw_read_to_pixel_buffer(&read_target, &picking_pbo);
            } else {
                picking_pbo.write(&[0]);
            }
        } else {
            picking_pbo.write(&[0]);
        }

        let mut action = support::Action::Continue;

        // polling and handling the events received by the window
        for event in events {
            match event {
                glutin::event::Event::WindowEvent { event, .. } => match event {
                    glutin::event::WindowEvent::CloseRequested => action = support::Action::Stop,
                    glutin::event::WindowEvent::CursorMoved { position, .. } => {
                        cursor_position = Some(position.cast::<i32>().into());
                    }
                    ev => camera.process_input(&ev),
                },
                _ => (),
            }
        };

        action
    });
}