feat: render a large grid of point-particles as billboards with program point size enabled

shaders/simple.vert

@@ -3,7 +3,7 @@
 in layout(location=0) vec3 position;
 in layout(location=1) vec4 aColor;
 out vec4 vColor;
-uniform mat4 transform;
+layout(location = 0) uniform mat4 transform;
 
 void main() {
     gl_Position = transform * vec4(position, 1.0f);

src/main.rs

@@ -163,6 +163,7 @@ fn main() {
             gl::Disable(gl::MULTISAMPLE);
             gl::Enable(gl::BLEND);
             gl::BlendFunc(gl::SRC_ALPHA, gl::ONE_MINUS_SRC_ALPHA);
+            gl::Enable(gl::PROGRAM_POINT_SIZE);
             gl::Enable(gl::DEBUG_OUTPUT_SYNCHRONOUS);
             gl::DebugMessageCallback(Some(util::debug_callback), ptr::null());
 
@@ -220,6 +221,40 @@ fn main() {
 
         let my_vao = unsafe { create_vao(&vertices, &colors, &indices) };
 
+        let billboard_vertices = vec![
+            -0.5, -0.5, 0.0,
+            -0.5,  0.5, 0.0,
+             0.5,  0.5, 0.0,
+             0.5, -0.5, 0.0,
+        ];
+        let billboard_indices = vec![
+            0, 1, 2,
+            0, 2, 3,
+        ];
+        let billboard_colors = vec![
+            1.0, 1.0, 1.0, 1.0,
+            1.0, 1.0, 1.0, 1.0,
+            1.0, 1.0, 1.0, 1.0,
+            1.0, 1.0, 1.0, 1.0,
+        ];
+        let billboard_vao = unsafe { create_vao(&billboard_vertices, &billboard_colors, &billboard_indices) };
+
+        // Generate a grid of point‐particles
+        let grid_size = 200;
+        let mut particle_vertices = Vec::with_capacity(grid_size * grid_size * 3);
+        let mut particle_colors   = Vec::with_capacity(grid_size * grid_size * 4);
+        for i in 0..grid_size {
+            for j in 0..grid_size {
+                let x = (i as f32 / grid_size as f32 - 0.5) * 20.0;
+                let y = (j as f32 / grid_size as f32 - 0.5) * 20.0;
+                let z = -5.0;
+                particle_vertices.extend_from_slice(&[x, y, z]);
+                particle_colors.extend_from_slice(&[1.0, 1.0, 1.0, 1.0]);
+            }
+        }
+        let particle_vao   = unsafe { create_vao(&particle_vertices, &particle_colors, &Vec::new()) };
+        let particle_count = (grid_size * grid_size) as i32;
+
         // == // Set up your shaders here
 
         // Basic usage of shader helper:
@@ -242,6 +277,11 @@ fn main() {
         // Used to demonstrate keyboard handling for exercise 2.
         let mut _arbitrary_number = 0.0; // feel free to remove
 
+        // camera position (x, y, z) and orientation (yaw, pitch)
+        let mut cam_pos: glm::Vec3 = glm::vec3(0.0, 0.0, 0.0);
+        let mut cam_yaw: f32 = 0.0;
+        let mut cam_pitch: f32 = 0.0;
+
         // The main rendering loop
         let first_frame_time = std::time::Instant::now();
         let mut previous_frame_time = first_frame_time;
@@ -265,23 +305,38 @@ fn main() {
                 }
             }
 
-            // Handle keyboard input
+            // Handle keyboard input for camera movement and rotation
             if let Ok(keys) = pressed_keys.lock() {
+                // movement speed
+                let speed = 2.5 * delta_time;
+                // camera direction vectors based on yaw & pitch
+                let front = glm::vec3(
+                    cam_yaw.sin() * cam_pitch.cos(),
+                    cam_pitch.sin(),
+                    -cam_yaw.cos() * cam_pitch.cos(),
+                );
+                let right = glm::normalize(&glm::cross(&front, &glm::vec3(0.0, 1.0, 0.0)));
+                let up_vec = glm::normalize(&glm::cross(&right, &front));
                 for key in keys.iter() {
                     match key {
-                        // The `VirtualKeyCode` enum is defined here:
-                        //    https://docs.rs/winit/0.25.0/winit/event/enum.VirtualKeyCode.html
-                        VirtualKeyCode::A => {
-                            _arbitrary_number += delta_time;
-                        }
-                        VirtualKeyCode::D => {
-                            _arbitrary_number -= delta_time;
-                        }
-
-                        // default handler:
+                        // Move relative to camera orientation
+                        VirtualKeyCode::W => { cam_pos += front * speed; }
+                        VirtualKeyCode::S => { cam_pos -= front * speed; }
+                        VirtualKeyCode::A => { cam_pos -= right * speed; }
+                        VirtualKeyCode::D => { cam_pos += right * speed; }
+                        VirtualKeyCode::Space => { cam_pos += up_vec * speed; }
+                        VirtualKeyCode::LShift => { cam_pos -= up_vec * speed; }
+                        // Rotation: adjust yaw and pitch
+                        VirtualKeyCode::Left  => { cam_yaw   -= delta_time; }
+                        VirtualKeyCode::Right => { cam_yaw   += delta_time; }
+                        VirtualKeyCode::Up    => { cam_pitch += delta_time; }
+                        VirtualKeyCode::Down  => { cam_pitch -= delta_time; }
                         _ => {}
                     }
                 }
+                // clamp pitch to avoid flipping
+                let pitch_limit = std::f32::consts::FRAC_PI_2 - 0.01;
+                cam_pitch = cam_pitch.clamp(-pitch_limit, pitch_limit);
             }
             // Handle mouse movement. delta contains the x and y movement of the mouse since last frame in pixels
             if let Ok(mut delta) = mouse_delta.lock() {
@@ -300,21 +355,34 @@ fn main() {
 
                 // == // Issue the necessary gl:: commands to draw your scene here
                 simple_shader.activate();
-                // build and send the transform matrix (start from identity)
-                let mut transform: glm::Mat4 = glm::identity();
+                // build Model matrix (start from identity)
+                let mut model: glm::Mat4 = glm::identity();
                 // cycle through each transform parameter (a,b,c,d,e,f) over time
                 let cycle_duration = 2.0;
                 let idx = ((elapsed / cycle_duration).floor() as usize) % 6;
                 let v = elapsed.sin();
                 match idx {
-                    0 => transform[(0,0)] = v, // a
-                    1 => transform[(0,1)] = v, // b
-                    2 => transform[(0,3)] = v, // c
-                    3 => transform[(1,0)] = v, // d
-                    4 => transform[(1,1)] = v, // e
-                    5 => transform[(1,3)] = v, // f
+                    0 => model[(0,0)] = v, // a
+                    1 => model[(0,1)] = v, // b
+                    2 => model[(0,3)] = v, // c
+                    3 => model[(1,0)] = v, // d
+                    4 => model[(1,1)] = v, // e
+                    5 => model[(1,3)] = v, // f
                     _ => {}
                 }
+                // model translation to initial view distance
+                let translation_model: glm::Mat4 = glm::translation(&glm::vec3(0.0, 0.0, -5.0));
+                let model = translation_model * model;
+                // build View matrix: translate and rotate world relative to camera
+                let view_translation: glm::Mat4 = glm::translation(&(-cam_pos));
+                let view_rot_y: glm::Mat4 = glm::rotation(-cam_yaw, &glm::vec3(0.0, 1.0, 0.0));
+                let view_rot_x: glm::Mat4 = glm::rotation(-cam_pitch, &glm::vec3(1.0, 0.0, 0.0));
+                let view: glm::Mat4 = view_rot_x * view_rot_y * view_translation;
+                // build Projection matrix
+                let projection: glm::Mat4 =
+                    glm::perspective(window_aspect_ratio, std::f32::consts::PI / 4.0, 1.0, 100.0);
+                // final transform: Projection * View * Model
+                let transform: glm::Mat4 = projection * view * model;
                 gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, transform.as_ptr());
                 gl::BindVertexArray(my_vao);
                 gl::DrawElements(
@@ -323,6 +391,27 @@ fn main() {
                     gl::UNSIGNED_INT,
                     std::ptr::null(),
                 );
+
+                // Draw point‐particles
+                let transform_particles = projection * view * glm::identity();
+                gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, transform_particles.as_ptr());
+                gl::BindVertexArray(particle_vao);
+                gl::DrawArrays(gl::POINTS, 0, particle_count);
+
+                // Draw billboard (camera-facing quad)
+                let translation_bill = glm::translation(&glm::vec3(0.0, 0.0, -2.0));
+                let inv_rot_y = glm::rotation(cam_yaw, &glm::vec3(0.0, 1.0, 0.0));
+                let inv_rot_x = glm::rotation(cam_pitch, &glm::vec3(1.0, 0.0, 0.0));
+                let model_billboard = translation_bill * inv_rot_y * inv_rot_x;
+                let transform_bill = projection * view * model_billboard;
+                gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, transform_bill.as_ptr());
+                gl::BindVertexArray(billboard_vao);
+                gl::DrawElements(
+                    gl::TRIANGLES,
+                    billboard_indices.len() as i32,
+                    gl::UNSIGNED_INT,
+                    std::ptr::null(),
+                );
             }
 
             // Display the new color buffer on the display