feat: cubic bezier bounding box

Captainfl4me · May 6, 2024 · 0b1af3e · 0b1af3e
1 parent 7f2a660
commit 0b1af3e
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Showing 2 changed files with 99 additions and 1 deletion.
diff --git a/src/bezier.rs b/src/bezier.rs
@@ -422,3 +422,77 @@ pub fn draw_bezier(points: &[impl PointGui], d: &mut RaylibDrawHandle, t: Option
         point.draw(d);
     }
 }
+
+pub fn cubic_bezier_bounding_box(points: &[impl Point]) -> Result<Rectangle, String> {
+    if points.len() != 4 {
+        return Err("Cubic Bezier curve needs 4 points".to_string());
+    }
+    let p0 = points[0].get_position();
+    let p1 = points[1].get_position();
+    let p2 = points[2].get_position();
+    let p3 = points[3].get_position();
+
+    let a = -p0 * 3.0 + p1 * 9.0 - p2 * 9.0 + p3 * 3.0;
+    let b = p0 * 6.0 - p1 * 12.0 + p2 * 6.0;
+    let c = -p0 * 3.0 + p1 * 3.0;
+
+    let mut bbs = vec![p0, p3]; // Possible bounding box points
+
+    if a.x == 0.0 {
+        if b.x != 0.0 {
+            let t = -c.x / b.x;
+            bbs.push(evalute_bezier_curve(points, t));
+        }
+    } else {
+        let x_delta = b.x * b.x - 4.0 * a.x * c.x;
+        if x_delta >= 0.0 {
+            let x_t_min = (-b.x - x_delta.sqrt()) / (2.0 * a.x);
+            let x_t_max = (-b.x + x_delta.sqrt()) / (2.0 * a.x);
+            bbs.push(evalute_bezier_curve(points, x_t_min.clamp(0.0, 1.0)));
+            bbs.push(evalute_bezier_curve(points, x_t_max.clamp(0.0, 1.0)));
+        }
+    }
+
+    if a.y == 0.0 {
+        if b.y != 0.0 {
+            let t = -c.y / b.y;
+            bbs.push(evalute_bezier_curve(points, t));
+        }
+    } else {
+        let y_delta = b.y * b.y - 4.0 * a.y * c.y;
+        if y_delta >= 0.0 {
+            let y_t_min = (-b.y - y_delta.sqrt()) / (2.0 * a.y);
+            let y_t_max = (-b.y + y_delta.sqrt()) / (2.0 * a.y);
+            bbs.push(evalute_bezier_curve(points, y_t_min.clamp(0.0, 1.0)));
+            bbs.push(evalute_bezier_curve(points, y_t_max.clamp(0.0, 1.0)));
+        }
+    }
+
+    let x_min: f32 = bbs
+        .iter()
+        .map(|bb| bb.x)
+        .min_by(|a, b| a.total_cmp(b))
+        .unwrap();
+    let x_max: f32 = bbs
+        .iter()
+        .map(|bb| bb.x)
+        .max_by(|a, b| a.total_cmp(b))
+        .unwrap();
+    let y_min: f32 = bbs
+        .iter()
+        .map(|bb| bb.y)
+        .min_by(|a, b| a.total_cmp(b))
+        .unwrap();
+    let y_max: f32 = bbs
+        .iter()
+        .map(|bb| bb.y)
+        .max_by(|a, b| a.total_cmp(b))
+        .unwrap();
+
+    Ok(Rectangle {
+        x: x_min,
+        y: y_min,
+        width: (x_min - x_max).abs(),
+        height: (y_min - y_max).abs(),
+    })
+}
diff --git a/src/main.rs b/src/main.rs
@@ -320,6 +320,7 @@ fn bezier_spline_scene(
     let mut animation_bounce = false;
     let mut has_point_selected = false;
     let mut debug_draw = true;
+    let mut draw_bounding_box = false;
     let mut lock_move = true;
     let mut clock_divider = 0;
     let mut is_closed_loop = false;
@@ -328,6 +329,7 @@ fn bezier_spline_scene(
     let left_slider_text = CStr::from_bytes_with_nul(b"0.0\0").unwrap();
     let right_slider_text = CStr::from_bytes_with_nul(b"1.0\0").unwrap();
     let animation_toggle_text = CStr::from_bytes_with_nul(b"Animate T value\0").unwrap();
+    let bounding_box_toggle_text = CStr::from_bytes_with_nul(b"Draw Bouding box\0").unwrap();
     let debug_text = CStr::from_bytes_with_nul(b"Activate debug draw\0").unwrap();
     let lock_move_text = CStr::from_bytes_with_nul(b"Lock points movement\0").unwrap();
     let mut current_draw_time_text = String::new();
@@ -496,9 +498,14 @@ fn bezier_spline_scene(
                 Some(animation_toggle_text),
                 &mut animated,
             );
+            rl_draw_handle.gui_toggle(
+                Rectangle::new(30.0, 110.0, 200.0, 25.0),
+                Some(bounding_box_toggle_text),
+                &mut draw_bounding_box,
+            );
         }
         rl_draw_handle.gui_toggle(
-            Rectangle::new(30.0, if debug_draw { 110.0 } else { 50.0 }, 200.0, 25.0),
+            Rectangle::new(30.0, if debug_draw { 140.0 } else { 50.0 }, 200.0, 25.0),
             Some(lock_move_text),
             &mut lock_move,
         );
@@ -514,6 +521,14 @@ fn bezier_spline_scene(
                 &mut rl_draw_handle,
                 if debug_draw { Some(t) } else { None },
             );
+            if draw_bounding_box {
+                if let Ok(bb) = cubic_bezier_bounding_box(&cubic_bezier_points) {
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x, bb.y), Vector2::new(bb.x + bb.width, bb.y), COLOR_RED);
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x + bb.width, bb.y), Vector2::new(bb.x + bb.width, bb.y + bb.height), COLOR_RED);
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x + bb.width, bb.y + bb.height), Vector2::new(bb.x, bb.y + bb.height), COLOR_RED);
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x, bb.y + bb.height), Vector2::new(bb.x, bb.y), COLOR_RED);
+                }
+            }
         }
         if is_closed_loop {
             let cubic_bezier_points = [
@@ -530,6 +545,15 @@ fn bezier_spline_scene(
                 &mut rl_draw_handle,
                 if debug_draw { Some(t) } else { None },
             );
+
+            if draw_bounding_box {
+                if let Ok(bb) = cubic_bezier_bounding_box(&cubic_bezier_points) {
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x, bb.y), Vector2::new(bb.x + bb.width, bb.y), COLOR_RED);
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x + bb.width, bb.y), Vector2::new(bb.x + bb.width, bb.y + bb.height), COLOR_RED);
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x + bb.width, bb.y + bb.height), Vector2::new(bb.x, bb.y + bb.height), COLOR_RED);
+                    rl_draw_handle.draw_line_v(Vector2::new(bb.x, bb.y + bb.height), Vector2::new(bb.x, bb.y), COLOR_RED);
+                }
+            }
         }
 
         if clock_divider == 0 {