Significantly improve stroke smoothing and pressure handling. "Fix" issue with underallocation of WASM memory by doubling the size

client/math.js

@@ -60,20 +60,24 @@ function process_rdp_indices(state, zoom, stroke) {
     return npoints;
 }
 
-function process_ewmv(points, round = false) {
-    const result = [];
+function exponential_smoothing(points, last, up_to) {
     const alpha = 0.5;
 
-    result.push(points[0]);
+    let pr = 0;
 
-    for (let i = 1; i < points.length; ++i) {
+    let start = points.length - up_to;
+    if (start < 0) {
+        start = 0;
+    }
+
+    for (let i = start; i < points.length; ++i) {
         const p = points[i];
-        const x = Math.round(alpha * p.x + (1 - alpha) * result[result.length - 1].x);
-        const y = Math.round(alpha * p.y + (1 - alpha) * result[result.length - 1].y);
-        result.push({'x': x, 'y': y});
+        pr = alpha * p.pressure + (1 - alpha) * pr;
     }
 
-    return result;
+    pr = alpha * last.pressure + (1 - alpha) * pr;
+
+    return pr;
 }
 
 function process_stroke(state, zoom, stroke) {
@@ -92,7 +96,7 @@ function process_stroke(state, zoom, stroke) {
 }
 
 function rdp_find_max2(zoom, points, start, end) {
-    const EPS = 1.0 / zoom;
+    const EPS = 0.125 / zoom;
 
     let result = -1;
     let max_dist = 0;
@@ -107,7 +111,7 @@ function rdp_find_max2(zoom, points, start, end) {
     const sin_theta = dy / dist_ab;
     const cos_theta = dx / dist_ab;
 
-    for (let i = start; i < end; ++i) {
+    for (let i = start + 1; i < end; ++i) {
         const p = points[i];
         
         const ox = p.x - a.x;
@@ -145,9 +149,48 @@ function process_rdp_r2(zoom, points, start, end) {
 }
 
 function process_rdp2(zoom, points) {
-    const result = process_rdp_r2(zoom, points, 0, points.length - 1);
-    result.unshift(points[0]);
+    const result = [];
+    const stack = [];
+
+    stack.push({
+        'type': 0,
+        'start': 0,
+        'end': points.length - 1,
+    });
+
+    result.push(points[0]);
+
+    while (stack.length > 0) {
+        const entry = stack.pop();
+
+        if (entry.type === 0) {
+            const max = rdp_find_max2(zoom, points, entry.start, entry.end);
+
+            if (max !== -1) {
+                stack.push({
+                    'type': 0,
+                    'start': max,
+                    'end': entry.end
+                });
+
+                stack.push({
+                    'type': 1,
+                    'index': max,
+                });
+
+                stack.push({
+                    'type': 0,
+                    'start': entry.start,
+                    'end': max,
+                });
+            }
+        } else {
+            result.push(points[entry.index]);
+        }
+    }
+
     result.push(points[points.length - 1]);
+
     return result;
 }
 

client/speed.js

@@ -120,8 +120,9 @@ function wasm_ensure_by(state, nstrokes, ncoords) {
 
     if (realloc) {
         const current_pages = Math.ceil(state.wasm.memory.buffer.byteLength / (4096 * 16));
-        const need_pages = Math.ceil((state.wasm.coords_bytes * 3 + state.wasm.stroke_bytes * 2) / (4096 * 16)); // TODO: figure out actual memory requirements
+        const need_pages = 2 * Math.ceil((state.wasm.coords_bytes * 3 + state.wasm.stroke_bytes * 2) / (4096 * 16)); // TODO: figure out actual memory requirements
         const grow_by = Math.max(1, need_pages - current_pages);
+        // const grow_by = 16;
 
         state.wasm.memory.grow(grow_by);
         state.wasm.exports.free_static();

client/wasm/lod.c

@@ -220,6 +220,7 @@ do_lod(int *clipped_indices, int clipped_count, float zoom,
     
     int segments_head = 0;
     int stack[4096]; // TODO: what's a reasonable max size for this?
+    int max_stack_size = 0;
     
     for (int i = 0; i < clipped_count; ++i) {
         int stroke_index = clipped_indices[i];
@@ -243,6 +244,7 @@ do_lod(int *clipped_indices, int clipped_count, float zoom,
         stack[stack_head++] = point_count - 1;
         
         while (stack_head > 0) {
+            if (stack_head > max_stack_size) { max_stack_size = stack_head; }
             int end = stack[--stack_head];
             int start = stack[--stack_head];
             int type = stack[--stack_head];

client/webgl_geometry.js

@@ -151,10 +151,39 @@ function recompute_dynamic_data(state, context) {
     context.dynamic_stroke_count = total_strokes;
 }
 
+let _head = null;
+
 function geometry_add_point(state, context, player_id, point) {
     if (!state.online) return;
-    state.players[player_id].points.push(point);
+
+    const points = state.players[player_id].points;
+
+    if (false && points.length === 1) {
+        // Fix up pressure of first point to get rid of ugly spike bit
+        const first_point = points[0];
+        if (first_point.pressure === 0) {
+            first_point.pressure = point.pressure;
+        }
+    }
+
+    if (points.length > 0) {
+        // pulled from "perfect-freehand" package. MIT
+        // https://github.com/steveruizok/perfect-freehand/
+        const streamline = 0.5;
+        const t = 0.15 + (1 - streamline) * 0.85
+        const smooth_pressure = exponential_smoothing(points, point, 3);
+        points.push({
+            'x': _head.x * t + point.x * (1 - t),
+            'y': _head.y * t + point.y * (1 - t),
+            'pressure': _head.pressure * t + smooth_pressure * (1 - t),
+        });
+        point.pressure = smooth_pressure;
+    } else {
+        state.players[player_id].points.push(point);
+    }
+    
     recompute_dynamic_data(state, context);
+    _head = point;
 }
 
 function geometry_clear_player(state, context, player_id) {

client/webgl_listeners.js

@@ -210,7 +210,7 @@ function mousedown(e, state, context) {
     }
 
     if (state.tools.active === 'pencil') {
-        canvasp.pressure = 128;
+        canvasp.pressure = Math.ceil(e.pressure * 255);
         geometry_clear_player(state, context, state.me);
         geometry_add_point(state, context, state.me, canvasp);
 
@@ -249,9 +249,10 @@ function mousemove(e, state, context) {
     if (state.me in state.players) {
         const me = state.players[state.me];
         const width = Math.max(me.width * state.canvas.zoom, 2.0);
-        const brush_x = screenp.x - width / 2 - 2;
-        const brush_y = screenp.y - width / 2 - 2; 
-        document.querySelector('.brush-dom').style.transform = `translate(${Math.round(brush_x)}px, ${Math.round(brush_y)}px)`; 
+        const radius = Math.round(width / 2);
+        const brush_x = screenp.x - radius - 2;
+        const brush_y = screenp.y - radius - 2; 
+        document.querySelector('.brush-dom').style.transform = `translate(${brush_x}px, ${brush_y}px)`; 
     }
 
     if (state.me in state.players && dist_v2(state.players[state.me].cursor, canvasp) > 5) {
@@ -376,7 +377,7 @@ function update_cursor(state) {
     const me = state.players[state.me];
 
     const width = Math.max(me.width * state.canvas.zoom, 2.0);
-    const radius = width / 2;
+    const radius = Math.round(width / 2);
     const current_color = color_from_u32(me.color); 
     const stroke = (me.color === 0xFFFFFF ? 'black' : 'white');
     const svg = `<svg style="display: block" xmlns="http://www.w3.org/2000/svg" width="${width + 4}" height="${width + 4}">