Freedraw experiment 1

packages/element/src/bounds.ts

@@ -5,6 +5,7 @@ import {
   invariant,
   rescalePoints,
   sizeOf,
+  STROKE_WIDTH,
 } from "@excalidraw/common";
 
 import {
@@ -832,9 +833,15 @@ export const getArrowheadPoints = (
   // This value is selected by minimizing a minimum size with the last segment of the arrowhead
   const lengthMultiplier =
     arrowhead === "diamond" || arrowhead === "diamond_outline" ? 0.25 : 0.5;
-  const minSize = Math.min(size, length * lengthMultiplier);
-  const xs = x2 - nx * minSize;
-  const ys = y2 - ny * minSize;
+  // make arrowheads bigger for thick strokes
+  const strokeWidthMultiplier =
+    element.strokeWidth >= STROKE_WIDTH.extraBold ? 1.5 : 1;
+
+  const adjustedSize =
+    Math.min(size, length * lengthMultiplier) * strokeWidthMultiplier;
+
+  const xs = x2 - nx * adjustedSize;
+  const ys = y2 - ny * adjustedSize;
 
   if (
     arrowhead === "dot" ||
@@ -883,7 +890,7 @@ export const getArrowheadPoints = (
       const [px, py] = element.points.length > 1 ? element.points[1] : [0, 0];
 
       [ox, oy] = pointRotateRads(
-        pointFrom(x2 + minSize * 2, y2),
+        pointFrom(x2 + adjustedSize * 2, y2),
         pointFrom(x2, y2),
         Math.atan2(py - y2, px - x2) as Radians,
       );
@@ -894,7 +901,7 @@ export const getArrowheadPoints = (
           : [0, 0];
 
       [ox, oy] = pointRotateRads(
-        pointFrom(x2 - minSize * 2, y2),
+        pointFrom(x2 - adjustedSize * 2, y2),
         pointFrom(x2, y2),
         Math.atan2(y2 - py, x2 - px) as Radians,
       );

packages/element/src/freedraw.ts

@@ -0,0 +1,278 @@
+import { LaserPointer, type Point } from "@excalidraw/laser-pointer";
+
+import { clamp, round, type LocalPoint } from "@excalidraw/math";
+
+import getStroke from "perfect-freehand";
+
+import type { StrokeOptions } from "perfect-freehand";
+
+import type { ExcalidrawFreeDrawElement, PointerType } from "./types";
+
+export const STROKE_OPTIONS: Record<
+  PointerType | "default",
+  { streamline: number; simplify: number }
+> = {
+  default: {
+    streamline: 0.35,
+    simplify: 0.1,
+  },
+  mouse: {
+    streamline: 0.6,
+    simplify: 0.1,
+  },
+  pen: {
+    // for optimal performance, we use a lower streamline and simplify
+    streamline: 0.2,
+    simplify: 0.1,
+  },
+  touch: {
+    streamline: 0.65,
+    simplify: 0.1,
+  },
+} as const;
+
+export const getFreedrawConfig = (eventType: string | null | undefined) => {
+  return (
+    STROKE_OPTIONS[(eventType as PointerType | null) || "default"] ||
+    STROKE_OPTIONS.default
+  );
+};
+
+/**
+ * Calculates simulated pressure based on velocity between consecutive points.
+ * Fast movement (large distances) -> lower pressure
+ * Slow movement (small distances) -> higher pressure
+ */
+const calculateVelocityBasedPressure = (
+  points: readonly LocalPoint[],
+  index: number,
+  fixedStrokeWidth: boolean | undefined,
+  maxDistance = 8, // Maximum expected distance for normalization
+): number => {
+  if (fixedStrokeWidth) {
+    return 1;
+  }
+
+  // First point gets highest pressure
+  // This avoid "a dot followed by a line" effect, •== when first stroke is "slow"
+  if (index === 0) {
+    return 1;
+  }
+
+  const [x1, y1] = points[index - 1];
+  const [x2, y2] = points[index];
+
+  // Calculate distance between consecutive points
+  const distance = Math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2);
+
+  // Normalize distance and invert for pressure (0 = fast/low pressure, 1 = slow/high pressure)
+  const normalizedDistance = Math.min(distance / maxDistance, 1);
+  const basePressure = Math.max(0.1, 1 - normalizedDistance * 0.7); // Range: 0.1 to 1.0
+
+  const constantPressure = 0.5;
+  const pressure = constantPressure + (basePressure - constantPressure);
+
+  return Math.max(0.1, Math.min(1.0, pressure));
+};
+
+export const getFreedrawStroke = (element: ExcalidrawFreeDrawElement) => {
+  // Compose points as [x, y, pressure]
+  let points: [number, number, number][];
+  if (element.freedrawOptions?.fixedStrokeWidth) {
+    points = element.points.map(
+      ([x, y]: LocalPoint): [number, number, number] => [x, y, 1],
+    );
+  } else if (element.simulatePressure) {
+    // Simulate pressure based on velocity between consecutive points
+    points = element.points.map(([x, y]: LocalPoint, i) => [
+      x,
+      y,
+      calculateVelocityBasedPressure(
+        element.points,
+        i,
+        element.freedrawOptions?.fixedStrokeWidth,
+      ),
+    ]);
+  } else {
+    points = element.points.map(([x, y]: LocalPoint, i) => {
+      const rawPressure = element.pressures?.[i] ?? 0.5;
+
+      const amplifiedPressure = Math.pow(rawPressure, 0.6);
+      const adjustedPressure = amplifiedPressure;
+
+      return [x, y, clamp(adjustedPressure, 0.1, 1.0)];
+    });
+  }
+
+  const streamline =
+    element.freedrawOptions?.streamline ?? STROKE_OPTIONS.default.streamline;
+  const simplify =
+    element.freedrawOptions?.simplify ?? STROKE_OPTIONS.default.simplify;
+
+  const laser = new LaserPointer({
+    size: element.strokeWidth,
+    streamline,
+    simplify,
+    sizeMapping: ({ pressure: t }) => {
+      if (element.freedrawOptions?.fixedStrokeWidth) {
+        return 0.6;
+      }
+
+      if (element.simulatePressure) {
+        return 0.2 + t * 0.6;
+      }
+
+      return 0.2 + t * 0.8;
+    },
+  });
+
+  for (const pt of points) {
+    laser.addPoint(pt);
+  }
+  laser.close();
+
+  return laser.getStrokeOutline();
+};
+
+/**
+ * Generates an SVG path for a freedraw element using LaserPointer logic.
+ * Uses actual pressure data if available, otherwise simulates pressure based on velocity.
+ * No streamline, smoothing, or simulation is performed.
+ */
+export const getFreeDrawSvgPath = (
+  element: ExcalidrawFreeDrawElement,
+): string => {
+  // legacy, for backwards compatibility
+  if (element.freedrawOptions === null) {
+    return _legacy_getFreeDrawSvgPath(element);
+  }
+
+  return _transition_getFreeDrawSvgPath(element);
+
+  // return getSvgPathFromStroke(getFreedrawStroke(element));
+};
+
+const roundPoint = (A: Point): string => {
+  return `${round(A[0], 4, "round")},${round(A[1], 4, "round")} `;
+};
+
+const average = (A: Point, B: Point): string => {
+  return `${round((A[0] + B[0]) / 2, 4, "round")},${round(
+    (A[1] + B[1]) / 2,
+    4,
+    "round",
+  )} `;
+};
+
+export const getSvgPathFromStroke = (points: Point[]): string => {
+  const len = points.length;
+
+  if (len < 2) {
+    return "";
+  }
+
+  let a = points[0];
+  let b = points[1];
+
+  if (len === 2) {
+    return `M${roundPoint(a)}L${roundPoint(b)}`;
+  }
+
+  let result = "";
+
+  for (let i = 2, max = len - 1; i < max; i++) {
+    a = points[i];
+    b = points[i + 1];
+    result += average(a, b);
+  }
+
+  return `M${roundPoint(points[0])}Q${roundPoint(points[1])}${average(
+    points[1],
+    points[2],
+  )}${points.length > 3 ? "T" : ""}${result}L${roundPoint(points[len - 1])}`;
+};
+
+function _transition_getFreeDrawSvgPath(element: ExcalidrawFreeDrawElement) {
+  const inputPoints = element.simulatePressure
+    ? element.points
+    : element.points.length
+    ? element.points.map(([x, y], i) => [x, y, element.pressures[i]])
+    : [[0, 0, 0.5]];
+
+  // Consider changing the options for simulated pressure vs real pressure
+  const options: StrokeOptions = {
+    simulatePressure: element.simulatePressure,
+    size: element.strokeWidth,
+    thinning: 0.6,
+    smoothing: 0.5,
+    streamline: 0.5,
+    easing: (t) => {
+      if (element.freedrawOptions?.fixedStrokeWidth) {
+        return 0.5;
+      }
+
+      return Math.sin((t * Math.PI) / 2) * 0.65;
+    }, // https://easings.net/#easeOutSine
+    last: !!element.lastCommittedPoint, // LastCommittedPoint is added on pointerup
+  };
+
+  return _legacy_getSvgPathFromStroke(
+    getStroke(inputPoints as number[][], options),
+  );
+}
+
+function _legacy_getFreeDrawSvgPath(element: ExcalidrawFreeDrawElement) {
+  // If input points are empty (should they ever be?) return a dot
+  const inputPoints = element.simulatePressure
+    ? element.points
+    : element.points.length
+    ? element.points.map(([x, y], i) => [x, y, element.pressures[i]])
+    : [[0, 0, 0.5]];
+
+  // Consider changing the options for simulated pressure vs real pressure
+  const options: StrokeOptions = {
+    simulatePressure: element.simulatePressure,
+    size: element.strokeWidth * 4.25,
+    thinning: 0.6,
+    smoothing: 0.5,
+    streamline: 0.5,
+    easing: (t) => Math.sin((t * Math.PI) / 2), // https://easings.net/#easeOutSine
+    last: !!element.lastCommittedPoint, // LastCommittedPoint is added on pointerup
+  };
+
+  return _legacy_getSvgPathFromStroke(
+    getStroke(inputPoints as number[][], options),
+  );
+}
+
+const med = (A: number[], B: number[]) => {
+  return [(A[0] + B[0]) / 2, (A[1] + B[1]) / 2];
+};
+
+// Trim SVG path data so number are each two decimal points. This
+// improves SVG exports, and prevents rendering errors on points
+// with long decimals.
+const TO_FIXED_PRECISION = /(\s?[A-Z]?,?-?[0-9]*\.[0-9]{0,2})(([0-9]|e|-)*)/g;
+
+const _legacy_getSvgPathFromStroke = (points: number[][]): string => {
+  if (!points.length) {
+    return "";
+  }
+
+  const max = points.length - 1;
+
+  return points
+    .reduce(
+      (acc, point, i, arr) => {
+        if (i === max) {
+          acc.push(point, med(point, arr[0]), "L", arr[0], "Z");
+        } else {
+          acc.push(point, med(point, arr[i + 1]));
+        }
+        return acc;
+      },
+      ["M", points[0], "Q"],
+    )
+    .join(" ")
+    .replace(TO_FIXED_PRECISION, "$1");
+};

packages/element/src/index.ts

@@ -94,6 +94,7 @@ export * from "./embeddable";
 export * from "./flowchart";
 export * from "./fractionalIndex";
 export * from "./frame";
+export * from "./freedraw";
 export * from "./groups";
 export * from "./heading";
 export * from "./image";

packages/element/src/newElement.ts

@@ -445,6 +445,7 @@ export const newFreeDrawElement = (
     points?: ExcalidrawFreeDrawElement["points"];
     simulatePressure: boolean;
     pressures?: ExcalidrawFreeDrawElement["pressures"];
+    strokeOptions?: ExcalidrawFreeDrawElement["freedrawOptions"];
   } & ElementConstructorOpts,
 ): NonDeleted<ExcalidrawFreeDrawElement> => {
   return {
@@ -453,6 +454,11 @@ export const newFreeDrawElement = (
     pressures: opts.pressures || [],
     simulatePressure: opts.simulatePressure,
     lastCommittedPoint: null,
+    freedrawOptions: opts.strokeOptions || {
+      fixedStrokeWidth: true,
+      streamline: 0.25,
+      simplify: 0.1,
+    },
   };
 };
 

packages/element/src/renderElement.ts

@@ -1,5 +1,5 @@
 import rough from "roughjs/bin/rough";
-import { getStroke } from "perfect-freehand";
+import { getStroke, StrokeOptions } from "perfect-freehand";
 
 import {
   type GlobalPoint,
@@ -66,6 +66,8 @@ import { getCornerRadius } from "./utils";
 
 import { ShapeCache } from "./shape";
 
+import { getFreeDrawSvgPath } from "./freedraw";
+
 import type {
   ExcalidrawElement,
   ExcalidrawTextElement,
@@ -78,7 +80,6 @@ import type {
   ElementsMap,
 } from "./types";
 
-import type { StrokeOptions } from "perfect-freehand";
 import type { RoughCanvas } from "roughjs/bin/canvas";
 
 // using a stronger invert (100% vs our regular 93%) and saturate
@@ -1046,10 +1047,6 @@ export function getFreeDrawPath2D(element: ExcalidrawFreeDrawElement) {
   return pathsCache.get(element);
 }
 
-export function getFreeDrawSvgPath(element: ExcalidrawFreeDrawElement) {
-  return getSvgPathFromStroke(getFreedrawOutlinePoints(element));
-}
-
 export function getFreedrawOutlineAsSegments(
   element: ExcalidrawFreeDrawElement,
   points: readonly [number, number][],
@@ -1126,35 +1123,3 @@ export function getFreedrawOutlinePoints(element: ExcalidrawFreeDrawElement) {
 
   return getStroke(inputPoints as number[][], options) as [number, number][];
 }
-
-function med(A: number[], B: number[]) {
-  return [(A[0] + B[0]) / 2, (A[1] + B[1]) / 2];
-}
-
-// Trim SVG path data so number are each two decimal points. This
-// improves SVG exports, and prevents rendering errors on points
-// with long decimals.
-const TO_FIXED_PRECISION = /(\s?[A-Z]?,?-?[0-9]*\.[0-9]{0,2})(([0-9]|e|-)*)/g;
-
-function getSvgPathFromStroke(points: number[][]): string {
-  if (!points.length) {
-    return "";
-  }
-
-  const max = points.length - 1;
-
-  return points
-    .reduce(
-      (acc, point, i, arr) => {
-        if (i === max) {
-          acc.push(point, med(point, arr[0]), "L", arr[0], "Z");
-        } else {
-          acc.push(point, med(point, arr[i + 1]));
-        }
-        return acc;
-      },
-      ["M", points[0], "Q"],
-    )
-    .join(" ")
-    .replace(TO_FIXED_PRECISION, "$1");
-}

packages/element/src/shape.ts

@@ -21,6 +21,7 @@ import {
   assertNever,
   COLOR_PALETTE,
   LINE_POLYGON_POINT_MERGE_DISTANCE,
+  STROKE_WIDTH,
 } from "@excalidraw/common";
 
 import { RoughGenerator } from "roughjs/bin/generator";
@@ -202,7 +203,7 @@ export const generateRoughOptions = (
     // hachureGap because if not specified, roughjs uses strokeWidth to
     // calculate them (and we don't want the fills to be modified)
     fillWeight: element.strokeWidth / 2,
-    hachureGap: element.strokeWidth * 4,
+    hachureGap: Math.min(element.strokeWidth, STROKE_WIDTH.bold) * 4,
     roughness: adjustRoughness(element),
     stroke: element.strokeColor,
     preserveVertices:
@@ -806,15 +807,21 @@ const generateElementShape = (
       generateFreeDrawShape(element);
 
       if (isPathALoop(element.points)) {
-        // generate rough polygon to fill freedraw shape
-        const simplifiedPoints = simplify(
-          element.points as Mutable<LocalPoint[]>,
-          0.75,
-        );
-        shape = generator.curve(simplifiedPoints as [number, number][], {
-          ...generateRoughOptions(element),
-          stroke: "none",
-        });
+        const points =
+          element.freedrawOptions === null
+            ? simplify(element.points as LocalPoint[], 0.75)
+            : simplify(element.points as LocalPoint[], 1.5);
+
+        shape =
+          element.freedrawOptions === null
+            ? generator.curve(points, {
+                ...generateRoughOptions(element),
+                stroke: "none",
+              })
+            : generator.polygon(points, {
+                ...generateRoughOptions(element),
+                stroke: "none",
+              });
       } else {
         shape = null;
       }

packages/element/src/types.ts

@@ -380,6 +380,11 @@ export type ExcalidrawFreeDrawElement = _ExcalidrawElementBase &
     pressures: readonly number[];
     simulatePressure: boolean;
     lastCommittedPoint: LocalPoint | null;
+    freedrawOptions: {
+      streamline?: number;
+      simplify?: number;
+      fixedStrokeWidth?: boolean;
+    } | null;
   }>;
 
 export type FileId = string & { _brand: "FileId" };