[Bf-blender-cvs] [e2a18af69dc] greasepencil-object: Smooth new points while drawing

[Antonio Vazquez]

Commit: e2a18af69dcc9f48ca9a2bc1eca87abe91e851d4
Author: Antonio Vazquez
Date:   Mon Nov 6 16:55:50 2017 +0100
Branches: greasepencil-object
https://developer.blender.org/rBe2a18af69dcc9f48ca9a2bc1eca87abe91e851d4

Smooth new points while drawing

A new smooth algorithm is used for each new buffer point using the last two points to calculate the estimated position and average this point with the current mouse position.

This smooth reduce the jitter of the stroke and allows to use lower post smooth values to reduce stroke change after finish stroke.

Now the factor is hardcoded, but after some more testing maybe we need add a parameter by brush.

===================================================================

M	source/blender/editors/gpencil/gpencil_paint.c

===================================================================

diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index 48766f8846b..1b1452babef 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -469,6 +469,57 @@ static void gp_brush_angle(bGPdata *gpd, bGPDbrush *brush, tGPspoint *pt, const
 
 }
 
+static void copy_v2int_v2float(int r[2], const float a[2])
+{
+	r[0] = (int)a[0];
+	r[1] = (int)a[1];
+}
+
+static void copy_v2float_v2int(float r[2], const int a[2])
+{
+	r[0] = (float)a[0];
+	r[1] = (float)a[1];
+}
+
+/**
+* Apply smooth to last point of buffer
+* \param gpd              Current gp datablock
+* \param inf              Amount of smoothing to apply
+*/
+static bool gp_smooth_buffer_point(bGPdata *gpd, float inf)
+{
+	tGPspoint *pt, *pta, *ptb;
+	float fpt[2], fpta[2], fptb[2];
+	float sco[2] = { 0.0f };
+
+	/* Do nothing if not enough points to smooth out */
+	if (gpd->sbuffer_size < 3) {
+		return false;
+	}
+
+	int i = gpd->sbuffer_size - 1;
+
+	/* points used as reference */
+	pta = (tGPspoint *)gpd->sbuffer + i - 2;
+	ptb = (tGPspoint *)gpd->sbuffer + i - 1;
+
+	/* current point */
+	pt = (tGPspoint *)gpd->sbuffer + i;
+
+	/* compute estimated position following last two points vector */
+	copy_v2float_v2int(fpta, &pta->x);
+	copy_v2float_v2int(fptb, &ptb->x);
+	copy_v2float_v2int(fpt, &pt->x);
+	float lambda = closest_to_line_v2(sco, fpt, fpta, fptb);
+	if (lambda > 0.0f) {
+		/* blend between original and optimal smoothed coordinate */
+		interp_v2_v2v2(fpt, fpt, sco, inf);
+		copy_v2int_v2float(&pt->x, fpt);
+	}
+	return true;
+}
+
+
 /* add current stroke-point to buffer (returns whether point was successfully added) */
 static short gp_stroke_addpoint(
         tGPsdata *p, const int mval[2], float pressure, double curtime)
@@ -531,6 +582,7 @@ static short gp_stroke_addpoint(
 		else {
 			pt->pressure = 1.0f;
 		}
+
 		/* Apply jitter to position */
 		if (brush->draw_jitter > 0.0f) {
 			int r_mval[2];
@@ -586,7 +638,11 @@ static short gp_stroke_addpoint(
 		
 		/* increment counters */
 		gpd->sbuffer_size++;
-		
+
+		/* apply dynamic smooth to point */
+		/* TODO: now the influence is harcoded to 0.6, maybe need a parameter by brush or session? */
+		gp_smooth_buffer_point(gpd, 0.6f);
+
 		/* check if another operation can still occur */
 		if (gpd->sbuffer_size == GP_STROKE_BUFFER_MAX)
 			return GP_STROKEADD_FULL;