blender-archive/source/blender/editors/curve/editcurve_paint.c

/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/editors/curve/editcurve_paint.c
 *  \ingroup edcurve
 */

#include "DNA_object_types.h"
#include "DNA_scene_types.h"

#include "MEM_guardedalloc.h"

#include "BLI_blenlib.h"
#include "BLI_math.h"
#include "BLI_mempool.h"

#include "BKE_context.h"
#include "BKE_curve.h"
#include "BKE_depsgraph.h"
#include "BKE_fcurve.h"
#include "BKE_report.h"

#include "WM_api.h"
#include "WM_types.h"

#include "ED_space_api.h"
#include "ED_screen.h"
#include "ED_view3d.h"
#include "ED_curve.h"

#include "BIF_gl.h"
#include "BIF_glutil.h"

#include "curve_intern.h"

#include "UI_resources.h"

#include "RNA_access.h"
#include "RNA_define.h"

#define USE_SPLINE_FIT

#ifdef USE_SPLINE_FIT
#include "curve_fit_nd.h"
#endif

/* Distance between input samples */
#define STROKE_SAMPLE_DIST_MIN_PX 3
#define STROKE_SAMPLE_DIST_MAX_PX 6


/* -------------------------------------------------------------------- */

/** \name Depth Utilities
 * \{ */


static float depth_read_zbuf(const ViewContext *vc, int x, int y)
{
	ViewDepths *vd = vc->rv3d->depths;

	if (vd && vd->depths && x > 0 && y > 0 && x < vd->w && y < vd->h)
		return vd->depths[y * vd->w + x];
	else
		return -1.0f;
}

static bool depth_unproject(
        const ARegion *ar, const bglMats *mats,
        const int mval[2], const double depth,
        float r_location_world[3])
{
	double p[3];
	if (gluUnProject(
	        (double)ar->winrct.xmin + mval[0] + 0.5,
	        (double)ar->winrct.ymin + mval[1] + 0.5,
	        depth, mats->modelview, mats->projection, (const GLint *)mats->viewport,
	        &p[0], &p[1], &p[2]))
	{
		copy_v3fl_v3db(r_location_world, p);
		return true;
	}
	return false;
}

static bool depth_read_normal(
        const ViewContext *vc, const bglMats *mats, const int mval[2],
        float r_normal[3])
{
	/* pixels surrounding */
	bool  depths_valid[9] = {false};
	float coords[9][3] = {{0}};

	ARegion *ar = vc->ar;
	const ViewDepths *depths = vc->rv3d->depths;

	for (int x = 0, i = 0; x < 2; x++) {
		for (int y = 0; y < 2; y++) {
			const int mval_ofs[2] = {mval[0] + (x - 1), mval[1] + (y - 1)};

			const double depth = (double)depth_read_zbuf(vc, mval_ofs[0], mval_ofs[1]);
			if ((depth > depths->depth_range[0]) && (depth < depths->depth_range[1])) {
				if (depth_unproject(ar, mats, mval_ofs, depth, coords[i])) {
					depths_valid[i] = true;
				}
			}
			i++;
		}
	}

	const int edges[2][6][2] = {
	    /* x edges */
	    {{0, 1}, {1, 2},
	     {3, 4}, {4, 5},
	     {6, 7}, {7, 8}},
	    /* y edges */
	    {{0, 3}, {3, 6},
	     {1, 4}, {4, 7},
	     {2, 5}, {5, 8}},
	};

	float cross[2][3] = {{0.0f}};

	for (int i = 0; i < 6; i++) {
		for (int axis = 0; axis < 2; axis++) {
			if (depths_valid[edges[axis][i][0]] && depths_valid[edges[axis][i][1]]) {
				float delta[3];
				sub_v3_v3v3(delta, coords[edges[axis][i][0]], coords[edges[axis][i][1]]);
				add_v3_v3(cross[axis], delta);
			}
		}
	}

	cross_v3_v3v3(r_normal, cross[0], cross[1]);

	if (normalize_v3(r_normal) != 0.0f) {
		return true;
	}
	else {
		return false;
	}
}

/** \} */


/* -------------------------------------------------------------------- */

/** \name StrokeElem / #RNA_OperatorStrokeElement Conversion Functions
 * \{ */

struct StrokeElem {
	float mval[2];
	float location_world[3];
	float location_local[3];

	/* surface normal, may be zero'd */
	float normal_world[3];
	float normal_local[3];

	float pressure;
};

struct CurveDrawData {
	short init_event_type;
	short curve_type;

	/* projecting 2D into 3D space */
	struct {
		/* use a plane or project to the surface */
		bool use_plane;
		float    plane[4];

		/* use 'rv3d->depths', note that this will become 'damaged' while drawing, but thats OK. */
		bool use_depth;

		/* offset projection by this value */
		bool use_offset;
		float    offset[3];  /* worldspace */
		float    surface_offset;
		bool     use_surface_offset_absolute;
	} project;

	/* cursor sampling */
	struct {
		/* use substeps, needed for nicely interpolating depth */
		bool use_substeps;
	} sample;

	struct {
		float min, max, range;
	} radius;

	struct {
		float mouse[2];
		/* used incase we can't calculate the depth */
		float location_world[3];

		float location_world_valid[3];

		const struct StrokeElem *selem;
	} prev;

	ViewContext vc;
	bglMats mats;
	enum {
		CURVE_DRAW_IDLE = 0,
		CURVE_DRAW_PAINTING = 1,
	} state;

	/* StrokeElem */
	BLI_mempool *stroke_elem_pool;

	void *draw_handle_view;
};

static float stroke_elem_radius_from_pressure(const struct CurveDrawData *cdd, const float pressure)
{
	const Curve *cu = cdd->vc.obedit->data;
	return ((pressure * cdd->radius.range) + cdd->radius.min) * cu->ext2;
}

static float stroke_elem_radius(const struct CurveDrawData *cdd, const struct StrokeElem *selem)
{
	return stroke_elem_radius_from_pressure(cdd, selem->pressure);
}

static void stroke_elem_pressure_set(const struct CurveDrawData *cdd, struct StrokeElem *selem, float pressure)
{
	if ((cdd->project.surface_offset != 0.0f) &&
	    !cdd->project.use_surface_offset_absolute &&
	    !is_zero_v3(selem->normal_local))
	{
		const float adjust = stroke_elem_radius_from_pressure(cdd, pressure) -
		                     stroke_elem_radius_from_pressure(cdd, selem->pressure);
		madd_v3_v3fl(selem->location_local, selem->normal_local, adjust);
		mul_v3_m4v3(selem->location_world, cdd->vc.obedit->obmat, selem->location_local);
	}
	selem->pressure = pressure;
}

static void stroke_elem_interp(
        struct StrokeElem *selem_out,
        const struct StrokeElem *selem_a,  const struct StrokeElem *selem_b, float t)
{
	interp_v2_v2v2(selem_out->mval, selem_a->mval, selem_b->mval, t);
	interp_v3_v3v3(selem_out->location_world, selem_a->location_world, selem_b->location_world, t);
	interp_v3_v3v3(selem_out->location_local, selem_a->location_local, selem_b->location_local, t);
	selem_out->pressure = interpf(selem_a->pressure, selem_b->pressure, t);
}


/**
 * Sets the depth from #StrokeElem.mval
 */
static bool stroke_elem_project(
        const struct CurveDrawData *cdd,
        const int mval_i[2], const float mval_fl[2],
        float surface_offset, const float radius,
        float r_location_world[3], float r_normal_world[3])
{
	View3D *v3d = cdd->vc.v3d;
	ARegion *ar = cdd->vc.ar;
	RegionView3D *rv3d = cdd->vc.rv3d;

	bool is_location_world_set = false;

	/* project to 'location_world' */
	if (cdd->project.use_plane) {
		/* get the view vector to 'location' */
		float ray_origin[3], ray_direction[3];
		ED_view3d_win_to_ray(cdd->vc.ar, v3d, mval_fl, ray_origin, ray_direction, false);

		float lambda;
		if (isect_ray_plane_v3(ray_origin, ray_direction, cdd->project.plane, &lambda, true)) {
			madd_v3_v3v3fl(r_location_world, ray_origin, ray_direction, lambda);
			if (r_normal_world) {
				zero_v3(r_normal_world);
			}
			is_location_world_set = true;
		}
	}
	else {
		const ViewDepths *depths = rv3d->depths;
		if (depths &&
		    ((unsigned int)mval_i[0] < depths->w) &&
		    ((unsigned int)mval_i[1] < depths->h))
		{
			const double depth = (double)depth_read_zbuf(&cdd->vc, mval_i[0], mval_i[1]);
			if ((depth > depths->depth_range[0]) && (depth < depths->depth_range[1])) {
				if (depth_unproject(ar, &cdd->mats, mval_i, depth, r_location_world)) {
					is_location_world_set = true;
					if (r_normal_world) {
						zero_v3(r_normal_world);
					}

					if (surface_offset != 0.0f) {
						const float offset = cdd->project.use_surface_offset_absolute ? 1.0f : radius;
						float normal[3];
						if (depth_read_normal(&cdd->vc, &cdd->mats, mval_i, normal)) {
							madd_v3_v3fl(r_location_world, normal, offset * surface_offset);
							if (r_normal_world) {
								copy_v3_v3(r_normal_world, normal);
							}
						}
					}
				}
			}
		}
	}

	if (is_location_world_set) {
		if (cdd->project.use_offset) {
			add_v3_v3(r_location_world, cdd->project.offset);
		}
	}

	return is_location_world_set;
}

static bool stroke_elem_project_fallback(
        const struct CurveDrawData *cdd,
        const int mval_i[2], const float mval_fl[2],
        const float surface_offset, const float radius,
        const float location_fallback_depth[3],
        float r_location_world[3], float r_location_local[3],
        float r_normal_world[3], float r_normal_local[3])
{
	bool is_depth_found = stroke_elem_project(
	        cdd, mval_i, mval_fl,
	        surface_offset, radius,
	        r_location_world, r_normal_world);
	if (is_depth_found == false) {
		ED_view3d_win_to_3d(cdd->vc.ar, location_fallback_depth, mval_fl, r_location_world);
		zero_v3(r_normal_local);
	}
	mul_v3_m4v3(r_location_local, cdd->vc.obedit->imat, r_location_world);

	if (!is_zero_v3(r_normal_world)) {
		copy_v3_v3(r_normal_local, r_normal_world);
		mul_transposed_mat3_m4_v3(cdd->vc.obedit->obmat, r_normal_local);
		normalize_v3(r_normal_local);
	}
	else {
		zero_v3(r_normal_local);
	}

	return is_depth_found;
}

/**
 * \note #StrokeElem.mval & #StrokeElem.pressure must be set first.
 */
static bool stroke_elem_project_fallback_elem(
        const struct CurveDrawData *cdd,
        const float location_fallback_depth[3],
        struct StrokeElem *selem)
{
	const int mval_i[2] = {UNPACK2(selem->mval)};
	const float radius = stroke_elem_radius(cdd, selem);
	return stroke_elem_project_fallback(
	        cdd, mval_i, selem->mval,
	        cdd->project.surface_offset, radius,
	        location_fallback_depth,
	        selem->location_world, selem->location_local,
	        selem->normal_world, selem->normal_local);
}

/** \} */


/* -------------------------------------------------------------------- */

/** \name Operator/Stroke Conversion
 * \{ */

static void curve_draw_stroke_to_operator_elem(
        wmOperator *op, const struct StrokeElem *selem)
{
	PointerRNA itemptr;
	RNA_collection_add(op->ptr, "stroke", &itemptr);

	RNA_float_set_array(&itemptr, "mouse", selem->mval);
	RNA_float_set_array(&itemptr, "location", selem->location_world);
	RNA_float_set(&itemptr, "pressure", selem->pressure);
}

static void curve_draw_stroke_from_operator_elem(
        wmOperator *op, PointerRNA *itemptr)
{
	struct CurveDrawData *cdd = op->customdata;

	struct StrokeElem *selem = BLI_mempool_calloc(cdd->stroke_elem_pool);

	RNA_float_get_array(itemptr, "mouse", selem->mval);
	RNA_float_get_array(itemptr, "location", selem->location_world);
	mul_v3_m4v3(selem->location_local, cdd->vc.obedit->imat, selem->location_world);
	selem->pressure = RNA_float_get(itemptr, "pressure");
}

static void curve_draw_stroke_to_operator(wmOperator *op)
{
	struct CurveDrawData *cdd = op->customdata;

	BLI_mempool_iter iter;
	const struct StrokeElem *selem;

	BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
	for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
		curve_draw_stroke_to_operator_elem(op, selem);
	}
}

static void curve_draw_stroke_from_operator(wmOperator *op)
{
	RNA_BEGIN (op->ptr, itemptr, "stroke")
	{
		curve_draw_stroke_from_operator_elem(op, &itemptr);
	}
	RNA_END;
}

/** \} */


/* -------------------------------------------------------------------- */

/** \name Operator Callbacks & Helpers
 * \{ */

static void curve_draw_stroke_3d(const struct bContext *UNUSED(C), ARegion *UNUSED(ar), void *arg)
{
	wmOperator *op = arg;
	struct CurveDrawData *cdd = op->customdata;

	const int stroke_len = BLI_mempool_count(cdd->stroke_elem_pool);

	if (stroke_len == 0) {
		return;
	}

	View3D *v3d = cdd->vc.v3d;
	Object *obedit = cdd->vc.obedit;
	Curve *cu = obedit->data;

	UI_ThemeColor(TH_WIRE);

	if (cu->ext2 > 0.0f) {
		GLUquadricObj *qobj = gluNewQuadric();

		gluQuadricDrawStyle(qobj, GLU_FILL);

		BLI_mempool_iter iter;
		const struct StrokeElem *selem;

		const float  location_zero[3] = {0};
		const float *location_prev = location_zero;

		/* scale to edit-mode space */
		glPushMatrix();
		glMultMatrixf(obedit->obmat);

		BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
		for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
			glTranslatef(
			        selem->location_local[0] - location_prev[0],
			        selem->location_local[1] - location_prev[1],
			        selem->location_local[2] - location_prev[2]);
			location_prev = selem->location_local;
			const float radius = stroke_elem_radius(cdd, selem);
			gluSphere(qobj, radius , 12, 8);

			location_prev = selem->location_local;
		}

		glPopMatrix();

		gluDeleteQuadric(qobj);
	}

	if (stroke_len > 1) {
		float (*coord_array)[3] = MEM_mallocN(sizeof(*coord_array) * stroke_len, __func__);

		{
			BLI_mempool_iter iter;
			const struct StrokeElem *selem;
			int i;
			BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
			for (selem = BLI_mempool_iterstep(&iter), i = 0; selem; selem = BLI_mempool_iterstep(&iter), i++) {
				copy_v3_v3(coord_array[i], selem->location_world);
			}
		}

		{
			glEnable(GL_BLEND);
			glEnable(GL_LINE_SMOOTH);

			glEnableClientState(GL_VERTEX_ARRAY);
			glVertexPointer(3, GL_FLOAT, 0, coord_array);

			cpack(0x0);
			glLineWidth(3.0f);
			glDrawArrays(GL_LINE_STRIP, 0, stroke_len);

			if (v3d->zbuf)
				glDisable(GL_DEPTH_TEST);

			cpack(0xffffffff);
			glLineWidth(1.0f);
			glDrawArrays(GL_LINE_STRIP, 0, stroke_len);

			if (v3d->zbuf)
				glEnable(GL_DEPTH_TEST);

			glDisableClientState(GL_VERTEX_ARRAY);

			glDisable(GL_BLEND);
			glDisable(GL_LINE_SMOOTH);
		}

		MEM_freeN(coord_array);
	}
}

static void curve_draw_event_add(wmOperator *op, const wmEvent *event)
{
	struct CurveDrawData *cdd = op->customdata;
	Object *obedit = cdd->vc.obedit;

	invert_m4_m4(obedit->imat, obedit->obmat);

	struct StrokeElem *selem = BLI_mempool_calloc(cdd->stroke_elem_pool);

	ARRAY_SET_ITEMS(selem->mval, event->mval[0], event->mval[1]);

	/* handle pressure sensitivity (which is supplied by tablets) */
	if (event->tablet_data) {
		const wmTabletData *wmtab = event->tablet_data;
		selem->pressure = wmtab->Pressure;
	}
	else {
		selem->pressure = 1.0f;
	}

	bool is_depth_found = stroke_elem_project_fallback_elem(
	        cdd, cdd->prev.location_world_valid, selem);

	if (is_depth_found) {
		/* use the depth if a fallback wasn't used */
		copy_v3_v3(cdd->prev.location_world_valid, selem->location_world);
	}
	copy_v3_v3(cdd->prev.location_world, selem->location_world);

	float len_sq = len_squared_v2v2(cdd->prev.mouse, selem->mval);
	copy_v2_v2(cdd->prev.mouse, selem->mval);

	if (cdd->sample.use_substeps && cdd->prev.selem) {
		const struct StrokeElem selem_target = *selem;
		struct StrokeElem *selem_new_last = selem;
		if (len_sq >= SQUARE(STROKE_SAMPLE_DIST_MAX_PX)) {
			int n = (int)ceil(sqrt((double)len_sq)) / STROKE_SAMPLE_DIST_MAX_PX ;

			for (int i = 1; i < n; i++) {
				struct StrokeElem *selem_new = selem_new_last;
				stroke_elem_interp(selem_new, cdd->prev.selem, &selem_target, (float)i / n);

				const bool is_depth_found_substep = stroke_elem_project_fallback_elem(
				        cdd, cdd->prev.location_world_valid, selem_new);
				if (is_depth_found == false) {
					if (is_depth_found_substep) {
						copy_v3_v3(cdd->prev.location_world_valid, selem_new->location_world);
					}
				}

				selem_new_last = BLI_mempool_calloc(cdd->stroke_elem_pool);
			}
		}
		selem = selem_new_last;
		*selem_new_last = selem_target;
	}

	cdd->prev.selem = selem;

	ED_region_tag_redraw(cdd->vc.ar);
}

static void curve_draw_event_add_first(wmOperator *op, const wmEvent *event)
{
	struct CurveDrawData *cdd = op->customdata;
	const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;

	/* add first point */
	curve_draw_event_add(op, event);

	if ((cps->depth_mode == CURVE_PAINT_PROJECT_SURFACE) && cdd->project.use_depth &&
	    (cps->flag & CURVE_PAINT_FLAG_DEPTH_STROKE_ENDPOINTS))
	{
		RegionView3D *rv3d = cdd->vc.rv3d;

		cdd->project.use_depth = false;
		cdd->project.use_plane = true;

		float normal[3] = {0.0f};
		if (ELEM(cps->surface_plane,
		         CURVE_PAINT_SURFACE_PLANE_NORMAL_VIEW,
		         CURVE_PAINT_SURFACE_PLANE_NORMAL_SURFACE))
		{
			if (depth_read_normal(&cdd->vc, &cdd->mats, event->mval, normal)) {
				if (cps->surface_plane == CURVE_PAINT_SURFACE_PLANE_NORMAL_VIEW) {
					float cross_a[3], cross_b[3];
					cross_v3_v3v3(cross_a, rv3d->viewinv[2], normal);
					cross_v3_v3v3(cross_b, normal, cross_a);
					copy_v3_v3(normal, cross_b);
				}
			}
		}

		/* CURVE_PAINT_SURFACE_PLANE_VIEW or fallback */
		if (is_zero_v3(normal)) {
			copy_v3_v3(normal, rv3d->viewinv[2]);
		}

		normalize_v3_v3(cdd->project.plane, normal);
		cdd->project.plane[3] = -dot_v3v3(cdd->project.plane, cdd->prev.location_world_valid);

		/* Special case for when we only have offset applied on the first-hit,
		 * the remaining stroke must be offset too. */
		if (cdd->project.surface_offset != 0.0f) {
			const float mval_fl[2] = {UNPACK2(event->mval)};

			float location_no_offset[3];

			if (stroke_elem_project(
			        cdd, event->mval, mval_fl, 0.0f, 0.0f,
			        location_no_offset, NULL))
			{
				sub_v3_v3v3(cdd->project.offset, cdd->prev.location_world_valid, location_no_offset);
				if (!is_zero_v3(cdd->project.offset)) {
					cdd->project.use_offset = true;
				}
			}
		}
		/* end special case */

	}

	cdd->init_event_type = event->type;
	cdd->state = CURVE_DRAW_PAINTING;
}

static bool curve_draw_init(bContext *C, wmOperator *op, bool is_invoke)
{
	BLI_assert(op->customdata == NULL);

	struct CurveDrawData *cdd = MEM_callocN(sizeof(*cdd), __func__);

	if (is_invoke) {
		view3d_set_viewcontext(C, &cdd->vc);
		if (ELEM(NULL, cdd->vc.ar, cdd->vc.rv3d, cdd->vc.v3d, cdd->vc.win, cdd->vc.scene)) {
			MEM_freeN(cdd);
			BKE_report(op->reports, RPT_ERROR, "Unable to access 3D viewport");
			return false;
		}
	}
	else {
		cdd->vc.scene = CTX_data_scene(C);
		cdd->vc.obedit = CTX_data_edit_object(C);
	}

	op->customdata = cdd;

	const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;

	cdd->curve_type = cps->curve_type;

	cdd->radius.min = cps->radius_min;
	cdd->radius.max = cps->radius_max;
	cdd->radius.range = cps->radius_max - cps->radius_min;
	cdd->project.surface_offset = cps->surface_offset;
	cdd->project.use_surface_offset_absolute = (cps->flag & CURVE_PAINT_FLAG_DEPTH_STROKE_OFFSET_ABS) != 0;

	cdd->stroke_elem_pool = BLI_mempool_create(
	        sizeof(struct StrokeElem), 0, 512, BLI_MEMPOOL_ALLOW_ITER);

	return true;
}


static void curve_draw_exit(wmOperator *op)
{
	struct CurveDrawData *cdd = op->customdata;
	if (cdd) {
		if (cdd->draw_handle_view) {
			ED_region_draw_cb_exit(cdd->vc.ar->type, cdd->draw_handle_view);
			WM_cursor_modal_restore(cdd->vc.win);
		}

		if (cdd->stroke_elem_pool) {
			BLI_mempool_destroy(cdd->stroke_elem_pool);
		}

		MEM_freeN(cdd);
		op->customdata = NULL;
	}
}

/**
 * Initialize values before calling 'exec' (when running interactively).
 */
static void curve_draw_exec_precalc(wmOperator *op)
{
	struct CurveDrawData *cdd = op->customdata;
	const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;
	PropertyRNA *prop;

	prop = RNA_struct_find_property(op->ptr, "corner_angle");
	if (!RNA_property_is_set(op->ptr, prop)) {
		const float corner_angle = (cps->flag & CURVE_PAINT_FLAG_CORNERS_DETECT) ? cps->corner_angle : (float)M_PI;
		RNA_property_float_set(op->ptr, prop, corner_angle);
	}

	prop = RNA_struct_find_property(op->ptr, "error_threshold");
	if (!RNA_property_is_set(op->ptr, prop)) {

		/* error isnt set so we'll have to calculate it from the pixel values */
		BLI_mempool_iter iter;
		const struct StrokeElem *selem, *selem_prev;

		float len_3d = 0.0f, len_2d = 0.0f;
		float scale_px;  /* pixel to local space scale */

		int i = 0;
		BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
		selem_prev = BLI_mempool_iterstep(&iter);
		for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter), i++) {
			len_3d += len_v3v3(selem->location_local, selem_prev->location_local);
			len_2d += len_v2v2(selem->mval, selem_prev->mval);
			selem_prev = selem;
		}
		scale_px = ((len_3d > 0.0f) && (len_2d > 0.0f)) ?  (len_3d / len_2d) : 0.0f;
		float error_threshold = (cps->error_threshold * U.pixelsize) * scale_px;
		RNA_property_float_set(op->ptr, prop, error_threshold);
	}

	if ((cps->radius_taper_start != 0.0f) ||
	    (cps->radius_taper_end   != 0.0f))
	{
		/* note, we could try to de-duplicate the length calculations above */
		const int stroke_len = BLI_mempool_count(cdd->stroke_elem_pool);

		BLI_mempool_iter iter;
		struct StrokeElem *selem, *selem_prev;

		float *lengths = MEM_mallocN(sizeof(float) * stroke_len, __func__);
		struct StrokeElem **selem_array = MEM_mallocN(sizeof(*selem_array) * stroke_len, __func__);
		lengths[0] = 0.0f;

		float len_3d = 0.0f;

		int i = 1;
		BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
		selem_prev = BLI_mempool_iterstep(&iter);
		selem_array[0] = selem_prev;
		for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter), i++) {
			const float len_3d_segment = len_v3v3(selem->location_local, selem_prev->location_local);
			len_3d += len_3d_segment;
			lengths[i] = len_3d;
			selem_array[i] = selem;
			selem_prev = selem;
		}

		if (cps->radius_taper_start != 0.0f) {
			const float len_taper_max = cps->radius_taper_start * len_3d;
			for (i = 0; i < stroke_len && lengths[i] < len_taper_max; i++) {
				const float pressure_new = selem_array[i]->pressure * (lengths[i] / len_taper_max);
				stroke_elem_pressure_set(cdd, selem_array[i], pressure_new);
			}
		}

		if (cps->radius_taper_end != 0.0f) {
			const float len_taper_max = cps->radius_taper_end * len_3d;
			const float len_taper_min = len_3d - len_taper_max;
			for (i = stroke_len - 1; i > 0 && lengths[i] > len_taper_min; i--) {
				const float pressure_new = selem_array[i]->pressure * ((len_3d - lengths[i]) / len_taper_max);
				stroke_elem_pressure_set(cdd, selem_array[i], pressure_new);
			}
		}

		MEM_freeN(lengths);
		MEM_freeN(selem_array);
	}
}

static int curve_draw_exec(bContext *C, wmOperator *op)
{
	if (op->customdata == NULL) {
		if (!curve_draw_init(C, op, false)) {
			return OPERATOR_CANCELLED;
		}
	}

	struct CurveDrawData *cdd = op->customdata;

	const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;
	Object *obedit = cdd->vc.scene->obedit;
	Curve *cu = obedit->data;
	ListBase *nurblist = object_editcurve_get(obedit);

	int stroke_len = BLI_mempool_count(cdd->stroke_elem_pool);

	const bool is_3d = (cu->flag & CU_3D) != 0;
	invert_m4_m4(obedit->imat, obedit->obmat);

	if (BLI_mempool_count(cdd->stroke_elem_pool) == 0) {
		curve_draw_stroke_from_operator(op);
		stroke_len = BLI_mempool_count(cdd->stroke_elem_pool);
	}

	ED_curve_deselect_all(cu->editnurb);

	const float radius_min = cps->radius_min;
	const float radius_max = cps->radius_max;
	const float radius_range = cps->radius_max - cps->radius_min;

	Nurb *nu = MEM_callocN(sizeof(Nurb), __func__);
	nu->pntsv = 1;
	nu->resolu = cu->resolu;
	nu->resolv = cu->resolv;
	nu->flag |= CU_SMOOTH;

	const bool use_pressure_radius =
	        (cps->flag & CURVE_PAINT_FLAG_PRESSURE_RADIUS) ||
	        ((cps->radius_taper_start != 0.0f) ||
	         (cps->radius_taper_end   != 0.0f));

	if (cdd->curve_type == CU_BEZIER) {
		nu->type = CU_BEZIER;

#ifdef USE_SPLINE_FIT

		/* Allow to interpolate multiple channels */
		int dims = 3;
		struct {
			int radius;
		} coords_indices;
		coords_indices.radius = use_pressure_radius ? dims++ : -1;

		float *coords = MEM_mallocN(sizeof(*coords) * stroke_len * dims, __func__);

		float       *cubic_spline = NULL;
		unsigned int cubic_spline_len = 0;

		/* error in object local space */
		const float error_threshold = RNA_float_get(op->ptr, "error_threshold");
		const float corner_angle = RNA_float_get(op->ptr, "corner_angle");

		{
			BLI_mempool_iter iter;
			const struct StrokeElem *selem;
			float *co = coords;

			BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
			for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter), co += dims) {
				copy_v3_v3(co, selem->location_local);
				if (coords_indices.radius != -1) {
					co[coords_indices.radius] = selem->pressure;
				}

				/* remove doubles */
				if ((co != coords) && UNLIKELY(memcmp(co, co - dims, sizeof(float) * dims) == 0)) {
					co -= dims;
					stroke_len--;
				}
			}
		}

		unsigned int *corners = NULL;
		unsigned int  corners_len = 0;

		if (corner_angle < (float)M_PI) {
			/* this could be configurable... */
			const float corner_radius_min = error_threshold / 8;
			const float corner_radius_max = error_threshold * 2;
			const unsigned int samples_max = 16;

			curve_fit_corners_detect_fl(
			        (const float *)coords, stroke_len, dims,
			        corner_radius_min, corner_radius_max,
			        samples_max, corner_angle,
			        &corners, &corners_len);
		}

		unsigned int *corners_index = NULL;
		unsigned int  corners_index_len = 0;

		const int result = curve_fit_cubic_to_points_fl(
		        coords, stroke_len, dims, error_threshold,
		        corners, corners_len,
		        &cubic_spline, &cubic_spline_len,
		        NULL,
		        &corners_index, &corners_index_len);

		MEM_freeN(coords);
		if (corners) {
			free(corners);
		}

		if (result == 0) {
			nu->pntsu = cubic_spline_len;
			nu->bezt = MEM_callocN(sizeof(BezTriple) * nu->pntsu, __func__);

			float *co = cubic_spline;
			BezTriple *bezt = nu->bezt;
			for (int j = 0; j < cubic_spline_len; j++, bezt++, co += (dims * 3)) {
				const float *handle_l = co + (dims * 0);
				const float *pt       = co + (dims * 1);
				const float *handle_r = co + (dims * 2);

				copy_v3_v3(bezt->vec[0], handle_l);
				copy_v3_v3(bezt->vec[1], pt);
				copy_v3_v3(bezt->vec[2], handle_r);

				if (coords_indices.radius != -1) {
					bezt->radius = (pt[coords_indices.radius] * cdd->radius.range) + cdd->radius.min;
				}
				else {
					bezt->radius = radius_max;
				}

				bezt->h1 = bezt->h2 = HD_ALIGN;  /* will set to free in second pass */
				bezt->f1 = bezt->f2 = bezt->f3 = SELECT;
			}

			if (corners_index) {
				/* ignore the first and last */
				for (unsigned int i = 1; i < corners_index_len - 1; i++) {
					bezt = &nu->bezt[corners_index[i]];
					bezt->h1 = bezt->h2 = HD_FREE;
				}
			}
		}

		if (corners_index) {
			free(corners_index);
		}

		if (cubic_spline) {
			free(cubic_spline);
		}

#else
		nu->pntsu = stroke_len;
		nu->bezt = MEM_callocN(nu->pntsu * sizeof(BezTriple), __func__);

		BezTriple *bezt = nu->bezt;

		{
			BLI_mempool_iter iter;
			const struct StrokeElem *selem;

			BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
			for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
				copy_v3_v3(bezt->vec[1], selem->location_local);
				if (!is_3d) {
					bezt->vec[1][2] = 0.0f;
				}

				if (use_pressure_radius) {
					bezt->radius = selem->pressure;
				}
				else {
					bezt->radius = radius_max;
				}

				bezt->h1 = bezt->h2 = HD_AUTO;

				bezt->f1 |= SELECT;
				bezt->f2 |= SELECT;
				bezt->f3 |= SELECT;

				bezt++;
			}
		}
#endif

		BKE_nurb_handles_calc(nu);
	}
	else {  /* CU_POLY */
		BLI_mempool_iter iter;
		const struct StrokeElem *selem;

		nu->pntsu = stroke_len;
		nu->type = CU_POLY;
		nu->bp = MEM_callocN(nu->pntsu * sizeof(BPoint), __func__);

		BPoint *bp = nu->bp;

		BLI_mempool_iternew(cdd->stroke_elem_pool, &iter);
		for (selem = BLI_mempool_iterstep(&iter); selem; selem = BLI_mempool_iterstep(&iter)) {
			copy_v3_v3(bp->vec, selem->location_local);
			if (!is_3d) {
				bp->vec[2] = 0.0f;
			}

			if (use_pressure_radius) {
				bp->radius = (selem->pressure * radius_range) + radius_min;
			}
			else {
				bp->radius = cps->radius_max;
			}
			bp->f1 = SELECT;
			bp->vec[3] = 1.0f;

			bp++;
		}

		BKE_nurb_knot_calc_u(nu);
	}

	BLI_addtail(nurblist, nu);

	BKE_curve_nurb_active_set(cu, nu);
	cu->actvert = nu->pntsu - 1;

	WM_event_add_notifier(C, NC_GEOM | ND_DATA, obedit->data);
	DAG_id_tag_update(obedit->data, 0);

	curve_draw_exit(op);

	return OPERATOR_FINISHED;
}

static int curve_draw_invoke(bContext *C, wmOperator *op, const wmEvent *event)
{
	if (RNA_struct_property_is_set(op->ptr, "stroke")) {
		return curve_draw_exec(C, op);
	}

	if (!curve_draw_init(C, op, true)) {
		return OPERATOR_CANCELLED;
	}

	struct CurveDrawData *cdd = op->customdata;

	const CurvePaintSettings *cps = &cdd->vc.scene->toolsettings->curve_paint_settings;

	const bool is_modal = RNA_boolean_get(op->ptr, "wait_for_input");

	/* fallback (incase we can't find the depth on first test) */
	{
		const float mval_fl[2] = {UNPACK2(event->mval)};
		float center[3];
		negate_v3_v3(center, cdd->vc.rv3d->ofs);
		ED_view3d_win_to_3d(cdd->vc.ar, center, mval_fl, cdd->prev.location_world);
		copy_v3_v3(cdd->prev.location_world_valid, cdd->prev.location_world);
	}

	cdd->draw_handle_view = ED_region_draw_cb_activate(
	        cdd->vc.ar->type, curve_draw_stroke_3d, op, REGION_DRAW_POST_VIEW);
	WM_cursor_modal_set(cdd->vc.win, BC_PAINTBRUSHCURSOR);

	{
		View3D *v3d = cdd->vc.v3d;
		RegionView3D *rv3d = cdd->vc.rv3d;
		Object *obedit = cdd->vc.obedit;
		Curve *cu = obedit->data;

		const float *plane_no = NULL;
		const float *plane_co = NULL;

		if ((cu->flag & CU_3D) == 0) {
			/* 2D overrides other options */
			plane_co = obedit->obmat[3];
			plane_no = obedit->obmat[2];
			cdd->project.use_plane = true;
		}
		else {
			if ((cps->depth_mode == CURVE_PAINT_PROJECT_SURFACE) &&
			    (v3d->drawtype > OB_WIRE))
			{
				view3d_get_transformation(cdd->vc.ar, cdd->vc.rv3d, NULL, &cdd->mats);

				/* needed or else the draw matrix can be incorrect */
				view3d_operator_needs_opengl(C);

				ED_view3d_autodist_init(cdd->vc.scene, cdd->vc.ar, cdd->vc.v3d, 0);

				if (cdd->vc.rv3d->depths) {
					cdd->vc.rv3d->depths->damaged = true;
				}

				ED_view3d_depth_update(cdd->vc.ar);

				if (cdd->vc.rv3d->depths != NULL) {
					cdd->project.use_depth = true;
				}
				else {
					BKE_report(op->reports, RPT_WARNING, "Unable to access depth buffer, using view plane");
					cdd->project.use_depth = false;
				}
			}

			/* use view plane (when set or as fallback when surface can't be found) */
			if (cdd->project.use_depth == false) {
				plane_co = ED_view3d_cursor3d_get(cdd->vc.scene, v3d);;
				plane_no = rv3d->viewinv[2];
				cdd->project.use_plane = true;
			}

			if (cdd->project.use_depth && (cdd->curve_type != CU_POLY)) {
				cdd->sample.use_substeps = true;
			}
		}

		if (cdd->project.use_plane) {
			normalize_v3_v3(cdd->project.plane, plane_no);
			cdd->project.plane[3] = -dot_v3v3(cdd->project.plane, plane_co);
		}
	}

	if (is_modal == false) {
		curve_draw_event_add_first(op, event);
	}

	/* add temp handler */
	WM_event_add_modal_handler(C, op);

	return OPERATOR_RUNNING_MODAL;
}

static void curve_draw_cancel(bContext *UNUSED(C), wmOperator *op)
{
	curve_draw_exit(op);
}


/* Modal event handling of frame changing */
static int curve_draw_modal(bContext *C, wmOperator *op, const wmEvent *event)
{
	int ret = OPERATOR_RUNNING_MODAL;
	struct CurveDrawData *cdd = op->customdata;

	UNUSED_VARS(C, op);

	if (event->type == cdd->init_event_type) {
		if (event->val == KM_RELEASE) {
			ED_region_tag_redraw(cdd->vc.ar);

			curve_draw_exec_precalc(op);

			curve_draw_stroke_to_operator(op);

			curve_draw_exec(C, op);

			return OPERATOR_FINISHED;
		}
	}
	else if (ELEM(event->type, ESCKEY, RIGHTMOUSE)) {
		ED_region_tag_redraw(cdd->vc.ar);
		curve_draw_cancel(C, op);
		return OPERATOR_CANCELLED;
	}
	else if (ELEM(event->type, LEFTMOUSE)) {
		if (event->val == KM_PRESS) {
			curve_draw_event_add_first(op, event);
		}
	}
	else if (ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE)) {
		if (cdd->state == CURVE_DRAW_PAINTING) {
			const float mval_fl[2] = {UNPACK2(event->mval)};
			if (len_squared_v2v2(mval_fl, cdd->prev.mouse) > SQUARE(STROKE_SAMPLE_DIST_MIN_PX)) {
				curve_draw_event_add(op, event);
			}
		}
	}

	return ret;
}

void CURVE_OT_draw(wmOperatorType *ot)
{
	/* identifiers */
	ot->name = "Draw Curve";
	ot->idname = "CURVE_OT_draw";
	ot->description = "Draw a freehand spline";

	/* api callbacks */
	ot->exec = curve_draw_exec;
	ot->invoke = curve_draw_invoke;
	ot->cancel = curve_draw_cancel;
	ot->modal = curve_draw_modal;
	ot->poll = ED_operator_editcurve;

	/* flags */
	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;

	/* properties */
	PropertyRNA *prop;

	prop = RNA_def_float_distance(
	        ot->srna, "error_threshold", 0.0f, 0.0f, 10.0f, "Error",
	        "Error distance threshold (in object units)",
	        0.0001f, 10.0f);
	RNA_def_property_ui_range(prop, 0.0, 10, 1, 4);

	prop = RNA_def_float_distance(
	        ot->srna, "corner_angle", DEG2RADF(70.0f), 0.0f, M_PI, "Corner Angle", "", 0.0f, M_PI);
	RNA_def_property_subtype(prop, PROP_ANGLE);

	prop = RNA_def_collection_runtime(ot->srna, "stroke", &RNA_OperatorStrokeElement, "Stroke", "");
	RNA_def_property_flag(prop, PROP_SKIP_SAVE);

	prop = RNA_def_boolean(ot->srna, "wait_for_input", true, "Wait for Input", "");
	RNA_def_property_flag(prop, PROP_HIDDEN | PROP_SKIP_SAVE);
}

/** \} */