paint_stroke.c

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/*
 * ***** 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.
 *
 * The Original Code is Copyright (C) 2009 by Nicholas Bishop
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): Jason Wilkins, Tom Musgrove.
 *
 * ***** END GPL LICENSE BLOCK *****
 *
 */

#include "MEM_guardedalloc.h"

#include "BLI_math.h"
#include "BLI_utildefines.h"

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

#include "RNA_access.h"

#include "BKE_context.h"
#include "BKE_paint.h"
#include "BKE_brush.h"

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

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

#include "ED_screen.h"
#include "ED_view3d.h"

#include "paint_intern.h"
/* still needed for sculpt_stroke_get_location, should be
   removed eventually (TODO) */
#include "sculpt_intern.h"

#include <float.h>
#include <math.h>

typedef struct PaintStroke {
        void *mode_data;
        void *smooth_stroke_cursor;
        wmTimer *timer;

        /* Cached values */
        ViewContext vc;
        bglMats mats;
        Brush *brush;

        float last_mouse_position[2];

        /* Set whether any stroke step has yet occurred
           e.g. in sculpt mode, stroke doesn't start until cursor
           passes over the mesh */
        int stroke_started;
        /* event that started stroke, for modal() return */
        int event_type;
        
        StrokeGetLocation get_location;
        StrokeTestStart test_start;
        StrokeUpdateStep update_step;
        StrokeDone done;
} PaintStroke;

/*** Cursor ***/
static void paint_draw_smooth_stroke(bContext *C, int x, int y, void *customdata) 
{
        Brush *brush = paint_brush(paint_get_active(CTX_data_scene(C)));
        PaintStroke *stroke = customdata;

        glColor4ubv(paint_get_active(CTX_data_scene(C))->paint_cursor_col);
        glEnable(GL_LINE_SMOOTH);
        glEnable(GL_BLEND);

        if(stroke && brush && (brush->flag & BRUSH_SMOOTH_STROKE)) {
                ARegion *ar = CTX_wm_region(C);
                sdrawline(x, y, (int)stroke->last_mouse_position[0] - ar->winrct.xmin,
                          (int)stroke->last_mouse_position[1] - ar->winrct.ymin);
        }

        glDisable(GL_BLEND);
        glDisable(GL_LINE_SMOOTH);
}

typedef struct Snapshot {
        float size[3];
        float ofs[3];
        float rot;
        int brush_size;
        int winx;
        int winy;
        int brush_map_mode;
        int curve_changed_timestamp;
} Snapshot;

static int same_snap(Snapshot* snap, Brush* brush, ViewContext* vc)
{
        MTex* mtex = &brush->mtex;

        return 
                (mtex->tex &&
                    mtex->ofs[0] == snap->ofs[0] &&
                    mtex->ofs[1] == snap->ofs[1] &&
                    mtex->ofs[2] == snap->ofs[2] &&
                    mtex->size[0] == snap->size[0] &&
                    mtex->size[1] == snap->size[1] &&
                    mtex->size[2] == snap->size[2] &&
                    mtex->rot == snap->rot) &&
                ((mtex->brush_map_mode == MTEX_MAP_MODE_FIXED && brush_size(brush) <= snap->brush_size) || (brush_size(brush) == snap->brush_size)) && // make brush smaller shouldn't cause a resample
                mtex->brush_map_mode == snap->brush_map_mode &&
                vc->ar->winx == snap->winx &&
                vc->ar->winy == snap->winy;
}

static void make_snap(Snapshot* snap, Brush* brush, ViewContext* vc)
{
        if (brush->mtex.tex) {
                snap->brush_map_mode = brush->mtex.brush_map_mode;
                copy_v3_v3(snap->ofs, brush->mtex.ofs);
                copy_v3_v3(snap->size, brush->mtex.size);
                snap->rot = brush->mtex.rot;
        }
        else {
                snap->brush_map_mode = -1;
                snap->ofs[0]= snap->ofs[1]= snap->ofs[2]= -1;
                snap->size[0]= snap->size[1]= snap->size[2]= -1;
                snap->rot = -1;
        }

        snap->brush_size = brush_size(brush);
        snap->winx = vc->ar->winx;
        snap->winy = vc->ar->winy;
}

static int load_tex(Sculpt *sd, Brush* br, ViewContext* vc)
{
        static GLuint overlay_texture = 0;
        static int init = 0;
        static int tex_changed_timestamp = -1;
        static int curve_changed_timestamp = -1;
        static Snapshot snap;
        static int old_size = -1;

        GLubyte* buffer = NULL;

        int size;
        int j;
        int refresh;

#ifndef _OPENMP
        (void)sd; /* quied unused warning */
#endif
        
        if (br->mtex.brush_map_mode == MTEX_MAP_MODE_TILED && !br->mtex.tex) return 0;
        
        refresh = 
                !overlay_texture ||
                (br->mtex.tex && 
                    (!br->mtex.tex->preview ||
                      br->mtex.tex->preview->changed_timestamp[0] != tex_changed_timestamp)) ||
                !br->curve ||
                br->curve->changed_timestamp != curve_changed_timestamp ||
                !same_snap(&snap, br, vc);

        if (refresh) {
                if (br->mtex.tex && br->mtex.tex->preview)
                        tex_changed_timestamp = br->mtex.tex->preview->changed_timestamp[0];

                if (br->curve)
                        curve_changed_timestamp = br->curve->changed_timestamp;

                make_snap(&snap, br, vc);

                if (br->mtex.brush_map_mode == MTEX_MAP_MODE_FIXED) {
                        int s = brush_size(br);
                        int r = 1;

                        for (s >>= 1; s > 0; s >>= 1)
                                r++;

                        size = (1<<r);

                        if (size < 256)
                                size = 256;

                        if (size < old_size)
                                size = old_size;
                }
                else
                        size = 512;

                if (old_size != size) {
                        if (overlay_texture) {
                                glDeleteTextures(1, &overlay_texture);
                                overlay_texture = 0;
                        }

                        init = 0;

                        old_size = size;
                }

                buffer = MEM_mallocN(sizeof(GLubyte)*size*size, "load_tex");

                #pragma omp parallel for schedule(static) if (sd->flags & SCULPT_USE_OPENMP)
                for (j= 0; j < size; j++) {
                        int i;
                        float y;
                        float len;

                        for (i= 0; i < size; i++) {

                                // largely duplicated from tex_strength

                                const float rotation = -br->mtex.rot;
                                float radius = brush_size(br);
                                int index = j*size + i;
                                float x;
                                float avg;

                                x = (float)i/size;
                                y = (float)j/size;

                                x -= 0.5f;
                                y -= 0.5f;

                                if (br->mtex.brush_map_mode == MTEX_MAP_MODE_TILED) {
                                        x *= vc->ar->winx / radius;
                                        y *= vc->ar->winy / radius;
                                }
                                else {
                                        x *= 2;
                                        y *= 2;
                                }

                                len = sqrtf(x*x + y*y);

                                if ((br->mtex.brush_map_mode == MTEX_MAP_MODE_TILED) || len <= 1) {
                                        /* it is probably worth optimizing for those cases where 
                                           the texture is not rotated by skipping the calls to
                                           atan2, sqrtf, sin, and cos. */
                                        if (br->mtex.tex && (rotation > 0.001f || rotation < -0.001f)) {
                                                const float angle    = atan2f(y, x) + rotation;

                                                x = len * cosf(angle);
                                                y = len * sinf(angle);
                                        }

                                        x *= br->mtex.size[0];
                                        y *= br->mtex.size[1];

                                        x += br->mtex.ofs[0];
                                        y += br->mtex.ofs[1];

                                        avg = br->mtex.tex ? paint_get_tex_pixel(br, x, y) : 1;

                                        avg += br->texture_sample_bias;

                                        if (br->mtex.brush_map_mode == MTEX_MAP_MODE_FIXED)
                                                avg *= brush_curve_strength(br, len, 1); /* Falloff curve */

                                        buffer[index] = 255 - (GLubyte)(255*avg);
                                }
                                else {
                                        buffer[index] = 0;
                                }
                        }
                }

                if (!overlay_texture)
                        glGenTextures(1, &overlay_texture);
        }
        else {
                size= old_size;
        }

        glBindTexture(GL_TEXTURE_2D, overlay_texture);

        if (refresh) {
                if (!init) {
                        glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, size, size, 0, GL_ALPHA, GL_UNSIGNED_BYTE, buffer);
                        init = 1;
                }
                else {
                        glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, size, size, GL_ALPHA, GL_UNSIGNED_BYTE, buffer);
                }

                if (buffer)
                        MEM_freeN(buffer);
        }

        glEnable(GL_TEXTURE_2D);

        glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        if (br->mtex.brush_map_mode == MTEX_MAP_MODE_FIXED) {
                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
        }

        return 1;
}

static int project_brush_radius(RegionView3D* rv3d, float radius, float location[3], bglMats* mats)
{
        float view[3], nonortho[3], ortho[3], offset[3], p1[2], p2[2];

        ED_view3d_global_to_vector(rv3d, location, view);

        // create a vector that is not orthogonal to view

        if (fabsf(view[0]) < 0.1f) {
                nonortho[0] = view[0] + 1.0f;
                nonortho[1] = view[1];
                nonortho[2] = view[2];
        }
        else if (fabsf(view[1]) < 0.1f) {
                nonortho[0] = view[0];
                nonortho[1] = view[1] + 1.0f;
                nonortho[2] = view[2];
        }
        else {
                nonortho[0] = view[0];
                nonortho[1] = view[1];
                nonortho[2] = view[2] + 1.0f;
        }

        // get a vector in the plane of the view
        cross_v3_v3v3(ortho, nonortho, view);
        normalize_v3(ortho);

        // make a point on the surface of the brush tagent to the view
        mul_v3_fl(ortho, radius);
        add_v3_v3v3(offset, location, ortho);

        // project the center of the brush, and the tagent point to the view onto the screen
        projectf(mats, location, p1);
        projectf(mats, offset, p2);

        // the distance between these points is the size of the projected brush in pixels
        return len_v2v2(p1, p2);
}

static int sculpt_get_brush_geometry(bContext* C, int x, int y, int* pixel_radius,
                              float location[3])
{
        struct PaintStroke *stroke;
        float window[2];
        int hit;

        stroke = paint_stroke_new(C, NULL, NULL, NULL, NULL, 0);

        window[0] = x + stroke->vc.ar->winrct.xmin;
        window[1] = y + stroke->vc.ar->winrct.ymin;

        if(stroke->vc.obact->sculpt && stroke->vc.obact->sculpt->pbvh &&
           sculpt_stroke_get_location(C, stroke, location, window)) {
                *pixel_radius = project_brush_radius(stroke->vc.rv3d,
                                                     brush_unprojected_radius(stroke->brush),
                                                     location, &stroke->mats);

                if (*pixel_radius == 0)
                        *pixel_radius = brush_size(stroke->brush);

                mul_m4_v3(stroke->vc.obact->obmat, location);

                hit = 1;
        }
        else {
                Sculpt* sd    = CTX_data_tool_settings(C)->sculpt;
                Brush*  brush = paint_brush(&sd->paint);

                *pixel_radius = brush_size(brush);
                hit = 0;
        }

        paint_stroke_free(stroke);

        return hit;
}

/* Draw an overlay that shows what effect the brush's texture will
   have on brush strength */
/* TODO: sculpt only for now */
static void paint_draw_alpha_overlay(Sculpt *sd, Brush *brush,
                                     ViewContext *vc, int x, int y)
{
        rctf quad;

        /* check for overlay mode */
        if(!(brush->flag & BRUSH_TEXTURE_OVERLAY) ||
           !(ELEM(brush->mtex.brush_map_mode, MTEX_MAP_MODE_FIXED, MTEX_MAP_MODE_TILED)))
                return;

        /* save lots of GL state
           TODO: check on whether all of these are needed? */
        glPushAttrib(GL_COLOR_BUFFER_BIT|
                     GL_CURRENT_BIT|
                     GL_DEPTH_BUFFER_BIT|
                     GL_ENABLE_BIT|
                     GL_LINE_BIT|
                     GL_POLYGON_BIT|
                     GL_STENCIL_BUFFER_BIT|
                     GL_TRANSFORM_BIT|
                     GL_VIEWPORT_BIT|
                     GL_TEXTURE_BIT);

        if(load_tex(sd, brush, vc)) {
                glEnable(GL_BLEND);

                glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
                glDepthMask(GL_FALSE);
                glDepthFunc(GL_ALWAYS);

                glMatrixMode(GL_TEXTURE);
                glPushMatrix();
                glLoadIdentity();

                if(brush->mtex.brush_map_mode == MTEX_MAP_MODE_FIXED) {
                        /* brush rotation */
                        glTranslatef(0.5, 0.5, 0);
                        glRotatef((double)((brush->flag & BRUSH_RAKE) ?
                                   sd->last_angle : sd->special_rotation) * (180.0/M_PI),
                                  0.0, 0.0, 1.0);
                        glTranslatef(-0.5f, -0.5f, 0);

                        /* scale based on tablet pressure */
                        if(sd->draw_pressure && brush_use_size_pressure(brush)) {
                                glTranslatef(0.5f, 0.5f, 0);
                                glScalef(1.0f/sd->pressure_value, 1.0f/sd->pressure_value, 1);
                                glTranslatef(-0.5f, -0.5f, 0);
                        }

                        if(sd->draw_anchored) {
                                const float *aim = sd->anchored_initial_mouse;
                                const rcti *win = &vc->ar->winrct;
                                quad.xmin = aim[0]-sd->anchored_size - win->xmin;
                                quad.ymin = aim[1]-sd->anchored_size - win->ymin;
                                quad.xmax = aim[0]+sd->anchored_size - win->xmin;
                                quad.ymax = aim[1]+sd->anchored_size - win->ymin;
                        }
                        else {
                                const int radius= brush_size(brush);
                                quad.xmin = x - radius;
                                quad.ymin = y - radius;
                                quad.xmax = x + radius;
                                quad.ymax = y + radius;
                        }
                }
                else {
                        quad.xmin = 0;
                        quad.ymin = 0;
                        quad.xmax = vc->ar->winrct.xmax - vc->ar->winrct.xmin;
                        quad.ymax = vc->ar->winrct.ymax - vc->ar->winrct.ymin;
                }

                /* set quad color */
                glColor4f(U.sculpt_paint_overlay_col[0],
                          U.sculpt_paint_overlay_col[1],
                          U.sculpt_paint_overlay_col[2],
                          brush->texture_overlay_alpha / 100.0f);

                /* draw textured quad */
                glBegin(GL_QUADS);
                glTexCoord2f(0, 0);
                glVertex2f(quad.xmin, quad.ymin);
                glTexCoord2f(1, 0);
                glVertex2f(quad.xmax, quad.ymin);
                glTexCoord2f(1, 1);
                glVertex2f(quad.xmax, quad.ymax);
                glTexCoord2f(0, 1);
                glVertex2f(quad.xmin, quad.ymax);
                glEnd();

                glPopMatrix();
        }

        glPopAttrib();
}

/* Special actions taken when paint cursor goes over mesh */
/* TODO: sculpt only for now */
static void paint_cursor_on_hit(Sculpt *sd, Brush *brush, ViewContext *vc,
                                float location[3], float *visual_strength)
{
        float unprojected_radius, projected_radius;

        /* TODO: check whether this should really only be done when
           brush is over mesh? */
        if(sd->draw_pressure && brush_use_alpha_pressure(brush))
                (*visual_strength) *= sd->pressure_value;

        if(sd->draw_anchored)
                projected_radius = sd->anchored_size;
        else {
                if(brush->flag & BRUSH_ANCHORED)
                        projected_radius = 8;
                else
                        projected_radius = brush_size(brush);
        }
        unprojected_radius = paint_calc_object_space_radius(vc, location,
                                                            projected_radius);

        if(sd->draw_pressure && brush_use_size_pressure(brush))
                unprojected_radius *= sd->pressure_value;

        if(!brush_use_locked_size(brush))
                brush_set_unprojected_radius(brush, unprojected_radius);
}

static void paint_draw_cursor(bContext *C, int x, int y, void *UNUSED(unused))
{
        Paint *paint = paint_get_active(CTX_data_scene(C));
        Brush *brush = paint_brush(paint);
        ViewContext vc;
        float final_radius;
        float translation[2];
        float outline_alpha, *outline_col;
        
        /* set various defaults */
        translation[0] = x;
        translation[1] = y;
        outline_alpha = 0.5;
        outline_col = brush->add_col;
        final_radius = brush_size(brush);

        /* check that brush drawing is enabled */
        if(!(paint->flags & PAINT_SHOW_BRUSH))
                return;

        /* can't use stroke vc here because this will be called during
           mouse over too, not just during a stroke */     
        view3d_set_viewcontext(C, &vc);

        /* TODO: as sculpt and other paint modes are unified, this
           special mode of drawing will go away */
        if(vc.obact->sculpt) {
                Sculpt *sd = CTX_data_tool_settings(C)->sculpt;
                float location[3];
                int pixel_radius, hit;
                const float root_alpha = brush_alpha(brush);
                float visual_strength = root_alpha*root_alpha;
                const float min_alpha = 0.20f;
                const float max_alpha = 0.80f;

                /* this is probably here so that rake takes into
                   account the brush movements before the stroke
                   starts, but this doesn't really belong in draw code
                   (TODO) */
                {
                        const float u = 0.5f;
                        const float v = 1 - u;
                        const float r = 20;

                        const float dx = sd->last_x - x;
                        const float dy = sd->last_y - y;

                        if(dx*dx + dy*dy >= r*r) {
                                sd->last_angle = atan2(dx, dy);

                                sd->last_x = u*sd->last_x + v*x;
                                sd->last_y = u*sd->last_y + v*y;
                        }
                }

                /* test if brush is over the mesh */
                hit = sculpt_get_brush_geometry(C, x, y, &pixel_radius, location);

                /* draw overlay */
                paint_draw_alpha_overlay(sd, brush, &vc, x, y);

                if(brush_use_locked_size(brush))
                        brush_set_size(brush, pixel_radius);

                /* check if brush is subtracting, use different color then */
                /* TODO: no way currently to know state of pen flip or
                   invert key modifier without starting a stroke */
                if((!(brush->flag & BRUSH_INVERTED) ^
                    !(brush->flag & BRUSH_DIR_IN)) &&
                   ELEM5(brush->sculpt_tool, SCULPT_TOOL_DRAW,
                         SCULPT_TOOL_INFLATE, SCULPT_TOOL_CLAY,
                         SCULPT_TOOL_PINCH, SCULPT_TOOL_CREASE))
                        outline_col = brush->sub_col;

                /* only do if brush is over the mesh */
                if(hit)
                        paint_cursor_on_hit(sd, brush, &vc, location, &visual_strength);

                /* don't show effect of strength past the soft limit */
                if(visual_strength > 1)
                        visual_strength = 1;

                outline_alpha = ((paint->flags & PAINT_SHOW_BRUSH_ON_SURFACE) ?
                                 min_alpha + (visual_strength*(max_alpha-min_alpha)) : 0.50f);

                if(sd->draw_anchored) {
                        final_radius = sd->anchored_size;
                        translation[0] = sd->anchored_initial_mouse[0] - vc.ar->winrct.xmin;
                        translation[1] = sd->anchored_initial_mouse[1] - vc.ar->winrct.ymin;
                }
        }

        /* make lines pretty */
        glEnable(GL_BLEND);
        glEnable(GL_LINE_SMOOTH);

        /* set brush color */
        glColor4f(outline_col[0], outline_col[1], outline_col[2], outline_alpha);

        /* draw brush outline */
        glTranslatef(translation[0], translation[1], 0);
        glutil_draw_lined_arc(0.0, M_PI*2.0, final_radius, 40);
        glTranslatef(-translation[0], -translation[1], 0);

        /* restore GL state */
        glDisable(GL_BLEND);
        glDisable(GL_LINE_SMOOTH);
}

/* if this is a tablet event, return tablet pressure and set *pen_flip
   to 1 if the eraser tool is being used, 0 otherwise */
static float event_tablet_data(wmEvent *event, int *pen_flip)
{
        int erasor = 0;
        float pressure = 1;

        if(event->custom == EVT_DATA_TABLET) {
                wmTabletData *wmtab= event->customdata;

                erasor = (wmtab->Active == EVT_TABLET_ERASER);
                pressure = (wmtab->Active != EVT_TABLET_NONE) ? wmtab->Pressure : 1;
        }

        if(pen_flip)
                (*pen_flip) = erasor;

        return pressure;
}

/* Put the location of the next stroke dot into the stroke RNA and apply it to the mesh */
static void paint_brush_stroke_add_step(bContext *C, wmOperator *op, wmEvent *event, float mouse_in[2])
{
        Paint *paint = paint_get_active(CTX_data_scene(C));
        Brush *brush = paint_brush(paint);
        PaintStroke *stroke = op->customdata;
        float mouse[3];
        PointerRNA itemptr;
        float location[3];
        float pressure;
        int pen_flip;

        /* see if tablet affects event */
        pressure = event_tablet_data(event, &pen_flip);

        /* TODO: as sculpt and other paint modes are unified, this
           separation will go away */
        if(stroke->vc.obact->sculpt) {
                float delta[3];

                brush_jitter_pos(brush, mouse_in, mouse);

                /* XXX: meh, this is round about because
                   brush_jitter_pos isn't written in the best way to
                   be reused here */
                if(brush->flag & BRUSH_JITTER_PRESSURE) {
                        sub_v3_v3v3(delta, mouse, mouse_in);
                        mul_v3_fl(delta, pressure);
                        add_v3_v3v3(mouse, mouse_in, delta);
                }
        }
        else
                copy_v3_v3(mouse, mouse_in);

        /* TODO: can remove the if statement once all modes have this */
        if(stroke->get_location)
                stroke->get_location(C, stroke, location, mouse);
        else
                zero_v3(location);

        /* Add to stroke */
        RNA_collection_add(op->ptr, "stroke", &itemptr);

        RNA_float_set_array(&itemptr, "location", location);
        RNA_float_set_array(&itemptr, "mouse", mouse);
        RNA_boolean_set(&itemptr, "pen_flip", pen_flip);
        RNA_float_set(&itemptr, "pressure", pressure);

        stroke->last_mouse_position[0] = mouse[0];
        stroke->last_mouse_position[1] = mouse[1];

        stroke->update_step(C, stroke, &itemptr);
}

/* Returns zero if no sculpt changes should be made, non-zero otherwise */
static int paint_smooth_stroke(PaintStroke *stroke, float output[2], wmEvent *event)
{
        output[0] = event->x; 
        output[1] = event->y;

        if ((stroke->brush->flag & BRUSH_SMOOTH_STROKE) &&  
            !ELEM4(stroke->brush->sculpt_tool, SCULPT_TOOL_GRAB, SCULPT_TOOL_THUMB, SCULPT_TOOL_ROTATE, SCULPT_TOOL_SNAKE_HOOK) &&
            !(stroke->brush->flag & BRUSH_ANCHORED) &&
            !(stroke->brush->flag & BRUSH_RESTORE_MESH))
        {
                float u = stroke->brush->smooth_stroke_factor, v = 1.0f - u;
                float dx = stroke->last_mouse_position[0] - event->x, dy = stroke->last_mouse_position[1] - event->y;

                /* If the mouse is moving within the radius of the last move,
                   don't update the mouse position. This allows sharp turns. */
                if(dx*dx + dy*dy < stroke->brush->smooth_stroke_radius * stroke->brush->smooth_stroke_radius)
                        return 0;

                output[0] = event->x * v + stroke->last_mouse_position[0] * u;
                output[1] = event->y * v + stroke->last_mouse_position[1] * u;
        }

        return 1;
}

/* For brushes with stroke spacing enabled, moves mouse in steps
   towards the final mouse location. */
static int paint_space_stroke(bContext *C, wmOperator *op, wmEvent *event, const float final_mouse[2])
{
        PaintStroke *stroke = op->customdata;
        int cnt = 0;

        if(paint_space_stroke_enabled(stroke->brush)) {
                float mouse[2];
                float vec[2];
                float length, scale;

                copy_v2_v2(mouse, stroke->last_mouse_position);
                sub_v2_v2v2(vec, final_mouse, mouse);

                length = len_v2(vec);

                if(length > FLT_EPSILON) {
                        int steps;
                        int i;
                        float pressure= 1.0f;

                        /* XXX mysterious :) what has 'use size' do with this here... if you don't check for it, pressure fails */
                        if(brush_use_size_pressure(stroke->brush))
                                pressure = event_tablet_data(event, NULL);
                        
                        if(pressure > FLT_EPSILON) {
                                scale = (brush_size(stroke->brush)*pressure*stroke->brush->spacing/50.0f) / length;
                                if(scale > FLT_EPSILON) {
                                        mul_v2_fl(vec, scale);

                                        steps = (int)(1.0f / scale);

                                        for(i = 0; i < steps; ++i, ++cnt) {
                                                add_v2_v2(mouse, vec);
                                                paint_brush_stroke_add_step(C, op, event, mouse);
                                        }
                                }
                        }
                }
        }

        return cnt;
}

/**** Public API ****/

PaintStroke *paint_stroke_new(bContext *C,
                                  StrokeGetLocation get_location,
                                  StrokeTestStart test_start,
                                  StrokeUpdateStep update_step,
                                  StrokeDone done, int event_type)
{
        PaintStroke *stroke = MEM_callocN(sizeof(PaintStroke), "PaintStroke");

        stroke->brush = paint_brush(paint_get_active(CTX_data_scene(C)));
        view3d_set_viewcontext(C, &stroke->vc);
        view3d_get_transformation(stroke->vc.ar, stroke->vc.rv3d, stroke->vc.obact, &stroke->mats);

        stroke->get_location = get_location;
        stroke->test_start = test_start;
        stroke->update_step = update_step;
        stroke->done = done;
        stroke->event_type= event_type; /* for modal, return event */
        
        return stroke;
}

void paint_stroke_free(PaintStroke *stroke)
{
        MEM_freeN(stroke);
}

/* Returns zero if the stroke dots should not be spaced, non-zero otherwise */
int paint_space_stroke_enabled(Brush *br)
{
        return (br->flag & BRUSH_SPACE) &&
               !(br->flag & BRUSH_ANCHORED) &&
               !ELEM4(br->sculpt_tool, SCULPT_TOOL_GRAB, SCULPT_TOOL_THUMB, SCULPT_TOOL_ROTATE, SCULPT_TOOL_SNAKE_HOOK);
}

int paint_stroke_modal(bContext *C, wmOperator *op, wmEvent *event)
{
        PaintStroke *stroke = op->customdata;
        float mouse[2];
        int first= 0;

        // let NDOF motion pass through to the 3D view so we can paint and rotate simultaneously!
        // this isn't perfect... even when an extra MOUSEMOVE is spoofed, the stroke discards it
        // since the 2D deltas are zero -- code in this file needs to be updated to use the
        // post-NDOF_MOTION MOUSEMOVE
        if (event->type == NDOF_MOTION)
                return OPERATOR_PASS_THROUGH;

        if(!stroke->stroke_started) {
                stroke->last_mouse_position[0] = event->x;
                stroke->last_mouse_position[1] = event->y;
                stroke->stroke_started = stroke->test_start(C, op, event);

                if(stroke->stroke_started) {
                        stroke->smooth_stroke_cursor =
                                WM_paint_cursor_activate(CTX_wm_manager(C), paint_poll, paint_draw_smooth_stroke, stroke);

                        if(stroke->brush->flag & BRUSH_AIRBRUSH)
                                stroke->timer = WM_event_add_timer(CTX_wm_manager(C), CTX_wm_window(C), TIMER, stroke->brush->rate);
                }

                first= 1;
                //ED_region_tag_redraw(ar);
        }

        if(event->type == stroke->event_type && event->val == KM_RELEASE) {
                /* exit stroke, free data */
                if(stroke->smooth_stroke_cursor)
                        WM_paint_cursor_end(CTX_wm_manager(C), stroke->smooth_stroke_cursor);

                if(stroke->timer)
                        WM_event_remove_timer(CTX_wm_manager(C), CTX_wm_window(C), stroke->timer);

                stroke->done(C, stroke);
                MEM_freeN(stroke);
                return OPERATOR_FINISHED;
        }
        else if(first || ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE) || (event->type == TIMER && (event->customdata == stroke->timer))) {
                if(stroke->stroke_started) {
                        if(paint_smooth_stroke(stroke, mouse, event)) {
                                if(paint_space_stroke_enabled(stroke->brush)) {
                                        if(!paint_space_stroke(C, op, event, mouse)) {
                                                //ED_region_tag_redraw(ar);
                                        }
                                }
                                else {
                                        paint_brush_stroke_add_step(C, op, event, mouse);
                                }
                        }
                        else {
                                ;//ED_region_tag_redraw(ar);
                        }
                }
        }

        /* we want the stroke to have the first daub at the start location instead of waiting till we have moved the space distance */
        if(first &&
           stroke->stroke_started &&
           paint_space_stroke_enabled(stroke->brush) &&
           !(stroke->brush->flag & BRUSH_ANCHORED) &&
           !(stroke->brush->flag & BRUSH_SMOOTH_STROKE))
        {
                paint_brush_stroke_add_step(C, op, event, mouse);
        }
        
        return OPERATOR_RUNNING_MODAL;
}

int paint_stroke_exec(bContext *C, wmOperator *op)
{
        PaintStroke *stroke = op->customdata;

        /* only when executed for the first time */
        if(stroke->stroke_started == 0) {
                /* XXX stroke->last_mouse_position is unset, this may cause problems */
                stroke->test_start(C, op, NULL);
                stroke->stroke_started= 1;
        }

        RNA_BEGIN(op->ptr, itemptr, "stroke") {
                stroke->update_step(C, stroke, &itemptr);
        }
        RNA_END;

        stroke->done(C, stroke);

        MEM_freeN(stroke);
        op->customdata = NULL;

        return OPERATOR_FINISHED;
}

int paint_stroke_cancel(bContext *C, wmOperator *op)
{
        PaintStroke *stroke = op->customdata;

        if(stroke->done)
                stroke->done(C, stroke);

        MEM_freeN(stroke);
        op->customdata = NULL;

        return OPERATOR_CANCELLED;
}

ViewContext *paint_stroke_view_context(PaintStroke *stroke)
{
        return &stroke->vc;
}

void *paint_stroke_mode_data(struct PaintStroke *stroke)
{
        return stroke->mode_data;
}

void paint_stroke_set_mode_data(PaintStroke *stroke, void *mode_data)
{
        stroke->mode_data = mode_data;
}

int paint_poll(bContext *C)
{
        Paint *p = paint_get_active(CTX_data_scene(C));
        Object *ob = CTX_data_active_object(C);

        return p && ob && paint_brush(p) &&
                CTX_wm_area(C)->spacetype == SPACE_VIEW3D &&
                CTX_wm_region(C)->regiontype == RGN_TYPE_WINDOW;
}

void paint_cursor_start(bContext *C, int (*poll)(bContext *C))
{
        Paint *p = paint_get_active(CTX_data_scene(C));

        if(p && !p->paint_cursor)
                p->paint_cursor = WM_paint_cursor_activate(CTX_wm_manager(C), poll, paint_draw_cursor, NULL);
}