/*
* ***** 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) 2012 Blender Foundation.
* All rights reserved.
*
* The Original Code is: all of this file.
*
* Contributor(s): Peter Larabell.
*
* ***** END GPL LICENSE BLOCK *****
*/
/** \file raskter.c
* \ingroup RASKTER
*/
#include
#include "raskter.h"
/* from BLI_utildefines.h */
#define MIN2(x, y) ( (x) < (y) ? (x) : (y) )
#define MAX2(x, y) ( (x) > (y) ? (x) : (y) )
struct PolyVert {
int x;
int y;
};
struct e_Status {
int x;
int ybeg;
int xshift;
int xdir;
int drift;
int drift_inc;
int drift_dec;
int num;
struct e_Status *e_next;
};
struct r_BufferStats {
float *buf;
int sizex;
int sizey;
int ymin;
int ymax;
int xmin;
int xmax;
};
struct r_FillContext {
struct e_Status *all_edges, *possible_edges;
struct r_BufferStats rb;
};
/*
* Sort all the edges of the input polygon by Y, then by X, of the "first" vertex encountered.
* This will ensure we can scan convert the entire poly in one pass.
*
* Really the poly should be clipped to the frame buffer's dimensions here for speed of drawing
* just the poly. Since the DEM code could end up being coupled with this, we'll keep it separate
* for now.
*/
static void preprocess_all_edges(struct r_FillContext *ctx,
struct PolyVert *verts, int num_verts, struct e_Status *open_edge)
{
int i;
int xbeg;
int ybeg;
int xend;
int yend;
int dx;
int dy;
int temp_pos;
int xdist;
struct e_Status *e_new;
struct e_Status *next_edge;
struct e_Status **next_edge_ref;
struct PolyVert *v;
/* set up pointers */
v = verts;
ctx->all_edges = NULL;
/* initialize some boundaries */
ctx->rb.xmax = v[0].x;
ctx->rb.xmin = v[0].x;
ctx->rb.ymax = v[0].y;
ctx->rb.ymin = v[0].y;
/* loop all verts */
for (i = 0; i < num_verts; i++) {
/* determine beginnings and endings of edges, linking last vertex to first vertex */
xbeg = v[i].x;
ybeg = v[i].y;
/* keep track of our x and y bounds */
if (xbeg >= ctx->rb.xmax) {
ctx->rb.xmax = xbeg;
}
else if (xbeg <= ctx->rb.xmin) {
ctx->rb.xmin = xbeg;
}
if (ybeg >= ctx->rb.ymax) {
ctx->rb.ymax= ybeg;
}
else if (ybeg <= ctx->rb.ymin) {
ctx->rb.ymin=ybeg;
}
if (i) {
/* we're not at the last vert, so end of the edge is the previous vertex */
xend = v[i - 1].x;
yend = v[i - 1].y;
}
else {
/* we're at the first vertex, so the "end" of this edge is the last vertex */
xend = v[num_verts - 1].x;
yend = v[num_verts - 1].y;
}
/* make sure our edges are facing the correct direction */
if (ybeg > yend) {
/* flip the Xs */
temp_pos = xbeg;
xbeg = xend;
xend = temp_pos;
/* flip the Ys */
temp_pos = ybeg;
ybeg = yend;
yend = temp_pos;
}
/* calculate y delta */
dy = yend - ybeg;
/* dont draw horizontal lines directly, they are scanned as part of the edges they connect, so skip em. :) */
if (dy) {
/* create the edge and determine it's slope (for incremental line drawing) */
e_new = open_edge++;
/* calculate x delta */
dx = xend - xbeg;
if (dx > 0) {
e_new->xdir = 1;
xdist = dx;
}
else {
e_new->xdir = -1;
xdist = -dx;
}
e_new->x = xbeg;
e_new->ybeg = ybeg;
e_new->num = dy;
e_new->drift_dec = dy;
/* calculate deltas for incremental drawing */
if (dx >= 0) {
e_new->drift = 0;
}
else {
e_new->drift = -dy + 1;
}
if (dy >= xdist) {
e_new->drift_inc = xdist;
e_new->xshift = 0;
}
else {
e_new->drift_inc = xdist % dy;
e_new->xshift = (xdist / dy) * e_new->xdir;
}
next_edge_ref = &ctx->all_edges;
/* link in all the edges, in sorted order */
for (;;) {
next_edge = *next_edge_ref;
if (!next_edge || (next_edge->ybeg > ybeg) || ((next_edge->ybeg == ybeg) && (next_edge->x >= xbeg))) {
e_new->e_next = next_edge;
*next_edge_ref = e_new;
break;
}
next_edge_ref = &next_edge->e_next;
}
}
}
}
/*
* This function clips drawing to the frame buffer. That clipping will likely be moved into the preprocessor
* for speed, but waiting on final design choices for curve-data before eliminating data the DEM code will need
* if it ends up being coupled with this function.
*/
static int rast_scan_fill(struct r_FillContext *ctx, struct PolyVert *verts, int num_verts, float intensity)
{
int x_curr; /* current pixel position in X */
int y_curr; /* current scan line being drawn */
int yp; /* y-pixel's position in frame buffer */
int swixd = 0; /* whether or not edges switched position in X */
float *cpxl; /* pixel pointers... */
float *mpxl;
float *spxl;
struct e_Status *e_curr; /* edge pointers... */
struct e_Status *e_temp;
struct e_Status *edgbuf;
struct e_Status **edgec;
/*
* If the number of verts specified to render as a polygon is less than 3,
* return immediately. Obviously we cant render a poly with sides < 3. The
* return for this we set to 1, simply so it can be distinguished from the
* next place we could return, /home/guest/blender-svn/soc-2011-tomato/intern/raskter/raskter.
* which is a failure to allocate memory.
*/
if (num_verts < 3) {
return(1);
}
/*
* Try to allocate an edge buffer in memory. needs to be the size of the edge tracking data
* multiplied by the number of edges, which is always equal to the number of verts in
* a 2D polygon. Here we return 0 to indicate a memory allocation failure, as opposed to a 1 for
* the preceeding error, which was a rasterization request on a 2D poly with less than
* 3 sides.
*/
if ((edgbuf = (struct e_Status *)(malloc(sizeof(struct e_Status) * num_verts))) == NULL) {
return(0);
}
/*
* Do some preprocessing on all edges. This constructs a table structure in memory of all
* the edge properties and can "flip" some edges so sorting works correctly.
*/
preprocess_all_edges(ctx, verts, num_verts, edgbuf);
/* can happen with a zero area mask */
if (ctx->all_edges == NULL) {
free(edgbuf);
return(1);
}
/*
* Set the pointer for tracking the edges currently in processing to NULL to make sure
* we don't get some crazy value after initialization.
*/
ctx->possible_edges = NULL;
/*
* Loop through all scan lines to be drawn. Since we sorted by Y values during
* preprocess_all_edges(), we can already exact values for the lowest and
* highest Y values we could possibly need by induction. The preprocessing sorted
* out edges by Y position, we can cycle the current edge being processed once
* it runs out of Y pixels. When we have no more edges, meaning the current edge
* is NULL after setting the "current" edge to be the previous current edge's
* "next" edge in the Y sorted edge connection chain, we can stop looping Y values,
* since we can't possibly have more scan lines if we ran out of edges. :)
*
* TODO: This clips Y to the frame buffer, which should be done in the preprocessor, but for now is done here.
* Will get changed once DEM code gets in.
*/
for (y_curr = ctx->all_edges->ybeg; (ctx->all_edges || ctx->possible_edges); y_curr++) {
/*
* Link any edges that start on the current scan line into the list of
* edges currently needed to draw at least this, if not several, scan lines.
*/
/*
* Set the current edge to the beginning of the list of edges to be rasterized
* into this scan line.
*
* We could have lots of edge here, so iterate over all the edges needed. The
* preprocess_all_edges() function sorted edges by X within each chunk of Y sorting
* so we safely cycle edges to thier own "next" edges in order.
*
* At each iteration, make sure we still have a non-NULL edge.
*/
for (edgec = &ctx->possible_edges; ctx->all_edges && (ctx->all_edges->ybeg == y_curr);) {
x_curr = ctx->all_edges->x; /* Set current X position. */
for (;;) { /* Start looping edges. Will break when edges run out. */
e_curr = *edgec; /* Set up a current edge pointer. */
if (!e_curr || (e_curr->x >= x_curr)) { /* If we have an no edge, or we need to skip some X-span, */
e_temp = ctx->all_edges->e_next; /* set a temp "next" edge to test. */
*edgec = ctx->all_edges; /* Add this edge to the list to be scanned. */
ctx->all_edges->e_next = e_curr; /* Set up the next edge. */
edgec = &ctx->all_edges->e_next; /* Set our list to the next edge's location in memory. */
ctx->all_edges = e_temp; /* Skip the NULL or bad X edge, set pointer to next edge. */
break; /* Stop looping edges (since we ran out or hit empty X span. */
}
else {
edgec = &e_curr->e_next; /* Set the pointer to the edge list the "next" edge. */
}
}
}
/*
* Determine the current scan line's offset in the pixel buffer based on its Y position.
* Basically we just multiply the current scan line's Y value by the number of pixels in each line.
*/
yp = y_curr * ctx->rb.sizex;
/*
* Set a "scan line pointer" in memory. The location of the buffer plus the row offset.
*/
spxl = ctx->rb.buf + (yp);
/*
* Set up the current edge to the first (in X) edge. The edges which could possibly be in this
* list were determined in the preceeding edge loop above. They were already sorted in X by the
* initial processing function.
*
* At each iteration, test for a NULL edge. Since we'll keep cycling edge's to their own "next" edge
* we will eventually hit a NULL when the list runs out.
*/
for (e_curr = ctx->possible_edges; e_curr; e_curr = e_curr->e_next) {
/*
* Calculate a span of pixels to fill on the current scan line.
*
* Set the current pixel pointer by adding the X offset to the scan line's start offset.
* Cycle the current edge the next edge.
* Set the max X value to draw to be one less than the next edge's first pixel. This way we are
* sure not to ever get into a situation where we have overdraw. (drawing the same pixel more than
* one time because it's on a vertex connecting two edges)
*
* Then blast through all the pixels in the span, advancing the pointer and setting the color to white.
*
* TODO: Here we clip to the scan line, this is not efficient, and should be done in the preprocessor,
* but for now it is done here until the DEM code comes in.
*/
/* set up xmin and xmax bounds on this scan line */
cpxl = spxl + MAX2(e_curr->x, 0);
e_curr = e_curr->e_next;
mpxl = spxl + MIN2(e_curr->x, ctx->rb.sizex) - 1;
if ((y_curr >= 0) && (y_curr < ctx->rb.sizey)) {
/* draw the pixels. */
for (; cpxl <= mpxl; *cpxl++ += intensity) {}
}
}
/*
* Loop through all edges of polygon that could be hit by this scan line,
* and figure out their x-intersections with the next scan line.
*
* Either A.) we wont have any more edges to test, or B.) we just add on the
* slope delta computed in preprocessing step. Since this draws non-antialiased
* polygons, we dont have fractional positions, so we only move in x-direction
* when needed to get all the way to the next pixel over...
*/
for (edgec = &ctx->possible_edges; (e_curr = *edgec);) {
if (!(--(e_curr->num))) {
*edgec = e_curr->e_next;
}
else {
e_curr->x += e_curr->xshift;
if ((e_curr->drift += e_curr->drift_inc) > 0) {
e_curr->x += e_curr->xdir;
e_curr->drift -= e_curr->drift_dec;
}
edgec = &e_curr->e_next;
}
}
/*
* It's possible that some edges may have crossed during the last step, so we'll be sure
* that we ALWAYS intersect scan lines in order by shuffling if needed to make all edges
* sorted by x-intersection coordinate. We'll always scan through at least once to see if
* edges crossed, and if so, we set the 'swixd' flag. If 'swixd' gets set on the initial
* pass, then we know we need to sort by x, so then cycle through edges again and perform
* the sort.-
*/
if (ctx->possible_edges) {
for (edgec = &ctx->possible_edges; (e_curr = *edgec)->e_next; edgec = &(*edgec)->e_next) {
/* if the current edge hits scan line at greater X than the next edge, we need to exchange the edges */
if (e_curr->x > e_curr->e_next->x) {
*edgec = e_curr->e_next;
/* exchange the pointers */
e_temp = e_curr->e_next->e_next;
e_curr->e_next->e_next = e_curr;
e_curr->e_next = e_temp;
/* set flag that we had at least one switch */
swixd = 1;
}
}
/* if we did have a switch, look for more (there will more if there was one) */
for (;;) {
/* reset exchange flag so it's only set if we encounter another one */
swixd = 0;
for (edgec = &ctx->possible_edges; (e_curr = *edgec)->e_next; edgec = &(*edgec)->e_next) {
/* again, if current edge hits scan line at higher X than next edge, exchange the edges and set flag */
if (e_curr->x > e_curr->e_next->x) {
*edgec = e_curr->e_next;
/* exchange the pointers */
e_temp = e_curr->e_next->e_next;
e_curr->e_next->e_next = e_curr;
e_curr->e_next = e_temp;
/* flip the exchanged flag */
swixd = 1;
}
}
/* if we had no exchanges, we're done reshuffling the pointers */
if (!swixd) {
break;
}
}
}
}
free(edgbuf);
return 1;
}
int PLX_raskterize(float(*base_verts)[2], int num_base_verts,
float *buf, int buf_x, int buf_y)
{
int i; /* i: Loop counter. */
struct PolyVert *ply; /* ply: Pointer to a list of integer buffer-space vertex coordinates. */
struct r_FillContext ctx = {0};
const float buf_x_f = (float)(buf_x);
const float buf_y_f = (float)(buf_y);
/*
* Allocate enough memory for our PolyVert list. It'll be the size of the PolyVert
* data structure multiplied by the number of base_verts.
*
* In the event of a failure to allocate the memory, return 0, so this error can
* be distinguished as a memory allocation error.
*/
if ((ply = (struct PolyVert *)(malloc(sizeof(struct PolyVert) * num_base_verts))) == NULL) {
return(0);
}
ctx.rb.buf = buf; /* Set the output buffer pointer. */
ctx.rb.sizex = buf_x; /* Set the output buffer size in X. (width) */
ctx.rb.sizey = buf_y; /* Set the output buffer size in Y. (height) */
/*
* Loop over all verts passed in to be rasterized. Each vertex's X and Y coordinates are
* then converted from normalized screen space (0.0 <= POS <= 1.0) to integer coordinates
* in the buffer-space coordinates passed in inside buf_x and buf_y.
*
* It's worth noting that this function ONLY outputs fully white pixels in a mask. Every pixel
* drawn will be 1.0f in value, there is no anti-aliasing.
*/
for (i = 0; i < num_base_verts; i++) { /* Loop over all base_verts. */
ply[i].x = (int)((base_verts[i][0] * buf_x_f) + 0.5f); /* Range expand normalized X to integer buffer-space X. */
ply[i].y = (int)((base_verts[i][1] * buf_y_f) + 0.5f); /* Range expand normalized Y to integer buffer-space Y. */
}
i = rast_scan_fill(&ctx, ply, num_base_verts,1.0f); /* Call our rasterizer, passing in the integer coords for each vert. */
free(ply); /* Free the memory allocated for the integer coordinate table. */
return(i); /* Return the value returned by the rasterizer. */
}