331 lines
8.5 KiB
C
331 lines
8.5 KiB
C
/*
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* Copyright © 2012 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial
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* portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include <assert.h>
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#include <float.h>
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#include <math.h>
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#include "vertex-clipping.h"
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float
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float_difference(float a, float b)
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{
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/* http://www.altdevblogaday.com/2012/02/22/comparing-floating-point-numbers-2012-edition/ */
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static const float max_diff = 4.0f * FLT_MIN;
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static const float max_rel_diff = 4.0e-5;
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float diff = a - b;
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float adiff = fabsf(diff);
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if (adiff <= max_diff)
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return 0.0f;
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a = fabsf(a);
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b = fabsf(b);
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if (adiff <= (a > b ? a : b) * max_rel_diff)
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return 0.0f;
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return diff;
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}
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/* A line segment (p1x, p1y)-(p2x, p2y) intersects the line x = x_arg.
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* Compute the y coordinate of the intersection.
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*/
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static float
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clip_intersect_y(float p1x, float p1y, float p2x, float p2y,
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float x_arg)
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{
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float a;
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float diff = float_difference(p1x, p2x);
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/* Practically vertical line segment, yet the end points have already
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* been determined to be on different sides of the line. Therefore
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* the line segment is part of the line and intersects everywhere.
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* Return the end point, so we use the whole line segment.
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*/
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if (diff == 0.0f)
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return p2y;
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a = (x_arg - p2x) / diff;
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return p2y + (p1y - p2y) * a;
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}
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/* A line segment (p1x, p1y)-(p2x, p2y) intersects the line y = y_arg.
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* Compute the x coordinate of the intersection.
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*/
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static float
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clip_intersect_x(float p1x, float p1y, float p2x, float p2y,
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float y_arg)
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{
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float a;
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float diff = float_difference(p1y, p2y);
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/* Practically horizontal line segment, yet the end points have already
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* been determined to be on different sides of the line. Therefore
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* the line segment is part of the line and intersects everywhere.
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* Return the end point, so we use the whole line segment.
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*/
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if (diff == 0.0f)
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return p2x;
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a = (y_arg - p2y) / diff;
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return p2x + (p1x - p2x) * a;
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}
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enum path_transition {
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PATH_TRANSITION_OUT_TO_OUT = 0,
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PATH_TRANSITION_OUT_TO_IN = 1,
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PATH_TRANSITION_IN_TO_OUT = 2,
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PATH_TRANSITION_IN_TO_IN = 3,
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};
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static void
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clip_append_vertex(struct clip_context *ctx, float x, float y)
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{
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*ctx->vertices.x++ = x;
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*ctx->vertices.y++ = y;
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}
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static enum path_transition
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path_transition_left_edge(struct clip_context *ctx, float x, float y)
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{
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return ((ctx->prev.x >= ctx->clip.x1) << 1) | (x >= ctx->clip.x1);
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}
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static enum path_transition
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path_transition_right_edge(struct clip_context *ctx, float x, float y)
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{
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return ((ctx->prev.x < ctx->clip.x2) << 1) | (x < ctx->clip.x2);
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}
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static enum path_transition
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path_transition_top_edge(struct clip_context *ctx, float x, float y)
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{
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return ((ctx->prev.y >= ctx->clip.y1) << 1) | (y >= ctx->clip.y1);
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}
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static enum path_transition
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path_transition_bottom_edge(struct clip_context *ctx, float x, float y)
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{
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return ((ctx->prev.y < ctx->clip.y2) << 1) | (y < ctx->clip.y2);
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}
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static void
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clip_polygon_leftright(struct clip_context *ctx,
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enum path_transition transition,
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float x, float y, float clip_x)
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{
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float yi;
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switch (transition) {
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case PATH_TRANSITION_IN_TO_IN:
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clip_append_vertex(ctx, x, y);
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break;
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case PATH_TRANSITION_IN_TO_OUT:
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yi = clip_intersect_y(ctx->prev.x, ctx->prev.y, x, y, clip_x);
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clip_append_vertex(ctx, clip_x, yi);
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break;
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case PATH_TRANSITION_OUT_TO_IN:
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yi = clip_intersect_y(ctx->prev.x, ctx->prev.y, x, y, clip_x);
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clip_append_vertex(ctx, clip_x, yi);
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clip_append_vertex(ctx, x, y);
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break;
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case PATH_TRANSITION_OUT_TO_OUT:
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/* nothing */
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break;
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default:
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assert(0 && "bad enum path_transition");
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}
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ctx->prev.x = x;
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ctx->prev.y = y;
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}
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static void
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clip_polygon_topbottom(struct clip_context *ctx,
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enum path_transition transition,
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float x, float y, float clip_y)
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{
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float xi;
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switch (transition) {
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case PATH_TRANSITION_IN_TO_IN:
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clip_append_vertex(ctx, x, y);
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break;
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case PATH_TRANSITION_IN_TO_OUT:
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xi = clip_intersect_x(ctx->prev.x, ctx->prev.y, x, y, clip_y);
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clip_append_vertex(ctx, xi, clip_y);
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break;
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case PATH_TRANSITION_OUT_TO_IN:
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xi = clip_intersect_x(ctx->prev.x, ctx->prev.y, x, y, clip_y);
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clip_append_vertex(ctx, xi, clip_y);
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clip_append_vertex(ctx, x, y);
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break;
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case PATH_TRANSITION_OUT_TO_OUT:
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/* nothing */
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break;
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default:
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assert(0 && "bad enum path_transition");
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}
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ctx->prev.x = x;
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ctx->prev.y = y;
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}
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static void
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clip_context_prepare(struct clip_context *ctx, const struct polygon8 *src,
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float *dst_x, float *dst_y)
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{
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ctx->prev.x = src->x[src->n - 1];
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ctx->prev.y = src->y[src->n - 1];
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ctx->vertices.x = dst_x;
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ctx->vertices.y = dst_y;
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}
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static int
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clip_polygon_left(struct clip_context *ctx, const struct polygon8 *src,
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float *dst_x, float *dst_y)
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{
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enum path_transition trans;
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int i;
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if (src->n < 2)
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return 0;
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clip_context_prepare(ctx, src, dst_x, dst_y);
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for (i = 0; i < src->n; i++) {
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trans = path_transition_left_edge(ctx, src->x[i], src->y[i]);
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clip_polygon_leftright(ctx, trans, src->x[i], src->y[i],
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ctx->clip.x1);
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}
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return ctx->vertices.x - dst_x;
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}
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static int
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clip_polygon_right(struct clip_context *ctx, const struct polygon8 *src,
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float *dst_x, float *dst_y)
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{
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enum path_transition trans;
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int i;
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if (src->n < 2)
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return 0;
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clip_context_prepare(ctx, src, dst_x, dst_y);
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for (i = 0; i < src->n; i++) {
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trans = path_transition_right_edge(ctx, src->x[i], src->y[i]);
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clip_polygon_leftright(ctx, trans, src->x[i], src->y[i],
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ctx->clip.x2);
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}
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return ctx->vertices.x - dst_x;
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}
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static int
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clip_polygon_top(struct clip_context *ctx, const struct polygon8 *src,
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float *dst_x, float *dst_y)
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{
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enum path_transition trans;
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int i;
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if (src->n < 2)
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return 0;
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clip_context_prepare(ctx, src, dst_x, dst_y);
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for (i = 0; i < src->n; i++) {
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trans = path_transition_top_edge(ctx, src->x[i], src->y[i]);
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clip_polygon_topbottom(ctx, trans, src->x[i], src->y[i],
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ctx->clip.y1);
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}
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return ctx->vertices.x - dst_x;
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}
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static int
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clip_polygon_bottom(struct clip_context *ctx, const struct polygon8 *src,
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float *dst_x, float *dst_y)
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{
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enum path_transition trans;
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int i;
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if (src->n < 2)
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return 0;
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clip_context_prepare(ctx, src, dst_x, dst_y);
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for (i = 0; i < src->n; i++) {
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trans = path_transition_bottom_edge(ctx, src->x[i], src->y[i]);
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clip_polygon_topbottom(ctx, trans, src->x[i], src->y[i],
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ctx->clip.y2);
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}
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return ctx->vertices.x - dst_x;
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}
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#define max(a, b) (((a) > (b)) ? (a) : (b))
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#define min(a, b) (((a) > (b)) ? (b) : (a))
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#define clip(x, a, b) min(max(x, a), b)
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int
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clip_simple(struct clip_context *ctx,
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struct polygon8 *surf,
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float *ex,
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float *ey)
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{
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int i;
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for (i = 0; i < surf->n; i++) {
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ex[i] = clip(surf->x[i], ctx->clip.x1, ctx->clip.x2);
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ey[i] = clip(surf->y[i], ctx->clip.y1, ctx->clip.y2);
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}
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return surf->n;
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}
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int
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clip_transformed(struct clip_context *ctx,
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struct polygon8 *surf,
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float *ex,
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float *ey)
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{
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struct polygon8 polygon;
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int i, n;
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polygon.n = clip_polygon_left(ctx, surf, polygon.x, polygon.y);
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surf->n = clip_polygon_right(ctx, &polygon, surf->x, surf->y);
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polygon.n = clip_polygon_top(ctx, surf, polygon.x, polygon.y);
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surf->n = clip_polygon_bottom(ctx, &polygon, surf->x, surf->y);
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/* Get rid of duplicate vertices */
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ex[0] = surf->x[0];
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ey[0] = surf->y[0];
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n = 1;
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for (i = 1; i < surf->n; i++) {
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if (float_difference(ex[n - 1], surf->x[i]) == 0.0f &&
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float_difference(ey[n - 1], surf->y[i]) == 0.0f)
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continue;
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ex[n] = surf->x[i];
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ey[n] = surf->y[i];
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n++;
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}
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if (float_difference(ex[n - 1], surf->x[0]) == 0.0f &&
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float_difference(ey[n - 1], surf->y[0]) == 0.0f)
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n--;
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return n;
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}
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