Sam Spilsbury
11 years ago
committed by
Kristian Høgsberg
parent
4a4704a7d0
commit
619859ce90
@ -0,0 +1,317 @@ |
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/*
|
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* Copyright © 2012 Intel Corporation |
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* |
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* Permission to use, copy, modify, distribute, and sell this software and |
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* its documentation for any purpose is hereby granted without fee, provided |
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* that the above copyright notice appear in all copies and that both that |
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* copyright notice and this permission notice appear in supporting |
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* documentation, and that the name of the copyright holders not be used in |
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* advertising or publicity pertaining to distribution of the software |
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* without specific, written prior permission. The copyright holders make |
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* no representations about the suitability of this software for any |
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* purpose. It is provided "as is" without express or implied warranty. |
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* |
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* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS |
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* SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND |
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* FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY |
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* SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER |
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* RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF |
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* CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS 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 <GLES2/gl2.h> |
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#include "vertex-clipping.h" |
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GLfloat |
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float_difference(GLfloat a, GLfloat 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 GLfloat max_diff = 4.0f * FLT_MIN; |
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static const GLfloat max_rel_diff = 4.0e-5; |
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GLfloat diff = a - b; |
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GLfloat 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 GLfloat |
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clip_intersect_y(GLfloat p1x, GLfloat p1y, GLfloat p2x, GLfloat p2y, |
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GLfloat x_arg) |
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{ |
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GLfloat a; |
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GLfloat 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 GLfloat |
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clip_intersect_x(GLfloat p1x, GLfloat p1y, GLfloat p2x, GLfloat p2y, |
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GLfloat y_arg) |
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{ |
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GLfloat a; |
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GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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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GLfloat x, GLfloat y, GLfloat clip_x) |
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{ |
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GLfloat 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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GLfloat x, GLfloat y, GLfloat clip_y) |
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{ |
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GLfloat 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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GLfloat *dst_x, GLfloat *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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GLfloat *dst_x, GLfloat *dst_y) |
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{ |
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enum path_transition trans; |
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int i; |
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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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GLfloat *dst_x, GLfloat *dst_y) |
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{ |
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enum path_transition trans; |
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int i; |
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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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GLfloat *dst_x, GLfloat *dst_y) |
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{ |
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enum path_transition trans; |
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int i; |
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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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GLfloat *dst_x, GLfloat *dst_y) |
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{ |
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enum path_transition trans; |
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int i; |
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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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GLfloat *ex, |
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GLfloat *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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GLfloat *ex, |
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GLfloat *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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@ -0,0 +1,65 @@ |
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/*
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* Copyright © 2012 Intel Corporation |
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* |
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* Permission to use, copy, modify, distribute, and sell this software and |
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* its documentation for any purpose is hereby granted without fee, provided |
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* that the above copyright notice appear in all copies and that both that |
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* copyright notice and this permission notice appear in supporting |
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* documentation, and that the name of the copyright holders not be used in |
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* advertising or publicity pertaining to distribution of the software |
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* without specific, written prior permission. The copyright holders make |
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* no representations about the suitability of this software for any |
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* purpose. It is provided "as is" without express or implied warranty. |
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* |
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* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS |
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* SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND |
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* FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY |
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* SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER |
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* RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF |
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* CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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#ifndef _WESTON_VERTEX_CLIPPING_H |
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#define _WESTON_VERTEX_CLIPPING_H |
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#include <GLES2/gl2.h> |
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struct polygon8 { |
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GLfloat x[8]; |
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GLfloat y[8]; |
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int n; |
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}; |
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struct clip_context { |
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struct { |
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GLfloat x; |
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GLfloat y; |
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} prev; |
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struct { |
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GLfloat x1, y1; |
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GLfloat x2, y2; |
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} clip; |
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struct { |
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GLfloat *x; |
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GLfloat *y; |
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} vertices; |
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}; |
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GLfloat |
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float_difference(GLfloat a, GLfloat 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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GLfloat *ex, |
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GLfloat *ey); |
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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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GLfloat *ex, |
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GLfloat *ey);\
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#endif |
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