1 files changed, 72 insertions, 0 deletions
diff --git a/generator/pamtris/boundaries.h b/generator/pamtris/boundaries.h
new file mode 100644
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+++ b/generator/pamtris/boundaries.h
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+#ifndef BOUNDARIES_H_INCLUDED
+#define BOUNDARIES_H_INCLUDED
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "triangle.h"
+
+typedef struct boundary_info {
+/*----------------------------------------------------------------------------
+  Information about visible triangle rows' boundaries. Also see the
+  "boundary buffer functions" below.
+
+  A "visible" triangle row is one which:
+
+    1. Corresponds to a frame buffer row whose index (from top to bottom) is
+       equal to or greater than 0 and smaller than the image height; and
+
+    2. Has at least some of its pixels between the frame buffer columns whose
+       index (from left to right) is equal to or greater than 0 and smaller
+       than the image width.
+-----------------------------------------------------------------------------*/
+    int16_t start_scanline;
+        /* Index of the frame buffer scanline which contains the first visible
+           row of the current triangle, if there is any such row. If not, it
+           contains the value -1.
+        */
+
+    int16_t num_upper_rows;
+        /* The number of visible rows in the upper part of the triangle. The
+           upper part of a triangle is composed of all the rows starting from
+           the top vertex down to the middle vertex, but not including this
+           last one.
+        */
+
+    int16_t num_lower_rows;
+        /* The number of visible rows in the lower part of the triangle. The
+           lower part of a triangle is composed of all the rows from the
+           middle vertex to the bottom vertex -- all inclusive.
+        */
+
+    int16_t * buffer;
+        /* This is the "boundary buffer": a pointer to an array of int16_t's
+           where each consecutive pair of values indicates, in this order, the
+           columns of the left and right boundary pixels for a particular
+           visible triangle row. Those boundaries are inclusive on both sides
+           and may be outside the limits of the frame buffer. This field is
+           initialized and freed by the functions "init_boundary_buffer" and
+           "free_boundary_buffer", respectively.
+        */
+} boundary_info;
+
+void
+init_boundary_buffer(boundary_info * const bdi,
+                     int16_t         const height);
+
+void
+free_boundary_buffer(boundary_info *);
+
+bool
+gen_triangle_boundaries(Xy              const xy,
+                        boundary_info * const bdi,
+                        int16_t         const width,
+                        int16_t         const height);
+
+void
+get_triangle_boundaries(uint16_t              const row_index,
+                        int32_t *             const left,
+                        int32_t *             const right,
+                        const boundary_info * const bdi);
+
+#endif