+/* Check whether the object is already *in* the tile. If so, the tile
+ * is non-solid. Otherwise, if the object is "above" (south slopes)
+ * or "below" (north slopes), the tile will be solid. */
+bool Tile::check_position_unisolid (const Rectf& obj_bbox,
+ const Rectf& tile_bbox) const
+{
+ int slope_info;
+ float tile_x;
+ float tile_y;
+ float gradient;
+ float delta_x;
+ float delta_y;
+ float obj_x = 0.0;
+ float obj_y = 0.0;
+
+ /* If this is not a slope, this is - again - easy */
+ if (!this->is_slope())
+ {
+ int dir = this->getData() & Tile::UNI_DIR_MASK;
+
+ return ((dir == Tile::UNI_DIR_NORTH) && ((obj_bbox.get_bottom() - SHIFT_DELTA) <= tile_bbox.get_top() ))
+ || ((dir == Tile::UNI_DIR_SOUTH) && ((obj_bbox.get_top() + SHIFT_DELTA) >= tile_bbox.get_bottom()))
+ || ((dir == Tile::UNI_DIR_WEST ) && ((obj_bbox.get_right() - SHIFT_DELTA) <= tile_bbox.get_left() ))
+ || ((dir == Tile::UNI_DIR_EAST ) && ((obj_bbox.get_left() + SHIFT_DELTA) >= tile_bbox.get_right() ));
+ }
+
+ /* There are 20 different cases. For each case, calculate a line that
+ * describes the slope's surface. The line is defined by x, y, and m, the
+ * gradient. */
+ slope_info = this->getData();
+ switch (slope_info
+ & (AATriangle::DIRECTION_MASK | AATriangle::DEFORM_MASK))
+ {
+ case AATriangle::SOUTHWEST:
+ case AATriangle::SOUTHWEST | AATriangle::DEFORM_TOP:
+ case AATriangle::SOUTHWEST | AATriangle::DEFORM_LEFT:
+ case AATriangle::NORTHEAST:
+ case AATriangle::NORTHEAST | AATriangle::DEFORM_TOP:
+ case AATriangle::NORTHEAST | AATriangle::DEFORM_LEFT:
+ tile_x = tile_bbox.get_left();
+ tile_y = tile_bbox.get_top();
+ gradient = 1.0;
+ break;
+
+ case AATriangle::SOUTHEAST:
+ case AATriangle::SOUTHEAST | AATriangle::DEFORM_TOP:
+ case AATriangle::SOUTHEAST | AATriangle::DEFORM_RIGHT:
+ case AATriangle::NORTHWEST:
+ case AATriangle::NORTHWEST | AATriangle::DEFORM_TOP:
+ case AATriangle::NORTHWEST | AATriangle::DEFORM_RIGHT:
+ tile_x = tile_bbox.get_right();
+ tile_y = tile_bbox.get_top();
+ gradient = -1.0;
+ break;
+
+ case AATriangle::SOUTHEAST | AATriangle::DEFORM_BOTTOM:
+ case AATriangle::SOUTHEAST | AATriangle::DEFORM_LEFT:
+ case AATriangle::NORTHWEST | AATriangle::DEFORM_BOTTOM:
+ case AATriangle::NORTHWEST | AATriangle::DEFORM_LEFT:
+ tile_x = tile_bbox.get_left();
+ tile_y = tile_bbox.get_bottom();
+ gradient = -1.0;
+ break;
+
+ case AATriangle::SOUTHWEST | AATriangle::DEFORM_BOTTOM:
+ case AATriangle::SOUTHWEST | AATriangle::DEFORM_RIGHT:
+ case AATriangle::NORTHEAST | AATriangle::DEFORM_BOTTOM:
+ case AATriangle::NORTHEAST | AATriangle::DEFORM_RIGHT:
+ tile_x = tile_bbox.get_right();
+ tile_y = tile_bbox.get_bottom();
+ gradient = 1.0;
+ break;
+
+ default:
+ assert (23 == 42);
+ return 0;
+ }
+
+ /* delta_x, delta_y: Gradient aware version of SHIFT_DELTA. Here, we set the
+ * sign of the values only. Also, we determine here which corner of the
+ * object's bounding box is the interesting one for us. */
+ delta_x = 1.0 * SHIFT_DELTA;
+ delta_y = 1.0 * SHIFT_DELTA;
+ switch (slope_info & AATriangle::DIRECTION_MASK)
+ {
+ case AATriangle::SOUTHWEST:
+ delta_x *= 1.0;
+ delta_y *= -1.0;
+ obj_x = obj_bbox.get_left();
+ obj_y = obj_bbox.get_bottom();
+ break;
+
+ case AATriangle::SOUTHEAST:
+ delta_x *= -1.0;
+ delta_y *= -1.0;
+ obj_x = obj_bbox.get_right();
+ obj_y = obj_bbox.get_bottom();
+ break;
+
+ case AATriangle::NORTHWEST:
+ delta_x *= 1.0;
+ delta_y *= 1.0;
+ obj_x = obj_bbox.get_left();
+ obj_y = obj_bbox.get_top();
+ break;
+
+ case AATriangle::NORTHEAST:
+ delta_x *= -1.0;
+ delta_y *= 1.0;
+ obj_x = obj_bbox.get_right();
+ obj_y = obj_bbox.get_top();
+ break;
+ }
+
+ /* Adapt the delta_x, delta_y and the gradient for the 26.6 deg and 63.4 deg
+ * cases. */
+ switch (slope_info & AATriangle::DEFORM_MASK)
+ {
+ case 0:
+ delta_x *= .70710678118654752440; /* 1/sqrt(2) */
+ delta_y *= .70710678118654752440; /* 1/sqrt(2) */
+ break;
+
+ case AATriangle::DEFORM_BOTTOM:
+ case AATriangle::DEFORM_TOP:
+ delta_x *= .44721359549995793928; /* 1/sqrt(5) */
+ delta_y *= .89442719099991587856; /* 2/sqrt(5) */
+ gradient *= 0.5;
+ break;
+
+ case AATriangle::DEFORM_LEFT:
+ case AATriangle::DEFORM_RIGHT:
+ delta_x *= .89442719099991587856; /* 2/sqrt(5) */
+ delta_y *= .44721359549995793928; /* 1/sqrt(5) */
+ gradient *= 2.0;
+ break;
+ }
+
+ /* With a south slope, check if all points are above the line. If one point
+ * isn't, the slope is not solid. => You can pass through a south-slope from
+ * below but not from above. */
+ if (((slope_info & AATriangle::DIRECTION_MASK) == AATriangle::SOUTHWEST)
+ || ((slope_info & AATriangle::DIRECTION_MASK) == AATriangle::SOUTHEAST))
+ {
+ return !is_below_line(tile_x, tile_y, gradient, obj_x + delta_x, obj_y + delta_y);
+ }
+ /* northwest or northeast. Same as above, but inverted. You can pass from top
+ * to bottom but not vice versa. */
+ else
+ {
+ return !is_above_line (tile_x, tile_y, gradient, obj_x + delta_x, obj_y + delta_y);
+ }
+} /* int check_position_unisolid */
+
+bool Tile::is_solid (const Rectf& tile_bbox, const Rectf& position, const Vector& movement) const
+{
+ if (!(attributes & SOLID))
+ return false;
+
+ if (!(attributes & UNISOLID))
+ return true;
+
+ return check_movement_unisolid (movement) &&
+ check_position_unisolid (position, tile_bbox);
+} /* bool Tile::is_solid */
+
+/* vim: set sw=2 sts=2 et : */