+const v3s16 g_27dirs[27] =
+{
+ // +right, +top, +back
+ v3s16( 0, 0, 1), // back
+ v3s16( 0, 1, 0), // top
+ v3s16( 1, 0, 0), // right
+ v3s16( 0, 0,-1), // front
+ v3s16( 0,-1, 0), // bottom
+ v3s16(-1, 0, 0), // left
+ // 6
+ v3s16(-1, 1, 0), // top left
+ v3s16( 1, 1, 0), // top right
+ v3s16( 0, 1, 1), // top back
+ v3s16( 0, 1,-1), // top front
+ v3s16(-1, 0, 1), // back left
+ v3s16( 1, 0, 1), // back right
+ v3s16(-1, 0,-1), // front left
+ v3s16( 1, 0,-1), // front right
+ v3s16(-1,-1, 0), // bottom left
+ v3s16( 1,-1, 0), // bottom right
+ v3s16( 0,-1, 1), // bottom back
+ v3s16( 0,-1,-1), // bottom front
+ // 18
+ v3s16(-1, 1, 1), // top back-left
+ v3s16( 1, 1, 1), // top back-right
+ v3s16(-1, 1,-1), // top front-left
+ v3s16( 1, 1,-1), // top front-right
+ v3s16(-1,-1, 1), // bottom back-left
+ v3s16( 1,-1, 1), // bottom back-right
+ v3s16(-1,-1,-1), // bottom front-left
+ v3s16( 1,-1,-1), // bottom front-right
+ // 26
+ v3s16(0,0,0),
+};
+
+static unsigned long next = 1;
+
+/* RAND_MAX assumed to be 32767 */
+int myrand(void)
+{
+ next = next * 1103515245 + 12345;
+ return((unsigned)(next/65536) % 32768);
+}
+
+void mysrand(unsigned seed)
+{
+ next = seed;
+}
+
+/*
+ blockpos: position of block in block coordinates
+ camera_pos: position of camera in nodes
+ camera_dir: an unit vector pointing to camera direction
+ range: viewing range
+*/
+bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir, f32 range,
+ f32 *distance_ptr)
+{
+ v3s16 blockpos_nodes = blockpos_b * MAP_BLOCKSIZE;
+
+ // Block center position
+ v3f blockpos(
+ ((float)blockpos_nodes.X + MAP_BLOCKSIZE/2) * BS,
+ ((float)blockpos_nodes.Y + MAP_BLOCKSIZE/2) * BS,
+ ((float)blockpos_nodes.Z + MAP_BLOCKSIZE/2) * BS
+ );
+
+ // Block position relative to camera
+ v3f blockpos_relative = blockpos - camera_pos;
+
+ // Distance in camera direction (+=front, -=back)
+ f32 dforward = blockpos_relative.dotProduct(camera_dir);
+
+ // Total distance
+ f32 d = blockpos_relative.getLength();
+
+ if(distance_ptr)
+ *distance_ptr = d;
+
+ // If block is far away, it's not in sight
+ if(d > range * BS)
+ return false;
+
+ // Maximum radius of a block
+ f32 block_max_radius = 0.5*1.44*1.44*MAP_BLOCKSIZE*BS;
+
+ // If block is (nearly) touching the camera, don't
+ // bother validating further (that is, render it anyway)
+ if(d > block_max_radius * 1.5)
+ {
+ // Cosine of the angle between the camera direction
+ // and the block direction (camera_dir is an unit vector)
+ f32 cosangle = dforward / d;
+
+ // Compensate for the size of the block
+ // (as the block has to be shown even if it's a bit off FOV)
+ // This is an estimate.
+ cosangle += block_max_radius / dforward;
+
+ // If block is not in the field of view, skip it
+ //if(cosangle < cos(FOV_ANGLE/2))
+ if(cosangle < cos(FOV_ANGLE/2. * 4./3.))
+ return false;
+ }
+
+ return true;
+}