+float sdLine( vec3 p, vec3 a, vec3 b )
+{
+ vec3 pa = p - a;
+ vec3 ba = b - a;
+
+ float h = clamp( dot(pa,ba)/dot(ba,ba), 0.0, 1.0 );
+ return length( pa - ba*h );
+}
+
+float compute_board_shadow()
+{
+ // player shadow
+ float dist_to_player = max( 0.0, sdLine( aWorldCo, uBoard0, uBoard1 )-0.1 );
+ float player_shadow = max( 1.0-dist_to_player*2.7, 0.0 );
+ player_shadow *= player_shadow*player_shadow*player_shadow;
+
+ return 1.0 - player_shadow*0.8;
+}
+