//creation expression floats partcles
　　vector $ppos = spray_particleShape.position;
　　float $pu = $ppos.x;
　　float $pv = $ppos.z;
　　float $samp[] = `colorAtPoint -o RGBA -u $pu -v $pv oceanShader1`;
　　float $py = $samp[3];

　　//set initial particle position on ocean surface
　　spray_particleShape.position = <<$pu, $py, $pv>>;
　　我们还要对粒子的寿命进行控制

spray_particleShape.lifespanPP = rand(0.5, 2);

　　对粒子的速度进行控制。

　　//runtime expression for ocean spray

　　//check wave surface height
　　vector $ppos = spray_particleShape.position;
　　float $pu = $ppos.x;
　　float $pv = $ppos.z;
　　float $samp[] = `colorAtPoint -o A -u $pu -v $pv oceanShader1`;
　　float $py = $samp[0];

　　//clamp lower particle altitude to wave height
　　if($ppos.y <= $py) {
　　spray_particleShape.position = <<$pu, $py, $pv>>;
　　}
　　//drive particle down when it's too high
　　else if($ppos.y > $py + ocean_emitterPlane.sprayHeight) {
　　vector $pvel = spray_particleShape.velocity;
　　spray_particleShape.velocity = <<$pvel.x, $pvel.y - ocean_emitterPlane.sprayPull, $pvel.z>>;
　　};