Tracepro中up vector和normal vector的定义1

1.normal vector：When the normal vector is defined as (0,0,1) the grid of rays will be parallel to the Z-axis, but facing the positive Z direction。
解释：这其实决定了grid source面的倾斜方向和光线发射方向。
2.up vector：The up vector determines which direction will be considered the height (or the “up” direction). So, a grid source with an up vector defined as (0,1,0) will have a grid of rays with height dimension along the Y-axis。
解释：这其实决定了height在那个方向。
例如：


当热，如果你的grid source是圆形的话，两者其实并没有什么差别。