The Origin tab can control more than the bounds in which sprites and lines spawn.
Example: An effect was needed where sprites moved outward from a center point. You could set values under Motion for Left and Up, but this would create a square shape when viewed from the top.
To get around this, apply motion only in the forward axis and use Origin to adjust where the forward axis is. This can be accomplished by Generating the normal from effect origin of an effect segment and selecting Spawn on Surface of a shape such as a cylinder or sphere. Depending on the size of the origin min/max bounds, the sprite particles will emit from what appears to be a bubble or from a point. If the origin bounds are very small, it will appear as though the sprites are emitting from a single point.
This same technique can be used with lines, and will give them a direction to point in. A good example is effects/weapons/machinegun/impact_default.fx. The side_streaks segment uses a cylinder origin with Spawn on Surface checked. Giving the Origin only a min value for in the forward axis ensures a consistent angle forward, while a range of left and up values ensure a random selection around the circumference of the cylinder. As the forward value grows larger in relation to the left and up values, the angle of the line segments grows steeper. As the forward value grows smaller in relation to the left and up values, the angle of the line segments grows shallower. (Note on the machinegun effect: Since the forward origin value is β0.2, Invert Normals is checked so the lines point the proper direction.)
A good way to achieve the angle you are looking for is to make sure your particle count is high temporarily so itβs easier to see what is going on. Remember that once you find your angle, you can adjust the numbers down to decimal values so that the angle is projected from a single point.
Example: Forward value of 5, Left and Up min/max values of β10/10. This will generate a cylinder 5 units tall with a diameter of 10 units. If you wish this effect to emit from a point, drop the values to: Forward 0.05 and Left/Up min/max β0.1/0.1
Sample Origin values and visual description.
Example A:
Forward min |
5 |
Left min/max |
-10/10 |
Up min/max |
-10/10 |
Example B:
Forward min |
10 |
Left min/max |
-10/10 |
Up min/max |
-10/10 |
Example C:
Forward min |
0.1 |
Left min/max |
-0.1/0.1 |
Up min/max |
-0.1/0.1 |