Animated Lens Flare

Particle effect properties, such as the rotation angle of lens flare streaks, can be animated easily using key framing: simply enter a suitable attribute value on the property window, with animation recording turned on. In this example, we show how to set up a more complicated system: the rotation angle of flares based on the cameras orientation.

Tutorial level: Advanced

Example project: 'tutorprojects/postprocessing/rotatingflares'

1. First create the camera: activate the camera tool and hit 'Accept' to record the current view to the camera. Turn animation recording on and go to the last frame of the animation. Open the camera's property window, go to the 'Gen' tab and change the 'Rotate' fields first component by say 180 degrees (for example from zero to 180 degrees). Then turn animation recording off. Camera heading will now change during the animation half a revolution.

2. Activate the particle tool and create some random 1D particles, then hit 'Accept' button to finish the tool. Open the property window, go to 'Spec' tab and turn off the 'Rendering/Scanline' option. Particles will be rendered using only post effect flares.

3. Go to the Post particle effects tab of the Select window. Drag&drop the 'Stars' effect (or another lens flare) to the view to map it to selected particles. Render the view to make sure that flares work as expected (if not, make sure that the view window's post effect configuration includes particle effect rendering).

4. While the 'Stars' effect is still selected, right click and pick the popup menu 'Make Choreographable' on the select window. Next open the Choreographs window from the 'Animation' pulldown menu.

5. On the Choreography window, select the 'stars:chor0' item and switch to the 'Input' tab. Then go to the Select window, switch to the object geometry tab and drag&drop the camera object on top of the 'stars:chor0' item. The 'Input' area is changed to show camera attributes. Select 'Rotate Quaternion.x' from the attribute list - in other words, the cameras heading angle will act as the input for the flare animation.

6. Switch to the 'Time lines' tab of the choreography window. Define a time line 'Start'=-180, 'End'=180 using the numeric fields on the bottom of the window.

7. Next we define what to animate. Switch to the 'Animateable Attributes' tab and pick 'Star Angle' from the list. Check the 'Animated' option above the list.

8. Finally go to the 'Animation Curves' tab. If you don't see a curve gadget there, select 'Show all key frames' from the left part of the window and activate the Star Angle' sub item. Then move the mouse over the curve gadget and select 'Create predefined curve/45 degree. curve' from its popup menu. A diagonal line appears; activate the start point and change its Y value to -180 degrees. Activate the end point and change the Y value to 180 degrees. In other words, the curve maps the cameras heading angle to the identical lens flare streak angle. Other kinds of curves could be used as well, of course.

The animation is now ready. Render it to an AVI file to see rotating streaks.