To create an animation in Blender like the one I am currently showing on the screen, where an object is animated using keyframes and interacts with Rigid Body objects, it is necessary to set the manually animated object as a Rigid Body Passive with the Animated option selected.
Video Transcript
Hello everyone! To create an animation in Blender like the one I am currently showing on the screen, where an object is animated using keyframes and interacts with Rigid Body objects, it is necessary to set the manually animated object as a Rigid Body Passive with the Animated option selected.
Let's go step by step through the operations needed to create this animation.
All objects are parented to the billiard table, but this is not suitable for the physics simulation. Therefore, first, let's select all objects except the billiard table, and clear their parent relationships by pressing ALT P and choosing the Clear Parent and Keep Transformation option from the menu that appears on the screen.
Let's create a new Collection in which we will place all the billiard balls. This allows us to quickly select them all with a right-click and Select Objects. This will be useful when we need to modify certain parameters of the Rigid Body for all billiard balls.
Now let's provide a Rigid Body Passive component to the billiard table, then set the collision shape to Mesh, allowing the balls to fall into the pockets.
All billiard balls will be active physical objects, so select them all, open the toolbox, and type Rigid Body Add Active to provide this component to all billiard balls.
With my initial scene settings, the billiard balls are too light. To change the mass of all billiard balls at once, first, select them all, then press the ALT key and, while holding it down, click on the Mass field in the Rigid Body tab. Now, release the ALT key and type an appropriate value, such as 0.16 kg. This weight will then be assigned to all billiard balls.
Remember this ALT key trick if you need to modify options for multiple objects. In this scenario, this operation might come in handy to change other parameters common to all billiard balls, such as Damping, Bounciness, and other physical parameters found in the Surface Response and Dynamics sections of the Rigid Body tab.
Use this trick again to change the Collision Shape of all billiard balls to Sphere.
Now we can position the cue stick at the first frame of the animation and insert an animation keyframe for the initial position.
The cue stick should have a Rigid Body component of the Passive type, and most importantly, it should have the Animated option selected, as mentioned at the beginning of this tutorial.
Let's also switch to the Local Axis display, noting that we can move the cue stick forward or backward by grabbing it along its local X-axis.
Let's go to the sixth frame of the animation, adjust the cue stick to strike the white ball, and record this animation keyframe.
Let's advance another 3 frames to move the cue stick away from the table and record its new position with another animation keyframe.
Before starting the Bake for the physics simulation, save the scene as a new file on disk.
Return to the first frame of the Timeline, open the Scene tab in the Properties Editor, and in the Rigid Body World Cache section, click on Bake All Dynamics.
Once the Rigid Body simulation Bake is complete, review the resulting animation in the 3D Viewport.
If the motion of the billiard balls appears too slow, too fast, or excessively powerful, you can adjust various parameters, such as the initial movement speed of the cue stick or other physical parameters like the Friction value of the table. I advise against lowering the Friction value of the balls too much, as they may slide on the table rather than roll!
After each modification, clear all Bakes in the Cache section of Rigid Body World, return to the first frame of the Timeline, save the file, and the physics simulation Bake again.
The default value for the Bounciness parameter is 0. Set it to 1 for the table, and increase it slightly (without exaggerating) for the billiard balls to avoid clustering at the bottom without rebounds. Remember that you can change the value of a parameter for all objects in a multiple selection by simply pressing the ALT key when clicking on the parameter, then releasing the ALT key and entering the value.
Another aspect to keep in mind is the impact speed of the cue stick on the white ball because it is proportional to the applied force. There are two ways to make the cue stick movement faster.
The first method is to bring the impact keyframe closer to the first frame of the animation. You can do this by selecting the diamonds representing keyframes in the timeline and moving them forward or backward with the G key.
The second method involves starting the cue stick from a more backward position, placing it further back along its X-axis in the first keyframe of the animation. In this case, you will need to record the keyframe again.
Both methods can be used together, experimenting until you find the combination that produces the result you are most satisfied with. A good result is achieved through a balanced combination of initial distance, impact speed, and settings for Friction and Bounciness.
When conducting experiments, remember to return to the first frame, clear the Bake, save the file, and perform a new Bake of the Rigid Body simulation.
Well, that's all! I hope this tutorial has been helpful! See you soon!