User Guide > Quickstart > Discover Houdini 

Discovering Houdini - Effects

To animate the Rocket you will work both with the objects transformation information and its shape. The basic liftoff will be created using keyframes set to the translation of the surface while a cartoon-like squash-stretch will be applied at the geometry (SOP) level to anticipate the lift-off.


Particles
Objective: To become familiar with a simple particle example.
Time: 10-15 minutes
Experience: Beginner
New Tools: Particles, parenting
To add flames to the rocket thruster, you will use the particle SOP. For both Houdini and Houdini Select, you can use Particle Systems that are useful for effects such as: Fire, Smoke, Gases, and Flocking simulations. With Houdini, you can use Particle Operations (POPs) for even more complex results.
Particle Thruster
Type T in the Viewport, and select: Generators > Geometry. Click with your \ to accept it. You see a generic 3D cube appear in the Viewport. Find the new geo1 object tile, and rename it to: ‘Flames.’
In the network pane, connect the Rocket to the Flames. This parents the flames to the rocket. Playback the animation to preview the new relationship. Go back to frame 1 when you are finished.
Particle Surface Emitter
Click on the moonscape tile with your \ and select Toggle Display to hide it.
Click with \ on the flames tile, and select Edit SOPS to enter the Flames object. Once inside, delete file1, and the generic box disappears. Change your view to a wireframe view then click on the See one/all objects button to see the rocket and flame at the same time.
You need some geometry to act as a source for particles. Press the T key and select Generators > Sphere. Set the sphere parameters to:
Primitive Type to NURBS
Radius to 0.25, 0.25, 0.25 (use ] on the Radius parameter to do three at a time)
Home the view (W h) then make it an ortho view (W o). Zoom in closely (W ]) to the exhaust area of the rocket in order to more precisely position the sphere.
To make things easier, enable Snapping from the Snap Menu.
Press the T key and select Filters > Transform, then press \ to accept the selection, Press t to call up the Translate Handle., and then drag the pivot so that it snaps to the centre of the bottom cap.
You don’t need the whole sphere, and you don’t want our particle source to intersect the blast shield either. Press T and select Filters > Carve then press the \ to accept the selection. Set the Parameters to:
First U to Off;
First V to On.
By dragging on the First V ring itself, or using the slider in parameters, tweak the First V Ring down so it no longer intersects the bottom cap (about 0.6).
Now that you have a satisfactory emitter surface, you will also need a surface for which the particles will Collide (i.e. the ‘moonscape’). You will bring it in from the moonscape Object.
Press T and select Generators > Object Merge. In the parameter pane for object_merge1, the Source 1 parameter should be set to the moonscape object. Also, set the Transform Object parameter at the bottom to: This Object. You should see the ground plane light up yellow to indicate that it is selected, and in place.
Adding the Particles
Press T and select Filters > Particle. The blue help text at the top of the Houdini window says, ‘Select the points to animate, and right-click to complete’, but right now, you have the ground plane selected instead of the sphere. Click with [ on the wireframe of the emitter sphere to select it; and then click with \ accept these as the points to animate.
Then the blue text says, ‘select the full collision geometry, and right-click to complete’ – so click with [ on the ground plane (it turns white), click it again with [ so it becomes yellow, and finally – click with \ to finish. The emitter disappears, and you get a small number of particles.
Click the Play button in the Playbar – you see a couple particles appear, but they do not break away from the emitting surface.
You need to specify the strength and direction of the force which moves the particles. While the animation is still playing, go into the Forces page of the particle1’s parameters, and use ] in the External Force - Y field to give us some thrust – a value of about -3.0 works well.
Turn off Ortho (o), Home the View (W h), and Zoom the View (W ]) as necessary. Playback the results to see the particles in motion.
Conclusion
You have now explored Houdini’s workspace and worked with some of its tools and operators. This workflow gives you an understanding of how the interface lets you build up procedural models interactively and then animate them at both the object and operator levels. These basic concepts will play a role in all of your work with Houdini as you explore all the tools available for animating in 3D.