1.6. In the Material Editor, make sure the popcorn map is open. Click on "Bitmap”, and select Mask from the Map Browser. Choose "Keep old map as sub-map” in the "Replace Map” dialog. In the new Mask material, your popcorn map is set as Map, so drag that do the Mask slot, and choose "Swap”.
1.7. Click the Map slot, and choose Gradient Ramp from the Map Browser. Set Gradient Type to Radial. Right-click the left flag, choose "Edit properties” and change the color from black to white, right-click the center flag and choose "Delete”, and right-click the right flag and choose "Edit properties”.
1.8. Press the None slot to open the Map Browser and choose Smoke. In the Smoke Map settings, enter Size 5, and Exponent 1.
1.9. Create a Target Direct light in the top viewport, so it lights the teapot from behind, and place the target in the center of the teapot. On the light's "Intensity...” rollout, activate Use Far Attenuation, and adjust the Near and Far values so the range covers the whole teapot and the particles. Under Directional Parameters, adjust the Hotspot/Beam so all the particles are covered. Now for the magic: in the light's Advanced Settings rollout, click "Ambient Only”. This will make the light ignore the polygons' angles, which is exactly what we want.
1.10. Render that out to see the fluffiest teapot!
(hint: switch to Mental Ray to double render speed)
What we've done here is fake ray-marching. The fake part is that we ignore how far the light has travelled inside the cloud, and instead concentrate only on how far the light travels in space. For our purposes, it's close enough.
First, we'll create a camera that chases an airplane through a tunnel. Later, we'll turn that tunnel into clouds. If you think you've already spent too many hours of your life creating tunnel effects, move onto chapter 3, but skim chapter 2 to make a note of the dimensions used.
2.1. Delete the teapot and the light from before, but keep the camera, particle system and the material.
2.2. Create an s-shaped spline like this, using four bezier points. Note the shape in the Top and Left viewports. Be careful with the bezier handles – no sharp corners! And since we don't want any jittering in the camera, increase the interpolation to 20, and de-check Optimize. (actually, we do want jittering, but not this kind... more on this later!)
2.3. The first point in my curve is at 0,0,0, and the last is at 50,400,-100. This isn't crucial, but the closer your scale is to this, the easier it will be to match the sizes of particles and procedural maps later in the tutorial.
2.4. Select the camera, and add a Path Constraint by going to the Motion rollout, expand the Assign Controller rollout, click Position, click Assign controller and double-click Path Constraint.