This is an Aftereffects tutorial about the Continuously-Rasterize/Collapsed-Transformations switch. Though practical, I do think that switch needs better PR and branding, since it's name is quite long :).
I just call it the sun button, though I've heard people call it the Gear button or the Star as well.
This switch is part of the switch board in the timeline panel, the second on the left . Right between the Kilroy / Shy switch and the Quality+Sampling switch. It has two functions:
continuously rasterize
When you scale a footage layer in the timeline beyond 100% it will get blurry and pixelated. If your source is vector, clicking on that switch will tell AfterEffects to keep it sharp, AfterEffects can treat that vector object as such. That is why it's called continuously rasterize, AfterEffects keeps rasterizing it ( converting to pixel image) at any scale.
You will notice that you cannot do that for pixel based footage (PSD, TIFF, png, jpg etc). There is no checkbox on these layers when you drop them in the timeline. If the image you bring in is vector-based - .Ai, .SWF, .SVG or .EPS then the feature is available. You can also do it on PDFs but only the vector objects within the PDF will get sharp.
Shape layers and type which was created in AfterEffects have that feature by default. The switch is turned on and grayed out. You cannot switch it off.
Collapse transformations
You can also turn that switch on for pre-composition layers. This allows you to access the features of inside a nested composition.
For example: if you have a composition that has a lot of 3-D layers, you might want to pre-comp them and use one 3-D layer with your camera and lighting. Once you pre-comp all the elements, you'll make that composition a 3-D layer. You will notice though, that your comp looks flat and that your camera has one flat object to move around, all the 3-D elements on the inside are flattened. If you hit that collapse transformations switch on that comp layer, now everything on the inside becomes 3-D.
Mind your Adjustment Layers
If you have an adjustment layer inside a pre-comp, and you hit that switch on the main comp, the adjustment layer will affect everything below that comp player as well. Basically when using that switch it's a bit like temporarily un-grouping a comp.