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Exploring continuous rasterization

From: After Effects Apprentice 08: Nesting and Precomposing

Video: Exploring continuous rasterization

In the past few movies, we've been focusing on the internal render order that After Effects uses when calculating each layer. Normally it's Masks, followed by Effects, followed by Transformations, and if you have it applied, followed by Layer Styles which happen last in this chain. You can not drag and reorder these processing steps, but you can use precompositions to divide up parts of the rendering task, for example, do an effect in a precomp, then move to a final comp and perform additional transformations and masking, et cetera. Understanding this render order goes a long ways towards demystifying what After Effects is doing when it creates a composite. However, After Effects does not always follow this rendering order and these exceptions are what we're going to focus on in the next few movies. We're still in the composition Render Order.aep. Close all compositions you may have opened previously, then open up the Comp > Render Example 3 > Rasterization. The biggest exception is something called Continuous Rasterization, and this only applies to some layers inside After Effects. Namely, layers that'd be constructed out of vectors, rather than pixels. Vectors mean outline or paths such as Illustrator artwork, but also apply to PDF files, SWF files, and even solids in After Effects. Those vector-based layers, like this Illustrator file here, have an optional check box where you can turn Continuous Rasterization on or off. Text and Shape Layers in After Effects are always continuously rasterized. You will see this check box turned on and you cannot turn it off. On the other hand, if you have a pixel-based layer like a video capture, a 3D render, et cetera, you'll see that you do not get a check box to continuously rasterize it. Pixels are pixels. They have already been created. The main point of vector layers is After Effects is taking those outlines of vectors then creating pixels from them, and that gives After Effects an additional step of flexibility in how it calculates those layers. I'm going to twirl up and twirl down this layer, and normally effects are followed by transforms. In this case, we have a Bevel Alpha and Drop Shadow effect followed by the Transform parameters, Scale and Rotation, which have been animated over the course of this composition. As I move my time marker through this comp, you notice a couple of strange things result from this particular rendering order. On the one hand, the fact that scale is performed after bevel and drop shadow, means the amount of bevel and the distance of the drop shadow are scaled up along with the rest of the layer, and this is a desirable end result. However, since rotation is also done after bevel and after drop shadow, you'll notice that the direction of the shadow and the direction of the bevel, these highlighted or shadowed edges, are also rotating as the layer is being rotated, and that is undesirable. A partial solution is just using continuous rasterization. For this layer, I'm going to enable this Continuous Rasterization switch. When I do that, Transforms actually take place before any other step. After Effects will apply all the transforms including Scale and Rotation, then convert the vectors into pixels, and after pixels have been created, then we'll apply effects, masks, and layer styles. One positive result of this is that your vector-based artwork stays sharp, regardless of what scale value you use. You notice that our scale value is over a 100%. When Continuous Rasterization was turned off, the text was looking a little bit soft and fuzzy. With the Continuous Rasterization on, the text is sharp, so that's a benefit. Secondly, since Rotation occurs before Bevel Alpha and Drop Shadow, having this switch enabled moves Transform before any other processing step. You'll notice that now the shadow direction and the bevel direction stay constant, that's because the layer has been rotated before those effects are being calculated. So this is another good thing. However, Scale is also being calculated before Bevel Alpha and Drop Shadow, and a problem with that is that the distance of the shadow and the size of the bevel are staying the same number of pixels. Those distances and sizes are not being scaled with the layer. The scale is occurring before these effects are being applied. And as a result, the shadow is unnaturally far away when the layer is scaled down, and the bevel is unnaturally large through here and gets smaller in relation to the layer size as the layer gets larger. Once you know these pluses and minuses, you can decide whether or not to enable Continuous Rasterization for a layer. In this case, we have two benefits; a sharper, less blurry looking layer, and our shadows and bevels constantly falling in the correct direction, and one negative, the scale not affecting the effects. We could use precomposing to help solve this by performing the scale in a later composition. However, there is another trick that very few After Effects artists know and that's called the Transform effect and that's what we'll demonstrate in the next movie.

Exploring continuous rasterization

In the past few movies, we've been focusing on the internal render order that After Effects uses when calculating each layer. Normally it's Masks, followed by Effects, followed by Transformations, and if you have it applied, followed by Layer Styles which happen last in this chain. You can not drag and reorder these processing steps, but you can use precompositions to divide up parts of the rendering task, for example, do an effect in a precomp, then move to a final comp and perform additional transformations and masking, et cetera. Understanding this render order goes a long ways towards demystifying what After Effects is doing when it creates a composite. However, After Effects does not always follow this rendering order and these exceptions are what we're going to focus on in the next few movies. We're still in the composition Render Order.aep. Close all compositions you may have opened previously, then open up the Comp > Render Example 3 > Rasterization. The biggest exception is something called Continuous Rasterization, and this only applies to some layers inside After Effects. Namely, layers that'd be constructed out of vectors, rather than pixels. Vectors mean outline or paths such as Illustrator artwork, but also apply to PDF files, SWF files, and even solids in After Effects. Those vector-based layers, like this Illustrator file here, have an optional check box where you can turn Continuous Rasterization on or off. Text and Shape Layers in After Effects are always continuously rasterized. You will see this check box turned on and you cannot turn it off. On the other hand, if you have a pixel-based layer like a video capture, a 3D render, et cetera, you'll see that you do not get a check box to continuously rasterize it. Pixels are pixels. They have already been created. The main point of vector layers is After Effects is taking those outlines of vectors then creating pixels from them, and that gives After Effects an additional step of flexibility in how it calculates those layers. I'm going to twirl up and twirl down this layer, and normally effects are followed by transforms. In this case, we have a Bevel Alpha and Drop Shadow effect followed by the Transform parameters, Scale and Rotation, which have been animated over the course of this composition. As I move my time marker through this comp, you notice a couple of strange things result from this particular rendering order. On the one hand, the fact that scale is performed after bevel and drop shadow, means the amount of bevel and the distance of the drop shadow are scaled up along with the rest of the layer, and this is a desirable end result. However, since rotation is also done after bevel and after drop shadow, you'll notice that the direction of the shadow and the direction of the bevel, these highlighted or shadowed edges, are also rotating as the layer is being rotated, and that is undesirable. A partial solution is just using continuous rasterization. For this layer, I'm going to enable this Continuous Rasterization switch. When I do that, Transforms actually take place before any other step. After Effects will apply all the transforms including Scale and Rotation, then convert the vectors into pixels, and after pixels have been created, then we'll apply effects, masks, and layer styles. One positive result of this is that your vector-based artwork stays sharp, regardless of what scale value you use. You notice that our scale value is over a 100%. When Continuous Rasterization was turned off, the text was looking a little bit soft and fuzzy. With the Continuous Rasterization on, the text is sharp, so that's a benefit. Secondly, since Rotation occurs before Bevel Alpha and Drop Shadow, having this switch enabled moves Transform before any other processing step. You'll notice that now the shadow direction and the bevel direction stay constant, that's because the layer has been rotated before those effects are being calculated. So this is another good thing. However, Scale is also being calculated before Bevel Alpha and Drop Shadow, and a problem with that is that the distance of the shadow and the size of the bevel are staying the same number of pixels. Those distances and sizes are not being scaled with the layer. The scale is occurring before these effects are being applied. And as a result, the shadow is unnaturally far away when the layer is scaled down, and the bevel is unnaturally large through here and gets smaller in relation to the layer size as the layer gets larger. Once you know these pluses and minuses, you can decide whether or not to enable Continuous Rasterization for a layer. In this case, we have two benefits; a sharper, less blurry looking layer, and our shadows and bevels constantly falling in the correct direction, and one negative, the scale not affecting the effects. We could use precomposing to help solve this by performing the scale in a later composition. However, there is another trick that very few After Effects artists know and that's called the Transform effect and that's what we'll demonstrate in the next movie.

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