EDIT (12 Mar 2012): Fixed ordering of groups in the example at the end. Thanks to Simon Jones for pointing out the error.
Understanding HitFilm’s rendering order will save you countless headaches and help you achieve your desired results much quicker than otherwise.
For clips on video tracks, their rendering order is bottom-up by track. Consider a timeline with 3 video tracks and some clips laid out as follows:
Video 3: [Explosion Composite Shot]
Video 2: [Bonfire Composite Shot]
Video 1: [My Movie][Another Movie]
The track rendering order is Video 1, then Video 2, then Video 3, and as each track is rendered the result is composited onto what was previously rendered and composited.
In the above example, at the playhead (Current Time Indicator) frame the rendering and compositing order is:
- Render ‘Another Movie’ frame
- Render ‘Bonfire Composite Shot’ frame, and composite it onto what was previously rendered (i.e. the Another Movie frame)
- Render ‘Explosion Composite Shot’ frame, and composite it onto what was previously rendered (i.e. the composite of Bonfire and Another Movie)
Composite Shot Timelines – 2D Layers
For 2D layers, the rendering and compositing order is the same as for clips and video tracks on the Editor timeline.
2D layers are rendered bottom-up according to their order in the list, and each layer is then composited onto the previous result. Consider a composite shot timeline with 3 layers:
1: New Grade [Grade]
2: New Plane 1 [Plane]
3: My movie [Media]
In this case, the media layer is rendered first, followed by the plane layer, and lastly by the grade layer. When each layer is rendered, it is composited onto the previous result.
Composite Shot Timelines – 3D Layers
3D layers are rendered and composited according to their transformation in 3D space. The order of the layer list doesn’t matter for 3D layers (except in one special case described below).
Using the above 2D layers example, let’s change all the layers to 3D and add a camera:
1: New Grade [Grade] [3D]
Position: (0, 0, 0)
2: New Plane 1 [Plane] [3D]
Position: (0, 0, -100)
3: My movie [Media] [3D]
Position: (0, 0, 200)
4: New Camera [Camera] [3D]
Position: (0, 0, 1200)
In this case, layer 3 will appear closest to the camera, followed by layer 1, and finally by layer 2, because of the order of their Z positions.
It’s not just the Z position that determines which layer appears closest to the camera, though. Two layers could have the same position in 3D space but have different orientations, causing them to intersect as in the following screenshot:
In this case, HitFilm subdivides the layers according to the intersection causing one part of the white layer to be composited in front of the green layer, and the other part behind it.
The special case mentioned above (where the order of layers in the layer list does actually matter for 3D layers) is when two or more layers are coplanar. That is, imagine two layers that not only have the same position in 3D space but also have the same orientation. In this case, there is nothing in the layers’ transformations that determines which should be in front of the other. So HitFilm chooses based on the order in the layer list. The top-most 3D layer will be rendered in front of the other coplanar layer.
2D and 3D Layers
A composite shot timeline can contain both 2D and 3D layers interleaved as the user desires. In cases like this, one or more 2D layers will divide the 3D layers into separate batches.
1: New Plane 1 [Plane] [3D]
2: New Plane 2 [Plane] [3D]
3: New Grade [Grade]
4: New Plane 3 [Plane] [3D]
5: New Plane 4 [Plane] [3D]
6: Camera 1 [Camera] [3D]
In the above example, the 2D grade layer divides the scene into two separate 3D batches. Within each batch the 3D layers are rendered according to their transformation in 3D space, just as described earlier.
But layers in the first batch (planes 1 and 2) and layers in the second batch (planes 3 and 4) cannot intersect each other.
In addition, the first batch (planes 1 and 2) will always appear on top of the second batch.
Some of this can be difficult to grasp without experimentation and seeing the results visually. Try it for yourself and the rules will soon become clear.
A 2D layer will divide 3D layers into separate batches even if the 2D layer’s visibility switch is set to hide the layer. That is to say, the existence of a 2D layer in the list, regardless of any of its switches or settings, is all that is needed to divide 3D layers. You need to remove the 2D layer from the list (or change its order) if you don’t want to separate the 3D content.
Effects and Masks
In general, the rendering order is top-down whenever you see a list or tree of objects. For example, when you expand a layer you’ll usually see these groups:
This means that masks are rendered first, then effects, and then finally the layer is transformed (e.g. rotated or scaled).
Likewise, when you see a list of masks or a list of effects within a group, those objects are rendered in top-down order too. Consider a layer with three effects:
Brightness & Contrast
This means that the Brightness & Contrast effect is rendered first, followed by the Blur, and then lastly Reflection.
Text and Grade Layers
It’s worth noting that Text and Grade layers have a different ordering of Masks, Effects and Transform than other layer types. Their order is:
Again, the top-down rule applies. But in these cases, the masks and effects will be applied after the layer has been transformed.
Changing the Order
So, it’s reasonable to ask, what happens if you want an effect to be applied before a mask? Or a layer to be rotated (transformed) before applying a horizontal blur effect (assuming the Transform group comes after Effects)?
The answer to all these types of problems is: nested composite shots.
By moving a layer into its own composite shot you can apply some operation(s) to the layer inside that composite shot, and then separately apply other operation(s) to that composite shot layer.
For example, here’s how to rotate the layer before applying a Blur:
Main Composite Shot
1: My Movie Comp [Composite Shot]
My Movie Comp
1: My Movie.mp4 [Media]
Check out the reference manual for more information on nested (or embedded) composite shots and the handy Make Composite feature.
For more on 2D and 3D compositing and transformations, I recommend watching these great video tutorials: