[Darby Edelen]

You might get the result you want simply by switching the continuously rasterize switch on for the solid layer and using the scale property. This will scale the layer and masks before the stroke effect is rendered as opposed to after.

Darby Edelen

[Darby Edelen]

Here’s a sample that uses the active camera and tests the layer the expression is applied to:


c = thisComp.activeCamera;
p = toWorld(anchorPoint);
cp = c.fromWorld(p);
if(cp[2] <= 0) behindCam = true;
else behindCam = false;


Darby Edelen

[Darby Edelen]

Here’s a result from my Z820. This machine is pretty well equipped, although you can see that I didn’t go for the fastest CPUs available. I wanted to stick with air cooling and I was trying to keep the price tag around $10k (I already had the GPU).

Darby Edelen

[Darby Edelen]

[Eric Chard] “Sadly, this did not work. In 3D terms I need the ‘world coordinates’ of the null, not the keyframed coords, since they just sit at 0/0/0.”

This would give you the world coordinates of a layer named “Null” in your composition:


l = thisComp.layer("Null");
l.toWorld(l.anchorPoint);


[Eric Chard] “Since I imagine this will require expressions, I disremember how you can build an expression library so I don’t have to type/remember this technique– how is that done?”

There is some simple reference available for expressions if you use the fly-out menu from the expression box. This helps to explore the methods available for various object types but may not help if you’re not already familiar with expressions.

Alternatively you can create an Animation Preset of the expression using Animation > Save Animation Preset… You’ll likely need to adjust the expression when applying the preset to new properties/new layers in new contexts.

Darby Edelen

[Darby Edelen]

Sometimes there’s another way around the problem. Can you describe the strange reason you can’t use scale?

Darby Edelen

[Darby Edelen]

The sampleImage() function returns a color as a 4-component vector in this form: [red, green, blue, alpha]. The ranges of the values are 0-1. You can convert these to Hue/Saturation/Lightness values and then sample just the lightness like this (I’m including some variables that stand in for things like the “point” and “radius” for the sampleImage function):


c = sampleImage(point, radius);
lum = rgbToHsl(c)[2];


The [2] component of the HSL version of the color is the lightness. Also, it’s important to note that the “point” variable is not a composition or world point, but one in the layer’s local space.

Once you have that value you can use it with a linear() or ease() function to remap the 0-1 range to another range, here’s an example for scale:


linear(lum, 0, 1, [50,50], [150,150]);


Which would vary scale from 50% to 150% on X and Y axes for a 2D layer as the brightness of the layer being sampled goes from 0 (black) to 1 (white).

I’m not covering all the details of implementation, so if you’re new to expressions/JavaScript you’ll likely have lots of additional learning to do in order to make this happen.

Also, if you are going to use an easily defined shape like a circle, ellipse, box or rectangle then I wouldn’t use sampleImage() but rather use code to drive the expression. It would evaluate much faster.

Darby Edelen

[Darby Edelen]

I’ve seen this happen when the 3D Null moves behind the camera. In those cases I usually check to see if the 3D Null is behind the camera and if it is I move the result of the expression to an arbitrary off-screen location like [-3000,-3000].

That’s a general idea that may work in a few different circumstances.

Darby Edelen

[Darby Edelen]

If the polygons belong to different objects I think you’ll need to select those objects and use Mesh > Conversion > Connect Objects before you Optimize the resulting mesh.

I very often use Connect and Delete as I don’t normally need the separate objects any longer. If you just use Connect then the separate objects will still exist and you’ll have a new object that contains all selected objects as polygon groups.

Either way the new Connected object can be Optimized.

Darby Edelen

[Darby Edelen]

I generally use Optical but I don’t really mind one way or another what the default is.

Darby Edelen

[Darby Edelen]

The only feature that benefits directly from an NVIDIA GPU is the ray-tracing renderer.

I’d recommend not getting too attached to the idea of buying the new Mac Pro until you see impartial performance benchmarks and pricing information. I suspect that this model is going to set a new high mark on Apple’s price/performance wall of shame.

Darby Edelen