How to Use 3D Coordinate System in Adobe After Effects 7

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Video Transcript

Now this point you should be understanding how to rotate and move elements manually in 3D space, and let us take a look at doing more numerically in the timeline understanding After Effects 3D coordinate system in the process. We are just going to hit the tilda key again to go back down to our workspace layout and let us come over the project pane now, and choose composition 2 that is simply called grids.

Double click to open that and we will see a simple graphic showing us currently the X axis and the Y axis. Now we are going to start chopping and changing between different views at this point in time, so it is worth learning a few very, very handy shortcuts. Again we are currently looking through the active camera. This will be the rendering camera.

If we look at the options here we do have access to the front, the left, the top, the back, the right and the bottom view. These are all straight views. So if we choose the front axis here, we will not see any perspective. There is no camera that governs this particular view. We simply look at all the objects flat and face on. Same as if we come in from the left hand side, we can see the different layers represented here. This will become very clear in a second when we switch to 3D, but remember that these are all two dimensional views of our scene.

However, if we come down to custom view 1 as you have seen before, we can see more of a 3D layer. Now active camera, the front view and custom view 1 all have keyboard shortcuts applied and they are very easy to remember. If we hit F10 on the keyboard that will take us to our front view, F11 changes us to our custom view 1 and F12 takes us all the way back to the active camera.

So currently let us hit F10 to go to the front view, hover the cursor over here and hit the tilda key to go full screen. Now just as in the side here, if you are hitting F10, F11 and F12 on the Mac and you are seeing very strange things happen to all of your windows on screen that is because expose has its keyboard shortcuts set to use exactly those three keys. So you will need to go into your system preferences and adjust those if you want to make full use of having these three shortcuts in After Effects.

And to tell you the truth, these are certainly much more important especially considering the amount of 3D work we will be doing in this series. Now in the previous series, the essentials one, I did talk about something called the Cartisian Coordinate System. Now this is a system designed by a man called Rene DeCartes that gives us a point in two dimensional space.

Now that system is measured from the upper left hand side of the composition and this is exactly how After Effects works. 00 is in the upper left and the X axis goes across. You can see that represented by our graph here. The Y axis is vertical which we should know now from the 3D rotation we have already played around with, but the plus and minus you are seeing here is also very important.

The X axis measures plus from the left hand side out to the right hand side, and negative value on the X will take us out of the composition and into the paste board area here on the left. However the Y axis actually measures zero at the top and the negative value actually goes higher than that. A positive value on the Y axis in 3D space actually measures downwards.

So this can be slightly confusing because you are probably used to an item that moves up increases in value. Well in After Effects, it is the other way around. Now if we hit the F11 key that will switch us to our custom view. We can now also see the Z axis. Remember that the X is going across here. The Y is coming down the center of the screen. The Z axis is the one that is going away from the camera and towards the camera.

Roughly, when we look at the active camera, we are sitting round about here and looking at this scene head on. If we hit F12, you can see just that. We are looking straight at the front of all of those elements. F11 to go back to the custom view for just one second and we will see where the Casrtisian system can become a little bit confusing.

We already understand that the measurement system works from the upper left hand side and outwards. However, in 3D space you would expect that anyone of these layers if we go ahead and select the yellow X and Y axes here, it does give us a center point which is right in the middle of our scene.

Well in the 3D world that should be 0, 0, 0 on X, Y and Z but this is not the case. If we hit the tilda key for one second so we can see our timeline, I currently have layer 4 active just to make it easy to understand. Let us click on source name and go to layer name and we are indeed looking at the X, Y graphic. If we hit the P key to get the position value, all of a sudden we are seeing something very weird, 400, 400 and 0 so it is telling us that the X axis is 400 pixels, the Y axis is the same and the Z axis is zero.

Well this is actually the one that is correct. The Cartisian system is based on X and Y but After Effects 3D space does make sure the Z axis from the dead center of the 3D world. So at zero an object is in the middle of the scene, but the reason that the other two dimensions are showing up down here at 400 and 400 is purely based on the size of the composition itself.

The composition is measured from the upper left, now down to his center point. And even if we are in a two dimensional composition, it would work the same way. If you remember that any other solid that you may have selected before, when you hit the P key and look at its position, it may show something like 360x270 because that is half of the size of the 720x540 square pixel composition that is measured to its center point.

Well the 3D system is working exactly the same way. If we hit control K or command K on the Mac to bring out the composition settings for this particular comp, you will see its size is actually 800 pixels square. Have that to 400x400 and this is exactly what we are getting here. The center of this comp is 400 on the X, 400 on the Y, but 0 on the Z. Now once you understand that concept and realize that every 3D layer works exactly the same way and this value will also change depending on the size of your composition, then you can start to position things very accurately inside 3D space.

I will admit, it does take some getting used to because you are familiar with the upper left concept 00 in 2D, but do remember it also applies in 3D. Now just to illustrate this point in other way, if we look at the bottom of the scene you will see the soft edge blue shape, this is actually a floor solid that has been added to the scene. A mask ahs been drawn around the overall shape and it has a feathered edge just to blend it into the background. So it is not like we are using any lights here. This is simply cheating the effect.

Now if we come down to the bottom of our timeline, we can see that the very bottom layer here is the axis floor. And if we select that and hit the P key, we can check its actual position. So the 400 value is its X axis so it is centered horizontally on the scene. The 0 value is the Z axis so again it is vertically centered on the scene, but the 1500 value here is the Y axis. This is how farther floor is down in 3D space.

Now 1500 does not mean that it is 1500 pixels from the center of the scene all the way down. Remember, from 0 at the top here to the center of this particular comp is 400 pixels, that means with a 1500 pixels total value, take 400 off of that, the actual 3D world position of this floor is 1100 pixels from center point down. So bearing that in mind you can easily position things in direct relation to each other mathematically just understanding that you have to use that offset size of the composition.