1.2: Creating Expressions

Step 1

Now we are going to create expressions for the eyes.

Step 2

Create a new matrix for each eye and rename them:
rightPupilMatrix
leftPupilMatrix

Step 3

Select "rightPupilMatrix".
Select the "Offset" property.
Right-click and choose "Add Reference...".
Select "rightEyePoint" and choose the "Pos" property.
Click OK.
Watch rightPupilMatrix jump to the rightEyePoint position.
Do the same with "leftPupilMatrix" and add a reference to leftEyePoint.Pos.

Step 4

Select "rightPupilMatrix" again and right-click the "Offset" property.
Choose "Set expression like reference".
Do the same with "leftPupilMatrix".

Step 5

Move "rightPupil" inside "rightPupilMatrix" and
"leftPupil" inside "leftPupilMatrix".

Step 6

Hit F7 and drag the control points.
The pupils follow the control points.
We want the pupils to stay inside the eyes.

Step 7

Go back to design mode by hit F7.
Select "rightPupilMatrix".
Select the "Offset" property and open the code window.
Right-click and select the menu choice to copy the value of expression.
Replace the expression "Inside(rightEyePoint.Pos;" and paste (Ctrl+P) and then ";20)".
Click "OK" to update the expression.

Step 8

Close the code window and hit F7.
Drag the control point.
You will now see that the pupil doesn't move longer than 20 units from the center.
Repeat the previous step for "leftPupilMatrix".

Step 9

We have now constrained the eyes to look at the control points.