From Test-Scratch-Wiki
This is a tutorial on animating a three-dimensional object using the stack method.
Creating the Costumes
The first step in making an animated 3D object is to create the costumes. This is done by imagining one is slicing the object so that it is a stack of slices. For example, a cylinder, when sliced, would be a stack of circles. A cone would be a stack of circles with a decreasing diameter, and a sphere would be a stack of circles whose diameter first increases, then decreases. Each of these imaginary slices must then be drawn with a paint editor. For the sake of simplicity when programming, it is recommended that you have 16 slices.[citation needed]
Writing the Script
This project will require only one script and one sprite, thus it will be One Sprite One Script.
Theory
The script will draw the 3D object by Stamping each slice on top of the other, slightly displaced. This will cause the illusion of a 3D object by reconstructing the object which was "sliced" in the above section. The displacement will be determined by calculating the horizontal and vertical offset with a given angle, using trigonometry. The script will loop forever, slightly incrementing the angle each repetition to give the illusion of rotation. The drawing script must be Single Frame to prevent rendering lag.
Part 1: Setting up the stage
Firstly, the project must be set up. This includes:
The script is shown here:
when gf clicked forever go to x: (0) y: (0)//center sprite turn ccw (1) degrees//rotate sprite clear//clear stage change [angle v] by (1)//increment angle
Next, we must calculate the offsets using trigonometry:
when gf clicked forever go to x: (0) y: (0) turn ccw (1) degrees clear change [angle v] by (1) set [x-offset v] to ([sin v] of (angle))//x offset set [y-offset v] to ([cos v] of (angle))//y offset
Part 2: Moving and stamping
Next, the sprite must move and stamp itself, and change its costume accordingly. This is done with the following change:
when gf clicked forever go to x: (0) y: (0) turn ccw (1) degrees clear change [angle v] by (1) set [x-offset v] to ([sin v] of (angle)) set [y-offset v] to ([cos v] of (angle)) repeat (16)//repeat for each of the 16 slices change x by (x-offset)//move change y by (y-offset)//move stamp//stamp next costume//change costume end
However, when this runs, it is extremely slow. To speed it up, it is best to make the script Single Frame. The easiest way to do this is by using the duplicate function'. Right-click the top block of the script inside the repeat block (change x by), and select "duplicate". A copy of the script appears at your mouse. Drop this script right above the block you right-clicked. Now repeat this 3 more times.
 Note: | Each time, remember to right-click the new top block |
Finally, replace the "16" in the repeat block with 1:
when gf clicked forever go to x: (0) y: (0) turn ccw (1) degrees clear change [angle v] by (1) set [x-offset v] to ([sin v] of (angle)) set [y-offset v] to ([cos v] of (angle)) repeat (1) change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume change x by (x-offset) change y by (y-offset) stamp next costume end
Mouse 3D
This is how to make a 3D object follow the mouse adding a repeat block will make it easier
- Make the costumes (see Creating the Costumes)
- Add this script:
when gf clicked clear forever turn cw (3) degrees change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume change x by ((0.05) * (mouse x)) change y by ((0.05) * (mouse y)) stamp next costume
Another simpler technique is shown below:
when gf clicked clear forever clear change x by (2) stamp change x by (2) stamp change x by (2) stamp change x by (2) stamp change x by (2) stamp change x by (2) stamp change x by (2) stamp change x by (2) stamp change x by (2) stamp
This is another way of stacking slices on top of each other. This will not give you as satisfying results as the other technique shown above will. It will not create a very good 3D effect.
