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Creating a Circle With Code

Creating a Circle With Code

Jul 03 2018, 10:20 AM PST 5 min

Goal

This is not a Part with the shape of a ball. This is instead a rather hollow outline pixelated with many small bricks. In fact, you won’t be touching bricks at all – you will only be scripting.

Steps

  • Create a new, blank, map iRoblox Studio.

  • Insert > Object > Script

  • Insert the following into that script (the explanation is below):

for angle = 1, 360 do
	local p = Instance.new('Part', Workspace)
	p.Size = Vector3.new(1, 1, 1)
	p.Anchored = true
	p.CFrame = CFrame.new(0, 120, 0)                --Start at the center of the circle
	         * CFrame.Angles(math.rad(angle), 0, 0) --Rotate the brick
	         * CFrame.new(0, 0, 100)                --Move it out by 100 units
	wait()
end

Explanation

A circle has 360 degrees. You are going to create 360 little bricks for your circle. The “for” loop runs 360 times. The “math.rad(angle )” converts the angle, which is in degrees, into Articles/Using Radians to Measure Angles.

Each time the “for” loop runs, it:

  • Creates a new part, of which the parent is “game.Workspace”.
  • The part’s name is “Brick”
  • The Brick’s size is (1, 1, 1) – remember, we wanted little bricks.
  • All the bricks are anchored, so that they don’t fall down.

Now comes the tricky part: we want to position the bricks as a circle. If you’ve taken trigonometry, the next line should make sense. If not, all this is saying that the x value should be 100 times a mathematical function named “cosine” of the value of “i”, and the y value should be 100 times a mathematical function named “sine” of the value of “i”. Sine and cosine are functions to study angles and circles. The value of y is bumped up 120 squares, otherwise, it is mashed against the ground, which makes your circle look like a semicircle.

Now comes the tricky bit. Here we use CFrame composition, to avoid using trigonometry. We start off with a CFrame at the center of our circle. Then we rotate by the angle we need. Finally, we move the brick out from the center of the circle. Because this is applied after the rotation, the brick moves relative to the new orientation.

Run this, and you should get a nice little circle.

Advanced

The above example is a rather large circle. Let’s say you want a smaller one. You’ll have to do two things:

  • Reduce the distance you move out from the center of the circle
  • Reduce the number of iterations (which reduces the number of bricks).
for angle = 1, 360, 3 do
	local p = Instance.new('Part')
	p.Parent = Workspace
	p.Size = Vector3.new(1,1,1)
	p.Anchored = true
	p.CFrame = CFrame.new(0, 75, 0)        --Start at the center of the circle
	         * CFrame.Angles(math.rad(angle), 0, 0) --Rotate the brick
	         * CFrame.new(0, 0, 50)                 --Move it out by 50 units
	wait()
end

Ellipses

Ellipses are quite similar geometrically to circles. You just need to make one dimension (x or y) longer than the other:

for i = 1, 360, 2 do
	local theta = math.rad(i)
	local p = Instance.new('Part')
	p.Parent = Workspace
	p.Size = Vector3.new(1, 1, 1)
	p.Anchored = true
	p.Position = Vector3.new(100 * math.cos(theta), 0, 50 * math.sin(theta))
	wait()
end

Notice here that the x dimension is 100 *math.cos(i), and the y dimension is now only 50 *math.sin(i). You can swap these numbers to change whether the ellipse is longer horizontally or vertically. These numbers can also be changed to alter the length and width of your ellipse.

Tags:
  • scripting
  • procedural