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Mathematics questions deal with the arithmetic, geometry, calculus, formulae and other calculations used in the development of a game.

1 vote
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Get all points of a parabola

In general, there is no parabola that goes through three given points. However, if you loosen the problem constraints and only define the Y coordinate of the parabola’s top and allow its X coordinate …
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1 vote
Accepted

How do I find the largest circle possible in a square of pixels using Unity?

On a 40×40 square of pixels, you can draw a circle with approximately 40×sqrt(8) pixels. If you are looking for a circle drawing algorithm to let you pick the pixels to put in your array, an easy way …
sam hocevar's user avatar
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6 votes

What is a simple algorithm for calculating evenly distributed points on an ellipse?

Reasonable approximation As already stated in other answers, there is no exact way to do this. However, it is possible to efficiently approximate a solution. My formula will only handle the upper ri …
sam hocevar's user avatar
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1 vote

How to draw a line of a given length towards a given object?

You do not need the angle itself, just the direction, which is given by vector End - Start. For convenience it's good to normalise that vector, ie. divide it by its length. You will then extrapolate o …
sam hocevar's user avatar
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1 vote
Accepted

Finding the angle of a line given 2 other lines

All you need is atan2: angle = atan2(frontwheel.y - rearwheel.y, frontwheel.x - rearwheel.x);
sam hocevar's user avatar
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9 votes
Accepted

Understanding log/exp formula for RPG experience

When used together with exp, the log function is commonly understood as the natural logarithm. You are actually using base 10 logarithm (which would be log10 in C++). Fortunately you can get the same …
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6 votes
Accepted

How to draw equal length line stripes on a parabola?

The derivative of the ball position is: dx/dt = vx dy/dt = vy + gravity * t So the derivative of the parabola arc length s is, using Pythagora’s theorem: ds/dt = sqrt(vx² + (vy + gravity * t)²) …
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4 votes
Accepted

Adding tolerance to a point in polygon test

Since the algorithm already parses all edges of the polygon to see how many times a ray cast from test crosses them, I think it's reasonable to add a check to see whether test lies on the edge exactly …
sam hocevar's user avatar
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38 votes
Accepted

Formula for three competing heroes, each has one they can beat and one they're beaten by

Your game is a nontransitive game. You can implement it with 3 stats R, P and S, using the rock-paper-scissors logic. Call these stats whatever you want, but I'll stick with the RPS logic. Now suppos …
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1 vote

Compute cone angle (cos) given side and hypotenuse vectors at time 0 and world matrix at time 1

Despite its name, Vector3.Transform() does not transform a vector but a point. The unwanted side effect is that the translation part gets added to your vector. If you want to actually transform a vect …
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1 vote
Accepted

Affine transformation: rotate a plane parallel to another plane

I need a way of translating a set of points P I suppose you mean rotating here? Let Z = (0,0,1). If cross(N,Z) has length 0, it means that all your points already lie in the desired plane. Other …
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3 votes

Usage of math.Atan2 in a 3D coordinate system with Unity

Beware of the argument order here. Here is what atan2 will give you: atan2(x,z) is the angle between the (x,0,z) vector and the +Z axis in the Z-X plane. atan2(z,x) is the angle between the (x,0,z) …
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0 votes

calculating the weights for direction vectors to a target

The distance between the centre of the circle (x1,y1) and the target (x2,y2) is: D = sqrt((x1-x2)² + (y1-y2)²) So the distance between the target and any point on the circle varies between D - r an …
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2 votes
Accepted

Why does Mathf.Log(x) return infinity in this case?

Here is a more numerically stable (for large values) way of getting Log(Fn) where Fn is the nth Fibonacci number. Let φ = (1 + sqrt(5)) / 2 and ψ = (1 - sqrt(5)) / 2. Then the nth Fibonacci number is: …
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5 votes
Accepted

Tangent to a circle through a point

Let b be the angle between vectors p1p2 and p1p3. Its value can be computed as: b = pi - atan2(p1p3.y, p1p3.x) The angle between p1p4 and p1p3 is b-a. Since p1p3p4 is a right-angled triangle, we kn …
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