# Tagged Questions

Arithmetic, geometry, calculus, and all else which resolves the number-crunching necessary in a game. Math questions are those that deal with the formulae and calculations used by the game in various parts.

67 views

### Algorithm for randomly generating reachable platforms

I want to randomly generate reachable platforms on the fly for a 2D game. Right now, I am just creating platforms at random x,y positions. Only 4 platforms can exist at once, so once the 5th one is ...
26 views

### TEMPLE RUN Trigonometric Formulas used [on hold]

What are the formulas used in developing TEMPLE RUN?? i just need it for my research project thank you ASAP
44 views

### How can I fix my sprite being rotated 90 degrees more than toward the mouse?

I am trying to get a Sprite in LibGDX to look at the player's mouse. Here's the code I have (mind you, I am using JRuby): target = mouse_position.sub(spatial.position) rotation = ...
323 views

### Modify random distribution functions :: Make it less likely to get multiple similar values in a sequence

I want to generate a sequence of numbers for procedurally generating planets in a galaxy sector. Each planet should be placed randomly, however it should be very unlikely that two planets are directly ...
34 views

### Segment-Segment continuous collision detection

I'm implementing a continuous collision detection system and need to check if the edges of two triangles will collide. One segment is stationary, while the other moves with constant velocity. The ...
1k views

### Orthographic Camera Zooming

In XNA I am using a spritebatch to render a board. I have created a camera class which can provide me a view and projection matrix. Currently I am supplying the view matrix to my sprite batch when I ...
602 views

### rotate opengl mesh relative to camera

I have a cube in opengl. It's position is determined by multiplying it's specific model matrix, the view matrix, and the projection matrix and then passing that to the shader as per this tutorial ...
24 views

### Projecting a Quad from light source and Normal Vector

I'm having a decal mesh( a quad) which has a shadow texture. and I have a bike, which has its forward direction, I have the normal to the ground, and normal touching point to ground. I have also the ...
36 views

### Getting the position of a directional light w.r.t. a moving object.

I have a forward vector of my object, which is a bike, and its position, and I have a directional light direction. I would like to know where the light is with regards to the bike ...
79 views

### Calculating How To Intercept a Moving Object [duplicate]

So I have two objects, Target and Interceptor. Target's position, direction of movement and movement speed are known, and Interceptor's position and movement speed are also known. Both movement speeds ...
1k views

### Bezier curve arc length

How can I find the distance traveled by a Bezier curve? For example, the distance traveled by a Linear Bezier Curve is: distance = sqrt(pow(x[1] - x[0], 2) + pow(y[1] - y[0], 2)); But what about ...
33 views

### Best method for selecting points from a point set - path distance

having a big set of points and a polygonal path what is the best way to select a set of points that are at a certain distance or smaller from the path? Or do I need to iterate thru all points on each ...
297 views

### Algorithm to zoom a plotted function

I'm making a game in android and I need plot a function, my algorithm is this: @Override protected void onDraw(Canvas canvas) { float e = 0.5f; //from -x axis to +x evaluate ...
58 views

### Perspective projection computation

I'm learning OpenGL from arcsynthesis and I don't understand something about perspective projection (http://www.arcsynthesis.org/gltut/Positioning/Tut04%20Perspective%20Projection.html). When the ...
237 views

### Constrained/penalized distance function

Assume a character is located on a n by n grid and has to reach a certain entry on that grid. Its current position is (x1,y1). Also on the same grid is an enemy with coordinates (x2,y2). Each step ...
61 views

### How can make an object orbit a sphere in a random direction?

How can I move an object on a random orbital path around a sphere? I've created some objects at an initial position that is essentially a random point on the sphere offset by some distance (say, ...
157 views

### Square Grid Polygonal Terrain Query algorithm?

I have a square, fixed-grid terrain with one terrain type per grid unit in my game, and I want to do an arbitrary polygonal terrain query which returns all of the grid units enclosed/intersected by ...
228 views

### How can I center a circle around a point on an HTML canvas?

I've got a job to make an engine and light game for canvas in HTML5. I like the things I make to be centered on the x,y positions I give it, I don't know why, it just helps me think about them ...
182 views

### Are there multiple valid definitions for what translate, rotate and scale do?

Are there multiple valid definitions for what translate, rotate and scale do to the 4x4 matrix? I bring up this question, because I have a simple webgl program that draws a square and does a few ...
42 views

### Java Angle Math: Calculate how near the player looks to an entity [duplicate]

I am programming a Minecraft Bukkit plugin and need a way to calculate an input number from 0 to 360 for displaying a custom compass / radar. So if the player directly looks at the object (shouldn't ...
246 views

### Need help with a complex 3d scene (using Ogre and bullet)

In my setup there is a box with a hole on one side, and a freely movable "stick" (or bar, tube). This stick can be inserted/moved through the hole into the box. This hole is exactly as wide as the ...
248 views

### Rotate around the centre of the screen

I want my camera to rotate around the centre of screen and I'm not sure how to achieve that. I have a rotation in the camera but I'm not sure what its rotating around. (I think it might be rotating ...
70 views

### matrix to rotate a vector to a known arbitrary axis

Let's say I have a vector V (v.x,v.y,v.z) which is normalized and points somewhere in 3d space. And that I have another vector Z of (0,0,1). Knowing only these two things I'm looking for a ...
84 views

### Alter a model-view-projection matrix

I have a model-view-projection matrix created based upon my camera. Is it possible to make alterations to it after it was computed to affect the corners of the resulting camera frustrum? For example, ...
304 views

### How can I remove the view and projection matrix from ray position to get only the ray model?

I've got a little problem with my picking module and I need your help. I have a method to project a ray from the camera to a fixed point when I click somewhere. The computed ray looks good, it go to ...
87 views

### What are the correct angles in the Top-down perspective?

In the following picture it says that in the Top-down perspective the angles are 90°, but if it would be 90° then you shouldn't see the front of the building and the roof at the same time... So what ...
171 views

### Transforms in Box2D

I'm attempting to implement a camera in my game. I had it working for regular objects, but I began using Box2D and obviously things changed a bit. I have a Body object that I want to draw at the ...
129 views

### How do I avoid interpolation artefacts when scaling up a heightmap?

I am using a bicubic interpolation algorithm in order to upscale a height map, and I am noticing some artifacts around the pixels boundaries. However, these artifacts don't seem to appear when I use a ...
58 views

### Trying to make sprite float up and down [closed]

Using LibGDX + Box2D and my understanding of the answer posted from this question: Here I apply the following impulse: // modify sprite's Box2d Body object int a = 8; // amplitude int f = 1; // ...
2k views

### How do I calculate rotation caused by bounce friction?

Following on from my previous question: I have the ball quite realistically bouncing from surfaces it hits. Now I'd like to make it spin from the friction of the hit. Showing this is simple enough: I ...
565 views

### LibGDX Perspective Camera for 2D

I'm very new to LibGDX and I'm trying to use DecalBatch with PerspectiveCamera, simply to have z-coordinate for my sprites, as SpriteBatch does not offer that. However, I don't know how to calculate ...
334 views

### Forcing one projectile to follow close behind an initial projectile

I'm shooting out a projectile and I want another projectile to closely follow it. I can't simply shoot out the second projectile at a slightly lesser time because the first projectile may change ...
174 views

### Camera lookAt target changes when rotating parent node

have the following issue.I have a camera with lookAt method which works fine.I have a parent node to which I parent the camera.If I rotate the parent node while keeping the camera lookAt the target , ...
31 views

### Comparing lerping quaternion

2d top down game. I want my transform to first rotate and face the target position and then move towards it. I got the rotation towards the target position done. It works great. But i need a way to ...
36 views

### lerp z rotation towards mousepointer

I am trying to get transform.rotation.z to chase the mouse pointer at a rotation speed. But I get a very weird results and can't figure out what I am doing wrong. var mp = Input.mousePosition; ...
67 views

### Lerp speed or lerp time [closed]

Am I right about the fact that lerping can be done over a set period of time or at a speed which will continue until the target is reached? How are the formulas for the two? Is it something like ...
49 views

### How to convert bones skeleton into joints skeleton?

I'm exploring skeletal animation and taking Half-Life SMD format as example. It has skeleton rigged as hierarchy of joints. Each joint has a parent and offset + rotation to it. Now I'm importing ...
70 views

### Area of surface contained in pixel

Let's say I have some surface rasterized and stored to a texture. How do I calculate the actual surface area that is visible in one of the rasterized pixels, from some other location? So far, I'm ...
426 views

### Can I jump from A to B?

I'm making some rudimentary AI for my side-scroller and I need to know whether an AI unit can reach point B from point A simply by taking a jump. Flight trajectory of my characters is a bit unusal as ...
344 views

### Canting of track in a racing game

I am trying to create a small racing game in which the track would be modeled using a BSpline curve for the path's center line and directional vectors to define the canting of the track at each point. ...
41 views

### Implementing ClearPath (crowd pathfinding)

This is the academic article: http://gamma.cs.unc.edu/CA/ClearPath.pdf Here is the confusing part (marked in red): The first part is the path in which the object will move. The first part of ...
40 views

### Calculating Friction due to rotation from ball bounce? [duplicate]

In this question asked by codemonkey, The rotation will depend upon: upon impact, on: Initial Speed of the ball hitting the surface (magnitude of ball velocity vector) Friction co-efficient of ball ...
266 views

### RK4, Derivatives, Understanding Game Physics

Gafferon Games has a great article on RK4 Integration for building physics simulations which can be found here: Integration Basics Personally my mathematics and physics knowledge could use ...
85 views

### How can I properly rotate a 2D vector in the “flipped” XNA client space?

In my 2d XNA game, because SpriteBatch treats world space as client space and has positive Y axis down and negative up, I've built my game's world space with that coordinate system too. However, I've ...
68 views

### Convert atan2 value to standard 360-degree-system value [duplicate]

Lets say I'm using atan2 to get the angle between two vectors. atan2 gives a value in radians. I convert it to degrees using a built in function in Java. This gives me a value between 0 and 180 ...
59 views

### How does atan2 work when getting angle of a vector?

I know that atan2 gives me the absolute angle of any vector. But it doesn't give a value from 0 to 360 degrees. Instead, it gives a value (if I'm not mistaken), between 0 and 180, or between 0 and ...
66 views

### How to adjust a font to fit inside a speech bubble?

I'm creating a game that contains a speech bubble for dialog. The idea of this function is to allow one call to set new text in a speech bubble. The speech bubble will adjust in size of the new font ...
88 views

### Using atan2 to calculate angle between two vectors

I understand that: atan2(vector.y, vector.x) = the angle between the vector and the X axis. But I wanted to know how to get the angle between two vectors using atan2. So I came across this solution: ...