# 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.

2answers
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 ...
2answers
247 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 ...
1answer
181 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 ...
1answer
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 ...
1answer
1k views

### Opengl-es picking object

I saw a lot of picking code opengl-es, but nothing worked. Can someone give me what am I missing? My code is (from tutorials/forums) Vec3 far = Camera.getPosition(); Vec3 near = ...
1answer
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 , ...
1answer
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 ...
1answer
303 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 ...
1answer
231 views

### Drawing the same scene with perspective then orthographic projections

I have a scene that I'm rendering first with a perspective matrix. I then want to rerender it in a different viewport using an orthographic matrix for a top-down 2D view of the scene. I think I may be ...
1answer
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 ...
1answer
564 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 ...
1answer
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; ...
1answer
168 views

### Java moving image to where it is facing

I am trying to make an Asteroids type game. I searched and tried everything to move an image along its angle (as radiant). Using my knowledge of trigonometry I made the following calculation: x += ...
1answer
99 views

### Smooth Ramp to zonal harmonics

I have written in blitz3D some code to generate arbitrary 2D lighting lookup textures and I'm looking for a way to compress them. The idea is that they look rather smooth and low frequency, there must ...
1answer
171 views

### How to implement cue-stick animation for a pool game?

Hello I am developing a Pool game, and I've been scratching my head about what formula is needed to implement an animation for the cue stick. The animation of the cue stick should look as if it's ...
0answers
54 views

### PCF shadow shader math causing artifacts

For a while now I used PCSS for my shadow technique of choice until I discovered a type of percentage closer filtering. This method creates really smooth shadows and with hopes of improving ...
0answers
162 views

### Use quaterions to move the camera direction according to mouse movement

I am trying to use quaterions to move the camera direction vector in the following way. This code is perfectly working glm::quat temp1 = glm::normalize( glm::quat((GLfloat)( ...
0answers
132 views

### Display and Hide CCSprite with Genie effect

I am new at cocos2D. I started to learn cocos2D with simple game from http://www.raywenderlich.com/tutorials#cocos2d tutorial. Now I'm crazy with animation, so now i want to display CCSprite as OSX ...
0answers
100 views

### Stereo 3D: drawing 2D elements at apparent screen depth

I'm developing an application making use of DirectX11's stereoscopic features. At such I am not relying on nVidia's automatic implementation. That means I have to replicate a way to render 2d elements ...
0answers
65 views

### Surface normal to screen angle

I've been struggling to get this working. I simply wish to take a surface normal and convert it to a screen angle. As an example, assuming we're working with the highlighted surface on the sphere ...
0answers
119 views

### Quaternion to direction vector - flipping

I've kinda solved this myself by adapting the Camera::setDirection code from OGRE to work for my need: Now I have the following code: Vector3 boneDir = getBoneWorldOrientation(mEntity, mHips) * ...
0answers
464 views

### Catmull Rom Spline - Constant Speed

Given the equations found in the answer here: Determine arc-length of a Catmull-Rom spline How would one A) Apply this to a 3D Catmull-Rom Spline, and B) write A out programmatically (for the math ...
0answers
116 views

### Typical Applications of Linear System Solver in Game Developemnt

I am going to write a custom solver for linear system. I would like to survey the typical problems involved the linear system solving in games. So that I can custom optimization on these problems ...
0answers
169 views

### Portal View/Projection Matrix near plane

For RenderToTexture/Camera based portal rendering, the basics seems simple enough. However, with a free camera, most of the time it is going to be looking at such portals at an angle: Now a ...
0answers
43 views

### Rotating a joint to a desired angle

I would like to set the speed of my box2d revolute joint each update such that it will rotate to a desired angle and stop. My first thought was just to set the speed to +max or -max based on the ...
0answers
80 views

### How to aim with a spaceship in 3D considering its angular momentum?

So I have a spaceship and I have 6 degrees of freedom. At a given moment the following vectors are known of the spaceship: Local forward. Local up. Local sideways (may be implied from the previous ...
0answers
81 views

### Determining axis to rotate around

I'm trying to implement a free-look third person camera (using glm). I know that the general transformation is newCameraPosition = translate(lookatPoint) * rotation(angle,axis) * ...
0answers
136 views

### Rotate a point in 3D space with sine and cosine

I got my camera controlled by the mouse. Now I want a sphere to be always in the center of my view(just for testing). I tried that by assigning the sine of the Y rotation of the camera times 10 as the ...
0answers
167 views

### How do I implement a physics gun?

I'm currently trying to implement a physics gun for my game. What I want is for the entity to stay in the same position on the screen no matter how I wiggle the camera about, what is the correct way ...
0answers
143 views

### Issues with Spherical Coords and gluLookAt

I am currently developing a game set in a planet(A sphere), in which my camera mostly works though some issues arise from this method: ...
0answers
625 views

### Rotation deforming mesh (Opengl ES 2.0)

I'm trying to render a rotating cube on Opengl ES 2.0, using some math classes I wrote (based on a lot of online and offline info) for quaternions, matrixes and the like. As far as I know all the math ...
0answers
22 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 ...
0answers
83 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, ...
0answers
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 ...
0answers
38 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 ...
0answers
177 views

### JavaScript 3D space ship rotation

I am working with a fairly low-level JavaScript 3D API (not Three.js) which uses euler angles for rotation. In most cases, euler angles work quite well for doing things like aligning buildings, ...
0answers
27 views

### Is there a transformation or set of transformations that can approximate a “radial scale”?

Is there a way to, with matrices, scale something as if someone were opening a Japanese fan? I'm at a loss of what to call it, so pointers towards avenues of research would be greatly appreciated. If ...
0answers
176 views

### Space Strategy Ship Movement Math

This is similar to a question I asked a while ago, but I phrased it so terribly so might as well start over. I am trying to implement ship movement in 3D space, but confined to a 2D plane at y=0 (see ...
0answers
84 views

### Follow sinus with absolute value

I would like to make an arm follow the sinus of the ball. When I add an absolute value to the ball (on the y axis) to get a more realistic bounce, the ball is going 2 times faster. How could I ask ...
0answers
88 views

### Opengl 3.2 Flickering after smooth animation?

Okay I am new to OpenGL I am getting an odd issue. I am performing rotation on a bunch of triangles on a scene graph. The rotation starts off really smooth everything is animating then much later you ...
0answers
122 views

### How to predict encounters between a ship and a body's sphere of influence in 2D

Long time listener, first time caller. I'm making a little hobby game in XNA, its about transport ships in space, analogous to container ships at sea. There are to be AI ships and player controlled ...
0answers
130 views

### What is the connection between an isometric angle and scale

I am trying to work out an isometric projection matrix for a custom angle. In the engine I'm using there's a projection matrix defined like so: projection.rotate(45 * (Math.PI / 180) ); scale = ...
0answers
33 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 ...
0answers
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 ...