A branch of mathematics concerned with questions of shape, size, relative position of figures, and the properties of space.

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10
votes
2answers
8k views

converting a mouse click to a ray

I have a perspective projection. When the user clicks on the screen, I want to compute the ray between the near and far planes that projects from the mouse point, so I can do some ray intersection ...
10
votes
2answers
1k views

Arbitrary Rotation about a Sphere

I'm coding a mechanic which allows a user to move around the surface of a sphere. The position on the sphere is currently stored as theta and phi, where theta is the angle between the z-axis and the ...
6
votes
3answers
2k views

2D isometric: screen to tile coordinates

I'm writing an isometric 2D game and I'm having difficulty figuring precisely on which tile the cursor is. Here's a drawing: where xs and ys are screen coordinates (pixels), xt and yt are tile ...
4
votes
1answer
3k views

How do I find rotation in 3D based on a vector/normal?

I've been playing with Blender and Python, doing basic things like accessing vertices/normals,etc. I can get the normal of each face of a mesh. I was wondering, how can I get the rotation of a face ...
14
votes
3answers
5k views

How do you programmatically generate a sphere?

Could someone please explain how it would be possible to create a sphere vertices, indices and texture coordinates? There is a surprising lack of documentation on how to do so and it is something that ...
9
votes
1answer
3k views

Circle-Line Collision Detection Problem

I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line ...
4
votes
1answer
354 views

rotating an object from sourceAngle to destAngle, both 0-359, clockwise or counter clockwise?

I've got a game object i need to rotate. It's current angle is player.rotation, the destination is targetAngle, both in degress, 0 to 359. I've got a function named rotateDirection(float sourceAngle, ...
10
votes
2answers
516 views

How to limit click'n'drag movement to an area?

I apologize for the somewhat generic title. I'm really don't have much clue about how to accomplish what I'm trying to do, which is making it harder even to research a possible solution. I'm trying ...
4
votes
1answer
2k views

Morph a sphere to a cube and a cube to a sphere with GLSL

I'm getting started with GLSL with quartz composer. I have a patch with a particle system in which each particle is mapped into a sphere with a blend value. With blend=0 particles are in random ...
6
votes
2answers
324 views

Robust line of sight test on the inside of a polygon with tolerance

Foreword This is a followup to this question and the main problem I'm trying to solve. My current solution is an hack which involves inflating the polygon, and doing most calculations on the inflated ...
2
votes
1answer
1k views

Generating spherical world from heightmapped terrain

I am using a standard heightmapped procedural terrain in my project. However, I want the terrain to appear spherical when the user zooms out. This is an attempt to simulate the appearance of a ...
0
votes
2answers
804 views

How to determine the point of intersection of two lines? [closed]

I have two lines say P1( 0, -1, 0, -1 ) and P2( -1, 0, 0, -1 ). Since I'm working in 2D, there is no Z component. The x,y,z components are normals and the w component is the distance from origin. I am ...
-2
votes
1answer
82 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 ...
22
votes
4answers
2k views

Is the Manhattan distance monotonic when used as heuristic function?

I have a square-based map. Only horizontal and vertical movement is allowed (no diagonals). Movement cost is always 1. I'm implementing an A* algorithm on that map, using the Manhattan distance as a ...
14
votes
4answers
544 views

Algorithm for creating adjacent triangles

I have a system where you can click once to place a node in a scene. When you place 3 nodes, it forms a triangle. When you place any future nodes, it creates a new triangle by joining that node to the ...
4
votes
2answers
263 views

a flexible data structure for geometries

What data structure would you use to represent meshes that are to be altered (e.g. adding or removing new faces, vertices and edges), and that have to be "studied" in different ways (e.g. finding all ...
24
votes
1answer
1k views

How do you turn a cube into a sphere?

I'm trying to make a quad sphere based on an article, which shows results like this: I can generate a cube correctly: But when I convert all the points according to this formula (from the page ...
7
votes
2answers
1k views

Geometry System of Populous: The Beginning

I want to to develop a game like Populous: The Beginning with my friend. But we could not find out what type of geometry they have used for the world. We know that - all tiles have the same size - ...
7
votes
2answers
465 views

How does Unity3D lower an imported .obj vertex count?

I have a question regarding how Unity3D handles importing of .obj files. I'm importing this teapot: http://groups.csail.mit.edu/graphics/classes/6.837/F03/models/teapot.obj The number of vertices ...
7
votes
5answers
764 views

How do I calculate distance from a point to a rectangle?

I have a 2D rectangle with x, y position, height and width, and a randomly positioned point nearby. Is there a way to check if this point might collide with the rectangle if it is closer than a ...
6
votes
2answers
190 views

How do you calculate if a line is facing a curve?

Given the 2 points describing a line segment, and the 3 points describing a quadratic bezier curve, how do you calculate if the line is facing towards or away from the curve? The line has a fixed ...
5
votes
2answers
2k views

How do I align the matrix used in SpriteBatch and the matrix used in BasicEffect?

I'm writing a Windows tool that uses XNA and allows the user to place textures on the screen. I'm using a 'camera' for the SpriteBatch used to draw the textures, e.g: Matrix matrixForSpriteBatch = ...
2
votes
1answer
332 views

How do I make a low pass filter (average of readings over time) for compass?

I'm making a prototype for android that pulls compass data from the phone. I want to stabilize it so it is less jerky, by taking the average of the last couple of readings. I have done this for ...
5
votes
1answer
124 views

trapped inside a Graph : Find paths along edges that do not cross any edges

This is a graph based platformer level and the round shapes are creatures. I am looking for a path traveling along edges that does not cross other edges(To simulate the creature crawling on the ...
5
votes
2answers
1k views

Generating geometry when using VBO

Currently I am working on a project in which I generate geometry based on the players movement. A glorified very long trail, composed of quads. I am doing this by storing a STD::Vector, and removing ...
3
votes
3answers
342 views

Adding tolerance to a point in polygon test

I've been using this method which was taken from Game Coding Complete to detect whether a point is inside of a polygon. It works in almost every case, but is failing on a few edge cases, and I can't ...
1
vote
1answer
90 views

How to linearly “blend” between multiple 3D points?

I have a set of 3D points that I need to "blend" between. Lets say I have points [A,B,C] and I have the amount I want to blend each as [0.5, 0.2, 0.8], how can I blend between these points with the ...
0
votes
1answer
531 views

Determining and culling non-visible vertices

Ahoy! After posting my previous question on tile maps, i've been tinkering with an implementation i'm rather pleased with so far but would like to gather some more information about submitting ...
-5
votes
3answers
298 views

in the shadow of a sphere [duplicate]

(Related, but somewhat different, to my previous question) How can I determine in a fragment shader if a fragment is in the shadow of a sphere? That is, if it is occluded by the sphere and is past ...