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

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7
votes
3answers
3k 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 ...
2
votes
1answer
173 views

Finding the normals of an oriented bounding box?

Here is my problem. I'm working on the physics for my 2D game. All objects are oriented bounding boxes (OBB) based on the separate axis theorem. In order to do collision resolution, I need to be ...
18
votes
5answers
894 views

Moving CW or CCW?

Lets say we have a jagged shape: And two creatures moving along it's outline. Then we smooth the shape completely by pulling the corners out. We get this: It is easy to see now that Orange is ...
0
votes
1answer
2k views

“LNK2001: unresolved external symbol” when trying to build my program

I get the following error(s) on my program that captures the mouse and then draws a line. Errors: 1>------ Build started: Project: Capture_Mouse_Line, Configuration: Debug Win32 ------ 1> ...
4
votes
3answers
358 views

How to get distance from point to line with distinction between side of line?

I'm making a 2d racing game. I'm taking the nice standard approach of having a set of points defining the center of the track and detecting whether the car is off the track by detecting its distance ...
11
votes
2answers
3k 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 ...
10
votes
2answers
808 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 ...
1
vote
2answers
173 views

The distance to a line from a point, find the constant values?

I have 3 points, (x1, y1), (x2, y2), (x3, y3) I should find the AH height. For this i must use: How can i find each "a", "b" and "c" values?
1
vote
2answers
118 views

ricocheting off a wall

I have a capsule (sphere sweep) that I've computed the collision on a mesh with. I know the point of impact and normal of the face it collides with. My moving object - I'm using a capsule to ...
9
votes
1answer
4k 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 ...
0
votes
2answers
341 views

Partial recalculation of visibility on a 2D uniform grid

Problem Imagine that we have a 2D uniform grid of dimensions N x N. For this grid we have also pre-computed a visibility look-up table, e.g. with DDA, which answers the boolean query is cell X visible ...
1
vote
1answer
114 views

Intersection of player and mesh

I have a 3D scene, and a player that can move about in it. In a time-step the player can move from point A to point B. The player should follow the terrain height but slow going up cliffs and then ...
0
votes
1answer
160 views

moving in the wrong direction

Solution: To move a unit forward: forward = Quaternion(0,0,0,1) rotation.normalize() # ocassionally ... pos += ((rotation * forward) * rotation.conjugated()).xyz().normalized() * speed I think the ...
0
votes
1answer
56 views

applying rotation and speed to move user

My player has a position (vec3), rotation (quaternion) and speed. I have a fixed time step. At each tick, I work out from key-state etc what rotation and speed adjustments to make. How do I now ...
3
votes
3answers
1k views

Textureing subdivided Icosahedron in XNA, seam problem

*Look below for the updated source code* I have started to to make some different types of objects and create them by code in XNA. Right now I have finished the code for creating a Icosahedron. And ...
14
votes
4answers
634 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
467 views

Geometry vs sprites

I'm developing an android game, where the enemies are geometrical shapes. Performance is a main goal for me so I was wondering if defining shapes directly in OpenGL would be more efficient than using ...
1
vote
2answers
431 views

Separation of axis theorem implementation

I have been following the this guide to implement this. My current implementation is the following: class SAT { SAT(); bool collides(Rectangle rect1, Rectangle rect2){ var axises = [ ...
6
votes
2answers
466 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 ...
3
votes
3answers
505 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 ...
8
votes
2answers
3k views

How do I determine if one polygon completely contains another?

I have 2 polygons. I know the vertex coordinates of both polygons. What's the best way to check if one is completely inside the other? For example, the algorithm should only recognize the black ...
0
votes
1answer
1k 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 ...
0
votes
1answer
725 views

Easy way to project point onto triangle (or plane)

I have a mesh of triangles (navigation mesh), and a point in 3d space. This point should be "over" one of the triangles all the times. I'm trying to determine which triangle is the one the point is ...
1
vote
2answers
2k views

Render a polyline with rounded joints

I have a list of points (3D) and want to draw a line connecting all points with a specified width. The line should be rendered in OpenGL (using OSG) as triangles. The real challenge of this task is to ...
0
votes
1answer
237 views

Minimap Around Perimeter of Screen, Code Provided

What I'm essentially trying to do is what a lot of FPS's nowadays do in regards to their HUD. When an objective is off-screen, a small icon / symbol is shown on the perimeter of the screen, basically ...
7
votes
2answers
176 views

Intersect of vector and triangle side

I'm trying to create a triangular touch surface for iOS where the user can drag around a point inside this triangle. Using information from this page, it is easy to figure out if the dragged point is ...
4
votes
2answers
1k views

Repairing back-facing triangles without user input

My 3D application works with user-imported 3D models. Frequently, those models have a few vertices facing into the wrong direction. (For example, there is a 3D roof and a few triangles of that roof ...
1
vote
1answer
882 views

Using Actionscript 3's Graphics API in Flixel

My question sounds pretty simple but awfully, I couldn't find much information on the internet. How can I draw a circle in my FlxSprite? I couldn't find much information about drawing geometric ...
4
votes
2answers
479 views

Intersection points of plane set forming convex hull

Mostly looking for a nudge in the right direction here. Given a set of planes (defined as a normal and distance from origin) that form a convex hull, I would like to find the intersection points that ...
5
votes
1answer
918 views

How to perform simple collision detection?

Imagine two squares sitting side by side, both level with the ground like so: A simple way to detect if one is hitting the other is to compare the location of each side. They are touching if all of ...
2
votes
1answer
531 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 ...
0
votes
1answer
484 views

Calculate path of laser beam?

Lets say we have a laser beam emitter that has a position and an angle (in a 2D world to simplify things). The laser emitted from that emitter will start at that position, and continue heading in the ...
2
votes
1answer
359 views

High school-level geometry book focusing on game dev for struggling student?

Here's the situation. My brother, a freshman in high school, isn't doing too well in geometry. Partially because he doesn't do half the work, but partially because he seems to have genuine ...
1
vote
6answers
750 views

Testing whether two cubes are touching in space

Does anyone have any clean ideas on testing whether two cubes in 3D space touch? By touch I mean, touch at corners or on a face or on an edge. Say that the cubes are axis aligned and there is no ...
1
vote
0answers
293 views

How can I draw a model perpendicular to a sloped surface? [duplicate]

Possible Duplicate: How do I find rotation in 3D based on a vector/normal? My models are axis-aligned. I know the normal of the surface I want to draw them on. How do I compute the ...
6
votes
1answer
380 views

Running geometry shader only once

(Unfortunately couldn't find the answer myself) Does a neat way to cache the geometry shader results in Direct3D10 or OpenGL exist? (preferably Direct3D10). I'm building my geometry based on texture ...
29
votes
4answers
2k views

Why does my object move faster at 45 degrees than at 90 degrees?

I have objects in my game that move faster at 45 degrees then at 90 degrees. Each object has Point (x,y) position Vector2D (x,y) direction Int speed And what I do during a update is that new ...
4
votes
1answer
470 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
5answers
837 views

How would one determine the length of a path?

I have a game that requires each player to move along one specified path. I draw the path using Bézier curves. How can I determine the total real (not linear) length of the path and the distance that ...
1
vote
1answer
344 views

How do I determine if a tile is a slope based on the tile image?

In my game, every tile is a 32x32 texture. All the slopes are a 0 - 45 degree angle. I would like to determine, at the time I load the tile, if the is sloped by examining its texture/bitmap data. How ...
6
votes
2answers
216 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 ...
9
votes
2answers
326 views

How do you calculate if 2 lines are facing toward or away?

Given the 4 points describing 2 line segments, how do you calculate if line A is towards or away from line B? The 2 lines have a fixed length, and can be measured as distance from x1/y1 to x2/y2.
0
votes
0answers
94 views

Drawbacks for using only quads for model geometry [duplicate]

Possible Duplicate: Why do game engines convert models to triangles compared to keeping it as four side polygon What are the main drawbacks for using "only" quads for model geometry? Does ...
3
votes
1answer
2k 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 ...
7
votes
1answer
521 views

How can I determine the first visible tile in an isometric perspective?

I am trying to render the visible portion of a diamond-shaped isometric map. The "world" coordinate system is a 2D Cartesian system, with the coordinates increasing diagonally (in terms of the view ...
0
votes
2answers
550 views

Ways to define a curve

I'm trying to give shapes in my physics engine roundness/ curvature. I am aware of various methods for mathematically defining curves; such as bezier-cruves, ellipses, etc. However I am not sure ...
6
votes
1answer
10k views

How to calculate a 3x3 rotation matrix from 2 direction vectors?

I've got 2 direction vectors, for the X axis and the Y axis of the object. How do I calculate the rotation matrix of the object using these?
4
votes
2answers
543 views

OpenGL, Offset and Camera Space

I was reading chapter 4 of the Arcsyntesis OpenGL tutorial when I came across this line in the GLSL shader. vec4 cameraPos = position + vec4(offset.x, offset.y, 0.0, 0.0); About it, the tutorial ...
2
votes
1answer
708 views

Can Bullet Physics (or another 3d physics engine) use callbacks in my engine to check static geometry?

I'm wondering if it's possible to use or hack Bullet 3d Physics (or another free 3D physics engine) so that I don't need to "import" my static geometry into Bullet - instead I want to do it the other ...
7
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 = ...