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

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85 views

Point in Polygon, Ray Method: ending infinite line

Having a bit of trouble with point in polygon collision detection using the ray method i.e. http://en.wikipedia.org/wiki/Point_in_polygon My problem is I need to give an end to the infinite line ...
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1answer
50 views

Geometry design and buffers

I'm making some tests with rendering stuff and I'm wondering how to design my Geometry class. For the moment, here is how I do: Init: Stock array with positions, array with colors, array with ...
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2answers
127 views

which quarter of a triangle the point is in

I've got a world made out of squares. The square are devided in four triangles like this: The corners have their heights stored in a 2D array and the center height is the average of the corners. To ...
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2answers
244 views

How to make a projectile align correctly with the entity that shot it

I'm developing a 2D game. In the game, all entities can rotate 360 degrees. Each entity holds an angle value, and every frame it is drawn rotated around it's center by it's current angle value. For ...
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1answer
375 views

Explain this line segment intersection code

I've been reading this article on pathfinding over polygon meshes using line-of-sight, and in the article are several code snippets. One of them, the one I'm trying to understand, is a simple function ...
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1answer
91 views

XY Location scaling with varying density screens

I have a phone with resolution H=1280,W=720,Density=2 I have a tablet with resolution H=1216,W=800,Density=1.331 I drew a rectangle on my phone with corners Left,Top (-1.6,1.55), Right,Bottom ...
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0answers
45 views

Equation / formula to determine an objects position on an ellipitcal path

I'm making a space game, as such I need objects to follow an elliptical path (orbit). I've worked out how to calculate all the important aspects of my orbits, the only remaining thing is how to have ...
8
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1answer
885 views

Tessellation vs Geometry Shader

Correct me if I'm wrong, but both the Geometry Shader and the Tessellation Shader jobs are to generate vertices in the Graphic Pipeline. What I would like to know is how they are different and when ...
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1answer
75 views

Reflection velocity

I'm trying to get a moving circular object to bounce (elastically) off of an immovable circular object. Am I doing this right? (The results look right, but I hate to trust that alone, and I can't ...
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4answers
2k views

Is there a 3D equivalent of hex tile maps?

Probably the biggest advantage of a hex-based versus square-based map tiling is that the center of each hex has the same distance to all its neighboring hexes. Is there a similar shape that tiles this ...
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1answer
272 views

How do you make a bullet ricochet off a vertical wall?

First things first. I am using C# with XNA. My game is top-down and the player can shoot bullets. I've managed to get the bullets to ricochet correctly off horizontal walls. Yet, despite using similar ...
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1answer
327 views

Sphere-Sphere intersection and Circle-Sphere intersection

I have code for circle-circle intersection. But I need to expand it to 3-D. How do I calculate: Radius and center of the intersection circle of two spheres Points of the intersection of a sphere ...
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2answers
320 views

Find the next cell in a grid from a point and direction

I'm trying to solve a very simple problem but I'm unable to come-up with an efficient solution so far. What I'm really trying to do is voxelize triangles in a three dimensional environment but I'll ...
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2answers
104 views

Connecting two arbitrary points with 2 lines

DEFINITIONS: Any "Point (x, y)" mentioned below is really the bottom left coordinates of a 1 unit by 1 unit rectangle. A "Line" is a defined as a rectangle that is either 1 unit tall and 1 unit or ...
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3answers
374 views

Throwing a ball and estimating its path using a Physics engine

The problem: A player entity wishes to throw a ball from a known position with a known initial velocity. The surrounding environment contains physical objects that can alter the trajectory of the ...
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4answers
453 views

How can I find the largest sphere that fits inside a frustum?

How do you find the largest sphere that you can draw in perspective? Viewed from the top, it'd be this: Added: on the frustum on the right, I've marked four points I think we know something about. ...
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1answer
77 views

Calculate diameter of sphere large enough to encompasss a frustum

I'm attempting to speed up box-to-box collision checks by first testing if two spheres large enough to encompass each (respectively) would collide (because I'm using separating axis theorem and it's ...
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2answers
219 views

Find closest point from an origin, in a mesh

I want to do something similar to a raycast. With a raycast, you can set an origin and a destiny, and check where the ray collides with something but only with a line. What I want to do, is given an ...
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1answer
391 views

Converting between Spiral Honeycomb Mosaic and axial hex coordinates

There seems to be quite a lot of logic in dealing with hexagonal grids using a system of axial coordinates like the one described here. In doing some reading about hex grids, though, I ran across the ...
2
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1answer
283 views

Moving an object toward another object on sphere knowing their quaternions

I have a sphere centered in world origin. On the sphere surface I have two objects and I know their quaternions (rotation around sphere). Currently my movement works on Vector2 inputs (cannot change ...
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2answers
102 views

How can I test if a point is behind a polygon in 2D?

In order to improve the performance of my visibility graph generator I am trying to figure out the following. Given the image below; is there a way to find out if a point is 'behind' the polygon? For ...
8
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1answer
1k views

How can I project a 3D point onto a 3D line?

Let's say I have a line defined by two points, A and B, both in the form (x, y, z). These points represent a line in 3D space. I also have a point P, defined in the same format, that isn't on the ...
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0answers
61 views

Rasterizing euclidean planes

I'd like to visualize a BSP tree. To do this, I need to project an arbitrary euclidean plane onto a projection plane. I was thinking about calculating the intersections of the plane with the viewing ...
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1answer
692 views

How do I make a curved surface out of rectangular blocks?

For a Peggle-like game, I want to make blocks that follow a curve, like this: The blocks would then disappear as the ball hits them. I managed to draw some horizontally, but I'm having trouble ...
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1answer
52 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 ...
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49 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 ...
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2answers
166 views

Calculate shadow map to overlay hidden line-of-sight things in 2d?

Given a 2D sideview with even-sized grid squares and our hero in a known center-ish position like this ... and imagining this hero's line of sight like this... how could one get the point values ...
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2answers
961 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 ...
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1answer
569 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 ...
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1answer
2k 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: ...
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2answers
2k views

How do I use the dot product to get an angle between two vectors?

I am learning to use normalized vectors in my games. I've learned that in order to know the angle between two vectors, I can use the dot product. This gives me a value between -1 and 1, where 1 ...
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3answers
1k views

How to move an object along a vector

Let's say I got an object A and object B in a 2D game. I create a vector leading from A to B. It's name is AB. How can I make A move along the vector AB and reach B? One way I was thinking of doing ...
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3answers
634 views

Are the first three values that describe a 3D plane actually a 3D vector?

A 3d plane is typically defined as a,b,c,d. Are a,b,c actually the x,y,z coordinates of a 3d vector, with d defining the rotation of the plane, something like axis-angle rotation data?
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1answer
171 views

map the section of a procedurally generated surface on a plane

I'll try to be as clearer as I can. I have a surface on a 3D space which is not flat, it has hills and depths. My goal would be intersect it with a plane so that I can map the section of the surface ...
2
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1answer
177 views

How do I compute the point of a triangle-ray intersection?

I have a line (the direction vector of the player) and a triangle representing the face of a model (so composed of 3 points). I can't find the mathematical operation to check if that vector is ...
2
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1answer
620 views

2d grappling hook for platformer?

What are the options and mechanics for creating a grappling hook in a 2D game? In the prototype for this feature, the person runs around in a platformer world and can throw the hook at any wall, ...
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2answers
118 views

How can I compute the movement of an object along a parabola?

I am working on a simple 2D game. In the game, I have a 'robot' that throws a ball towards another robot, in the shape of a parabola. Both 'robots' have the same Y coordinate. The program knows the ...
0
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1answer
88 views

How to modify normal vectors with a tranformation matrix

Transformation is quite simple when it comes to Position or Color of the vertex, for Position just multiply matrix * vector and for color just don't do anything, but my question now is: How to handle ...
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2answers
205 views

Using Geometric Slerp to move Camera

I'm writing a program in C++ using OpenGL and GLM; I'm trying to get my camera to follow my car. So far it successfully follows it around the screen, but I'm having trouble adjusting the Camera's ...
4
votes
3answers
3k views

How can I draw a quad in wireframe with modern OpenGL, without rendering the interior bisecting edge?

I want to draw a quad (not two triangles). I actually know that triangles are faster, as I answered this question. But let's say I am building a 3D modeling tool. It makes sense to draw a quad for ...
0
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3answers
3k views

Spherical coordinate from cartesian coordinate

I am implementing a type for Ogre 3D rendering engine to provide spherical coordinates. So far everything is working fine, until I try to build spherical coordinates from a cartesian vector. Here is ...
4
votes
2answers
519 views

Allowing a player to walk up and down slopes without resistance

I am trying to implement a platformer where both the player and the level are made up of arbitary polygons. One requirement is that the player can stand still on slopes, and walk up and down them ...
7
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2answers
1k 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 ...
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1answer
511 views

How to generate AABB, OBB & Sphere from polygon soup

How can I generate AABB, OOBB and Sphere from a polygon soup, where the bounding volumes are defined as follows: AABB should be specified by min(x,y,z) max(x,y,z) OOBB should be specified by ...
5
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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 ...
0
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1answer
132 views

“Walking” along a rotating surface in LimeJS

I'm trying to have a character walk along a plank (a long, thin rectangle) that works like a seesaw, being rotated around a central point by box2d physics (falling objects). I want the left and right ...
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1answer
92 views

How can I find a position between 4 vertices in a fragment shader?

I'm creating a shader with SharpDX (DirectX11 in C#) that takes a segment (2 points) from the output of a Vertex Shader and then passes them to a Geometry Shader, which converts this line into a ...
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2answers
357 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 ...
2
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1answer
187 views

Why is there high performance hit with many meshes?

I am currently reading upon Geometry Instancing, as I want to render a lot of animatable objects on the screen. However I have come to a more fundamental question first: Why do I even need to use it? ...
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2answers
4k 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 ...