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Questions tagged [geometry]

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

3
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1answer
163 views

How can I animate characters' static-geometry eyes?

Here's a Nintendo example: Specifically, the animation of the pupils seems not to animate the geometry. How is this done?
0
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2answers
152 views

How to calculate “real” distance between cursor and distant object?

I don't really know how to formulate the title, but the problem is the following: I'm using a scripting language called "SQF" which has been created by a company named "Bohemia Interactive" (no, I do ...
1
vote
1answer
115 views

Rotating a square rendered on a Bitmap

I'm writing a Software Renderer for fun/learning. Basically, it's just a giant array of integers which contain hexadecimal values (representing colour) that are rendered to the screen.... ...
2
votes
2answers
61 views

Calculating angle a segment forms with a ray

I am given a point C and a ray r starting there. I know the coordinates (xc, yc) of the point C and the angle theta the ray r forms with the horizontal, theta in (-pi, pi]. I am also given another ...
3
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2answers
425 views

How to calculate direction from initial point and another point?

I'm making a simple game where I shoot things from a certain point on screen (A). I tap the screen and shoot the projectile from initial point(A) to the tap point(B). But I want the projectile to ...
10
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3answers
4k views

How do I translate a spherical coordinate to a Cartesian one?

Could someone point me in the right direction as to how this might be achieved? 3D math / geometry often throws me. I'm looking for something like this (ideally in C#): ...
1
vote
1answer
35 views

Error in plane transformation

I have a bunch of coplanar points, who sit on plane P. I want to translate the plane to Q with the points upon. Here is what I ...
0
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1answer
89 views

Picking a local origin as the centroid of given three points in 3D

Given three points non-collinear P, Q, R in 3D, I need a generic method to generate ...
1
vote
1answer
180 views

How do I combine matrix transformation with non-uniform screen scaling in Flash?

I'm using a Flash transformation matrix for affine transformation. I have a rectangular image being rotated and scaled (in 2D). There are two sets of scaling variables, ScreenScaleX and ScreenScaleY, ...
0
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1answer
73 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 normals,...
1
vote
2answers
306 views

How to find the points of intersection of two OBBs

In my game I need to be able to find the points of intersection between two OBBs. I'm using Separate Axis Theorem to check if there's an intersection and get the penetration vector if there is one. ...
0
votes
2answers
318 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 ...
4
votes
1answer
854 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 ...
3
votes
2answers
395 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 ...
2
votes
1answer
567 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 (1.6,-1....
3
votes
2answers
491 views

Calculate laser bounce inside polygon

I am trying to calculate the reflection of a laser within a polygon. My current calculations are probably quite long-winded because I'm building on line intersection and other functions. The problem ...
1
vote
1answer
129 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 ...
2
votes
1answer
291 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 ...
10
votes
1answer
4k 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 ...
5
votes
1answer
6k 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 and ...
3
votes
2answers
443 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 ...
2
votes
2answers
393 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 ...
3
votes
3answers
542 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 ball....
1
vote
1answer
135 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 ...
0
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3answers
322 views

How to find the total bounds rectangle around a list of rectangles

How can I find the total bounds rectangle around a list of rectangles? Rectangle object: a simple data structure of 4 floats (w,h,x,y). I have an array of 2 or more rectangles and want to create a ...
1
vote
2answers
1k 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 ...
1
vote
1answer
767 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 ...
3
votes
2answers
25k views

How do I add an image inside a rectangle or a circle in JavaFX?

Suppose we have a rectangle called r Rectangle r = new Rectangle(40, 20); and an image called image ...
2
votes
2answers
248 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 ...
17
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2answers
18k 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 ...
0
votes
0answers
68 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 ...
7
votes
1answer
2k 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 ...
0
votes
1answer
159 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 ...
0
votes
0answers
53 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 ...
12
votes
1answer
2k 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 ...
1
vote
2answers
391 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 ...
-2
votes
2answers
7k 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 ...
1
vote
4answers
8k 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 ...
2
votes
1answer
9k 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 ...
4
votes
3answers
10k 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 <...
14
votes
2answers
23k 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 ...
2
votes
1answer
293 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
votes
1answer
446 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
votes
1answer
1k 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, ...
1
vote
2answers
351 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
votes
1answer
788 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 ...
-1
votes
2answers
402 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 ...
4
votes
3answers
9k 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 ...
2
votes
3answers
7k 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 ...
3
votes
3answers
415 views

Divide rectangular image into fixed number of random sized rectangles + 1 fixed size rectangle

I'm trying to divide a rectangular image into a fixed number of smaller rectangular image parts (of random but bounded width / height), with the exception of 1 rectangle which is predefined in ...