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

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Rotate Object Towards Direction in 2D

For my RTS game's physics engine, I'm trying to find out a clever way to make a unit face the direction it's moving in. Given a Vector2d direction of movement (its normalized velocity), how can I ...
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1answer
14 views

Maya 2015 Collada mesh transforms not applied

I am trying to load a dae (Collada) model into my 3d engine. The problem is they export the vertices and transforms seperately. So in Maya 2015 it looks like this In the game engine I have it simply ...
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1answer
39 views

Mapping Coplanar Vertices in 3D space on to a 2D Plane

Say I have a plane specified by a normal vector and point on the plane. I want to specify a 2-D co-ordinate system that lies 'across' the plane, and then use that to find the 2-dimensional distance ...
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2answers
54 views

Moving OBB vs. triangle intersection test

Requirements: to write a test function that, given a moving OBB (oriented bounding box) and a triangle, returns true whenever the OBB hits the triangle. The OBB is described by its half extents (h1, ...
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23 views

Rotating between two coordinate frames

I have two coordinate frames, A and B. I want to create the rotation matrix RAB which takes you from A to B. A is a right-handed system, and B is a left-handed system. Furthermore, after moving from a ...
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1answer
69 views

Collision Detection algorithm using Line Detection

For a 2D physics sandbox I am working on, I need a way of detecting detecting a collision using lines. This sandbox uses a class called Particle, which has a x and a y (stored as a struct called ...
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1answer
64 views

How can i calculate that normal lays in same part of plane with point?

I.e. n0 for A and n1 for B. Plane divided by plane CD.
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0answers
40 views

Fat geometry shader

I've seen this video: all the geometry seems to grow and become fat. Nice effect. I'm just approaching the shader matter, and I'm still have to learn a lot about how to change geometry via shaders. ...
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0answers
21 views

How does collision detection work? [duplicate]

I was curious on how hit collision works in games. I know there is a simple method that gives every object in a 2D or 3D world a recengular hitbox that makes it easy to detect a collision, but when ...
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6answers
2k views

What's the fastest way checking if two moving AABBs intersect?

I have two AABBs that are moving, what's the fastest way to check if they will intersect under a frame? By moving I mean not just to check with the usual rectangle intersection method, I mean some ...
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5answers
2k views

How can I test whether points are within a polygon?

I have 2D-points, which boundaries depict a polygon. The points are at integer positions (no fractions possible). Now I want to build an enumerator in C# that returns all points that are inside the ...
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3answers
112 views

How do I interpret the dot product of non-normalized vectors?

I know that if you take the dot-product of two normalized vectors, you get the cosine of the angle between them. But if I take the dot-product of two non-normalized vectors (or one normalized, one ...
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34 views

How can I keep vertex order the same on every Instantiate()?

While trying to resolve another question, I have discovered that if I Instantiate() from a prefab, the order of the mesh vertices (and therefore triangles) is inconsistent between instances. This is ...
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1answer
50 views

Algorithm that cover one mesh by another mesh

Suppose I have two meshes (Let call me first MeshShirt and second - MeshBody) Meshes are aligned (if i render both MeshShirt "covers" MeshBody). But some parts of the body are not "under" the ...
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1answer
107 views

Formula to measure uv-mapping distortion

Does anyone know a simple way of calculating (offline) the amount a texture is distorted when mapped to a triangle like the following? Vertex Position UV Coordinates A (Ax, Ay, Az) ...
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1answer
83 views

Chamfered cube geometry generator

I'm trying to create a geometry generator for a "Chamfered Cube". I've got the vertices working, but I'm stuck with creating the faces. I don't really know how I could re-arrange my algorithm to ...
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0answers
48 views

Calculation technique for 2D inertia tensors?

Just wondering what the techniques are out there. It's only 2D so I figured there'd be a good chance for there to be a "one size fits all" solution out there that's essentially an analytical solution. ...
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1answer
89 views

Given seams, how do I unfold a mesh?

If a user marks a seam on a mesh, how do 3D modelling programs (like Blender or Maya) unfold the mesh on to a 2D surface? I can only find papers trying to automate the seaming for you. Given ...
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1answer
135 views

Get quaternion between two objects on sphere

In a planetary gravity environment objects are represented in the following way: struct object { struct quaternion quat; // quaternion to represent the rotation between the object and the center ...
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1answer
109 views

How to access Maya Bonus Tools 2012 in Maya 2014

I have been trying to use the paint geometry tool for Maya 2014 but it isnt showing up. I downloaded Bonus Tools 2012 and installed it. Where can I find this tool in Maya 2014?
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1answer
219 views

How to determine the distance between a point and a rotated rectangle

This question is very similar to How do I calculate distance from a point to a rectangle?. But that question assumes that the rectangle is axis-alligned, or not rotated. So just like in that ...
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1answer
193 views

In a TPS, how to aim bullets to the direction the camera is pointing, but make the shooting from the player?

(In C#/XNA.) I mean, I can't find an answer nowhere. I'm trying to learn how to make a Third Person Shooter, especially like the one I found in a game called "M.A.R.S.", from Epic Games. I don't want ...
2
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1answer
66 views

Distort a quad with a World Matrix

Is it possible to distort a quad multiplying its vertices by a specific world matrix? See the picture to understand what kind of distortion I need: Please note, that the quad is in 3d space and I ...
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3answers
52 views

Calculating the center of a turning circle

I'm trying to understand how to calculate the midpoint of a turning circle. In the attached picture, my unit is at location U. I want to compute the trajectory of the unit as it turns toward the ...
3
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1answer
114 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?
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1answer
92 views

How to calculate “real” distance between cursor and away 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 ...
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1answer
52 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.... int ...
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2answers
46 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 ...
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2answers
340 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 ...
8
votes
3answers
704 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#): public Vector3 ...
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1answer
28 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 do: I take three points from P, say a, b, c. Their centroid is denoted ...
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1answer
55 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 x', y', z' unit vectors that behave like origin of local coordinate system. x' and y' vectos should be on the plane ...
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1answer
72 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, ...
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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
102 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. ...
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2answers
125 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 ...
3
votes
1answer
365 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
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2answers
239 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
87 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
44 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 ...
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1answer
82 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 ...
1
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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 ...
8
votes
1answer
830 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 ...
1
vote
1answer
306 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 ...
3
votes
2answers
319 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
103 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
369 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 ...
1
vote
1answer
75 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
205 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
260 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 ...