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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
votes
2answers
983 views

Most efficient way to get the world position of the 8 vertexes of a Box Collider (C#)

What I am looking for is the most efficient way to get the world position of the 8 vertexes of the Box Collider of a freely rotated Gameobject. I cannot use collider.bounds since object is rotated, ...
1
vote
0answers
55 views

Detecting the two Vector3 that determine the bottom-edge of the side of a box-collider that had collision (with C#)

So, I understand that plenty of questions have been posted on how to detect which side of a Box Collider had collision. However, what I am trying to achieve is a little different. I want to find out, ...
1
vote
0answers
599 views

Calculating Minimum Translation Vector in Separating Axis Theorem based algorithm

In the 2D SAT collision determination algorithm, you project the convex polygons onto each potential separating axis. Supposing the polygons intersect, from what I understand, the axis for which the ...
0
votes
2answers
155 views

Optimal way to find point D that lays at the perpendicular line between point A and line BC

I am trying to write a script in C# to find the position of point D in 2D space in a specific scenario. I know the (X,Y) position of point A, which never happens to be on the line that contains the ...
1
vote
3answers
301 views

What's the most efficient way to find the position of a point in relation to corners of a rectangle despite rectangle's scale

I am struggling to achieve the following with C# (in Unity). I need to find the position of the points that lay at a given distance (let's say 1m) from the corners of a rectangle, in a way that the ...
4
votes
2answers
2k views

How to properly rotate towards a local point in Unity C#? (a local LookAt)

I am having a nightmare trying to make a child object rotate towards a given point of its parent object, similar to what is possible at the world level when using LookAt. The problem is that most ...
4
votes
1answer
248 views

Rotate perspective camera to align screen width to procedural object's width (Unity, C#)

I give up. After much trying and searching, I have to say I was unable to achieve the following task, for which I must call for your wise advice. In my current Unity 5 application (using C#), there ...
0
votes
0answers
131 views

Project 2d click/touch onto 3d plane

I have a 3d scene that contains an infinite plane that is NOT parallel to the camera (so every screen coordinate corresponds to a point on this plane- in other words, there are no possible invalid ...
11
votes
4answers
424 views

How do I interpolate around a rectangle?

I want to make a fancy animation where a point travels around a rectangle. I want to find the point's position at a time t. The rectangle is given by ...
3
votes
2answers
1k views

Calculate the slope of a 3D triangle?

I have lots of triangles in 3D space. How do I determine the slope/angle of these triangles with respect to a fixed ground plane? I need pseudo code examples at the very least.
1
vote
1answer
415 views

Sliding DOOM style collision resolution against arbitrary 2D geometry

I've been working on a HTML5 canvas raycasting engine for the web browser, with the end goal of making a simple FPS game in the style of the early 90s. The engine sits somewhere between Wolfenstein 3D ...
2
votes
2answers
553 views

Getting the topleft, topright, bottomleft and bottomright points of a shape in Unity3D?

I have a 4-point shape that is defined in screen space by the user. They can draw the 4 points, one at a time, in any order they wish. I am using a List of Vector2's to store the screen co-ordinates ...
0
votes
0answers
87 views

boost/geometry replacement in Java/for the JVM (Destructable Box2D terrain)

I'd like to reimplement https://github.com/seemk/DestructibleBox2D in Java. The main problem is finding an adequate replacement for the boost/geometry library. Any ideas?
0
votes
0answers
49 views

3D Picking: Doesn't Work Consistently

I'm trying to implement a 3D picking function that at the moment simply calculates the ray being sent from the camera after the user clicks the mouse on the window. It kind of works well when the ...
0
votes
2answers
165 views

Rotate coordinates back after rotating game context (geometry)

To achieve something similar to the image below using HTML5 canvas one can simply write the following: ...
2
votes
2answers
323 views

Detect collision that happen between frames, between slices of moving, rotating circles?

To detect a collision between two circles, we check if the distance between their centers is smaller than the sum of their radii. To detect a collision between a slice (in this case half) of a circle ...
-1
votes
1answer
415 views

Why is this unity camera moving in weird directions?

I have the following script ...
4
votes
2answers
904 views

How can I mask this CanvasRenderer?

I'm creating a text box that allows for selectable text, based off of Unity's InputField. An issue I am now facing is that the selection highlight does not respond to masks (The parent has a mask, but ...
2
votes
1answer
454 views

Does triangle-plane clipping in 3D always produce a triangle?

When you clip a triangle against a plane, will you always get a triangle out? Are there perhaps cases where you don't get a triangle out of clipping it against a plane?
0
votes
2answers
92 views

Calculate land center on grid

I have a grid based game. The main map is 2d array with land ids, something like this (here are 2 lands on the map, one formed where the 1's are and one formed by where the 2's are): [ 1 , 2 , 2 ] [ ...
0
votes
0answers
712 views

Taking a 2D slice of a 3D volume

I have a regular 3D polygon and I'd like to display 2D slices of it. What is the best way to achieve this? (Preferrably in OpenGL, but a general algorithm/tecnique would be good as well). I've ...
0
votes
1answer
220 views

Is there a way of moving the transform of an object relative to it's geometry

I have a number of objects (mostly prefabs) that have their transform origin in inconvienient places such as about 1 unit to the left of the actual geometry or somewhere inside an object where it's ...
1
vote
1answer
129 views

Ortho projection of 3D points with a vector

I have 3D points and I need to make an 2D orthographic projection of them onto a plane that is defined by the origin and a normal n. The meaning of this is ...
4
votes
1answer
357 views

Suboptimal A* Pathfinding Solution Example using Manhattan Distance Heuristic

I believe using an overestimating heuristic with A* is not guaranteed to find the shortest path. Assuming an agent can travel as a bird using euclidean distances, the manhattan distance provides just ...
36
votes
9answers
9k views

How can I quantify a drawn line's straightness?

I'm working on a game which requires players to draw a line from a point A(x1,y1) to the other point B(x2,y2) on the screen of an Android device. I want to find how well that drawing fits to a ...
1
vote
2answers
653 views

Outline of plane slice of arbitrary object

How would you extract the outline of a shape from slicing a plane through an arbitrary object? Note: This is related to my Unity Answers question, but not exactly the same.
0
votes
1answer
817 views

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 ...
2
votes
1answer
55 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 ...
3
votes
1answer
353 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 ...
0
votes
2answers
937 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 ...
0
votes
0answers
45 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 ...
0
votes
1answer
523 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 ...
0
votes
1answer
71 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.
0
votes
0answers
80 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. ...
0
votes
0answers
29 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 ...
12
votes
6answers
4k 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 ...
6
votes
5answers
8k 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 ...
1
vote
1answer
527 views

How to calculate reflection vector from point sprite sphere?

So far I achieved building a cube map following this tutorial. Then I drew three points using glDrawArrays(GL_POINTS,0,3) and calculate the normals based on a sphere. To compute the incoming light ...
4
votes
3answers
7k 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 ...
1
vote
0answers
223 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 ...
1
vote
1answer
68 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 ...
1
vote
1answer
777 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? ...
1
vote
1answer
590 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 ...
0
votes
1answer
1k 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 user-...
2
votes
1answer
235 views

Get quaternion between two objects on sphere

In a planetary gravity environment objects are represented in the following way: ...
2
votes
2answers
554 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?
2
votes
1answer
1k views

How do I calculate the distance between a point and a rotated rectangle?

This question is similar to another one about axis-aligned rectangles. However, I specifically want to calculate this for rotated rectangles. I have a rectangle with a (cx, cy) for the center point ...
1
vote
1answer
1k 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
votes
1answer
145 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 ...
0
votes
3answers
330 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 ...