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

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177 views

A controlled trapezoid transformation with perspective projecton

I'm trying to implement a controlled trapezoid transformation in Adobe Flash's ActionScript using the built-in perspective projection facility. To give you an idea of how the effect looks like: ...
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2answers
436 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 = [ ...
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1answer
2k views

what algorithms exist for combining multiple triangle meshes into one mesh

Let's say I have a terrain mesh of some triangles, and several smaller meshes which I want to add to that terrain mesh (think ground and some small mounds or berms for example). What would I look for ...
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2answers
2k views

Voronoi regions of a (convex) polygon

I'm looking to add circle-polygon collisions to my Separating Axis Theorem collision detection. The metanet software tutorial (http://www.metanetsoftware.com/technique/tutorialA.html#section3) on ...
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1answer
286 views

Frenet frame and application

I have just been reviewing Frenet Frame math. It is an interesting geometrical issue. I know that common applications are: camera movement along a curve tube and ribbons surface Can someone ...
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1answer
81 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 ...
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1answer
48 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 basically looking at the points from the top ...
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0answers
54 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
103 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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1answer
609 views

Geometry shader and triangle adjacency

I'm currently trying to change my project to use GL_TRIANGLE_ADJACENCY instead of GL_TRIANGLES. Following this question, I have managed to construct my index buffer fine, but when it comes to the ...
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0answers
58 views

Blender: calculation of elevation and rotation angle from plane

I have a generic plane (any location, any rotation around every axis) with its normal axis passing by the center. Then I have a generic point and I need to find the elevation and the rotation angle ...
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3answers
194 views

Geometry problem for area of sight

My player have a line of sight and all objects between the white lines, turns red. To compute this, the following conditions are met: if the angle between the yellow line and the red line are small ...
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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 ...
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1answer
353 views

enemy View Range , chase player

for 3D: Q1 : I want to make zone range for each enemy in the game , so that when the player in the view range he will be chased . Q2 :if I want to make enemy walk a little bit around his position ...
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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 ...
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1answer
429 views

Issues with Sine Wave Generation and Rotation

I'm working on generating objects in sine wave that lets you specify parameters that are start x, end x, start y, and end y position. Below is the method that I used to generate the debris void ...
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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 ...
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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 ...
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1answer
819 views

Rotation of Rectangle along Y-axis transformed to parallelogram

After the rotation of a rectangular view along the Y-axis, about its center, transformed into parallelogram, how do I get the rotated parallelogram coordinates? By Y-axis, I mean perpendicular to the ...
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2answers
551 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 ...
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1answer
163 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 ...
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1answer
336 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
52 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
142 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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1answer
106 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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1answer
136 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
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 ...
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2answers
607 views

ray polygon intersection

Hi, I am looking for an elegant way to do ray and polygon intersections in 2d. I don't care about languages. Now what I'm doing is taking a line that lies on the ray (with a screen length) and ...
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1answer
488 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 ...
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2answers
51 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 ] [ ...
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2answers
104 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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1answer
66 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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1answer
152 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
101 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
58 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
59 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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1answer
50 views

How to linearly blend between multiple points, deviating from a default point?

I have a set of 3D points that I need to "blend" between. Lets say I have points [A,B,C] and I have the amount I want to blend each as [0.5, 0.2, 0.8], how can I blend between these points with the ...
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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> ...
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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 ...
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1answer
238 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 ...
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2answers
343 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 ...
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1answer
317 views

How do I rotate a segment + normal so that the normal is (0,-1) and the segment is now axis aligned

I have an arbitrary line segment, which may or may not be axis aligned along with its normal eg: Segment(Coord(-1,-1), Coord(1,1), Coord(-1, 1).normalize) which represents a line segment with a 45 ...
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3answers
306 views

exact point on a rotating sphere

I have a sphere that represents the Earth textured with real pictures. It's rotating around the x axis, and when user click down it has to show me the exact place he clicked on. For example if he ...
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0answers
18 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?
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0answers
32 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 ...
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1answer
19 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: var TO_RADIANS = 0.0174532925; context.translate(30, 20); context.rotate(30 * TO_RADIANS); ...
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0answers
18 views

Making a node map with PNG alpha channels

I currently creating a 2d game that requires the usage of boats that travel from one country to another. The countries are individual objects with there own png. Nehow I've got the original map of the ...
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0answers
69 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 ...
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1answer
59 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 ...
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1answer
76 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.