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

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2answers
47 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 ...
2
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2answers
109 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 ...
2
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1answer
174 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
171 views

Finding the normals of an oriented bounding box?

Here is my problem. I'm working on the physics for my 2D game. All objects are oriented bounding boxes (OBB) based on the separate axis theorem. In order to do collision resolution, I need to be ...
2
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1answer
47 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 ...
2
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1answer
146 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 ...
2
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1answer
70 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 ...
2
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2answers
106 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 ...
2
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2answers
103 views

Decomposing a collision grid into a set of boxes

I'm looking for a decent algorithm to decompose a collision grid (e.g. bool[w,h])... ...into a non-overlapping set of boxes (e.g. List<Rectangle>). The solution does not have to be the ...
2
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1answer
838 views

How to calculate collision normal between two AxisAlignedBox's?

I'm writing a physics simulation in Ogre3D and I'm trying to figure out how to calculate the collision normal between two Ogre::AxisAlignedBox's. I am checking for collisions using the "intersects" ...
2
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2answers
138 views

Splitting Graph into distinct polygons in O(E) complexity

If you have seen my last question: trapped inside a Graph : Find paths along edges that do not cross any edges How do you split an entire graph into distinct shapes 'trapped' inside the graph(like ...
2
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1answer
1k views

How do I determine the collision normal in an axis aligned bounding box collision?

I have a 3d moving box and a stationary box. I can detect collisions ok but now I would like to slide the moving box against the stationary box as a collision response. For this I need the normal of ...
2
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0answers
231 views

How to trace contour of shapes with holes?

I am experimenting with the RVO2 library for collision avoidance in a 2D simulation. This library supports specifying arbitrary obstacles as a list of vertices. The obstacles must be full shapes, i.e. ...
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2answers
170 views

The distance to a line from a point, find the constant values?

I have 3 points, (x1, y1), (x2, y2), (x3, y3) I should find the AH height. For this i must use: How can i find each "a", "b" and "c" values?
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1answer
868 views

Using Actionscript 3's Graphics API in Flixel

My question sounds pretty simple but awfully, I couldn't find much information on the internet. How can I draw a circle in my FlxSprite? I couldn't find much information about drawing geometric ...
1
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1answer
85 views

Which Graphics/Geometry abstraction to choose?

I've been thinking about the design for a browser app on the HTML5 canvas that simulates a 2D robot zooming around, sensing the world around it. I decided to do this from scratch just for fun. I need ...
1
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3answers
191 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
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1answer
116 views

How to linearly “blend” between multiple 3D points?

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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6answers
709 views

Testing whether two cubes are touching in space

Does anyone have any clean ideas on testing whether two cubes in 3D space touch? By touch I mean, touch at corners or on a face or on an edge. Say that the cubes are axis aligned and there is no ...
1
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2answers
245 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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2answers
177 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 ...
1
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1answer
113 views

Intersection of player and mesh

I have a 3D scene, and a player that can move about in it. In a time-step the player can move from point A to point B. The player should follow the terrain height but slow going up cliffs and then ...
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2answers
2k views

Render a polyline with rounded joints

I have a list of points (3D) and want to draw a line connecting all points with a specified width. The line should be rendered in OpenGL (using OSG) as triangles. The real challenge of this task is to ...
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1answer
105 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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1answer
229 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 ...
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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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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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1answer
78 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 ...
1
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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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1answer
293 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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2answers
124 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 ...
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1answer
559 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 ...
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1answer
68 views

Build a Cube/Prism from other varied Cubes/Prisms [closed]

I'm wondering, are there any algorithms or theories in existence (that aren't patented/proprietary/protected) that would take a series of 3d rectangular prisms (or cubes but a cube is a prism) and ...
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2answers
118 views

ricocheting off a wall

I have a capsule (sphere sweep) that I've computed the collision on a mesh with. I know the point of impact and normal of the face it collides with. My moving object - I'm using a capsule to ...
1
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2answers
2k views

Wrong faces culled in OpenGL when drawing a rectangular prism

I'm trying to learn opengl. I did some code for building a rectangular prism. I don't want to draw back faces so I used glCullFace(GL_BACK), glEnable(GL_CULL_FACE);. But I keep getting back faces also ...
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2answers
1k views

Segment-Cylinder intersection

What is the complete code (C#, pseudo, does not matter) for calculating the resulting segment (or its absence) for the intersection of asegment and a cylinder? The segment is defined by ...
1
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1answer
342 views

How do I determine if a tile is a slope based on the tile image?

In my game, every tile is a 32x32 texture. All the slopes are a 0 - 45 degree angle. I would like to determine, at the time I load the tile, if the is sloped by examining its texture/bitmap data. How ...
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2answers
482 views

Rotating coordinate system

Lets say that you want to rotate simple cube around fixed point in center. Is it possible to use such coordinate system, that you need to use only sine and cosine in order to rotate? I have done ...
1
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1answer
52 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
175 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
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
77 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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2answers
112 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. ...
1
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1answer
89 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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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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1answer
94 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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1answer
259 views

Batching and performances

I'm trying to understand batching and I'm not sure to understand how to do that, can I have more informations please? Here is what I found for the moment: Batching informations There is many types ...
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2answers
566 views

DirectX How to Gernerate Vertices for Diamond Shape and Render it?

How to generate vertices for 3D Diamond Shape in DirectX? EDIT: I am creating an application which receive DIAMETER, CROWN, GIRDLE and PAVILION as parameter and render a model of diamond according to ...
1
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1answer
170 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
423 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 = [ ...