Questions tagged [geometry]

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

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Generation of a 3D loop the loop with minimal steering required

How would I generate a surface which resembles a loop-the-loop shape like this one described here? After triangulation of the surface, lets say I start at one end with some initial velocity which is ...
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50 views

How to know if two surface are in the same direction?

In my code I creat a Mesh that are composed by multiple tile. those tile can have edge that are shared, and I need to know if the normal of the tile that have shared edge have the same direction, ...
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Calculating approximations of contact between two meshes

I'm looking for ways to calculate the degree of contact between two objects in a scene. I was thinking that calculating the hausdorff distance would be a useful approximation if it is then normalized ...
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1answer
115 views

Convert 3D direction vectors to yaw/pitch/roll angles

I have the code below that takes a set of yaw, pitch, and roll rotation angles (in degrees), and populates forward, right, and up basis vectors to express this rotated orientation as a Cartesian ...
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Moving and rotating object with another object [duplicate]

Sorry i bad painter)) Need move and rotate 'OBJECT №2' with 'OBJECT №1' I have origin point(also rotation point) and angles of two object. (Also min and max coordinates of these objects) Vector ...
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1answer
51 views

How can I build an array of coordinates of a truncated icosahedron's faces?

I can easily get a list of coordinates of all the vertices—the Wikipedia page has formulae and this page has a list of them, but that doesn't tell me which ones are part of which face. What I'd like ...
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1answer
74 views

Move and rotate one object to another C++ [3D]

I have two object, need attach 'TWO OBJECT' to 'ONE OBJECT'. I have vectors 'angle' 'origin' of ONE and TWO objects. I tried do "TWOOBJECT.origin += ONE.origin - ONE.oldorigin", this just attach ...
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68 views

How to detect least distance to line segments calculation

I'm trying to calculate the distance of the player to a few lines that intersect two points, and return the smallest distance (i.e. tell me which of the lines the player is closest to/how far the ...
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1answer
83 views

Click on an isometric plane and obtain normal coordinates

I have photos distributed as cells. When I click, I get the corresponding row and column. console.log("Col:" + X + "Row:" + Y); When applying an isometric view conversion like this: ctx.translate(0, ...
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2answers
198 views

Most efficient way to get the closest point to a 3d rectangle

I have a 3D rectangle, with 4 points (x,y,z) And I have a player, who can be anywere (inside the rectangle, outside, not even in the plane, in the corner...). I would like to get the closest point in ...
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algorithm to change the center of the image

I need and algorithm in Java if possible to change the center of the image when scaling.What is happening to me is represented in the first image: when I scale the image the image scale according to ...
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43 views

Unity3D - Generate a position within a circular band around the player

Given a certain condition in my game I need to generate a position around the player. It needs to be at least 8 meters away from him and within 10 meters, in a circular matter, as in the dotted green ...
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Object's plane on image

I have a segmented image. So, for example, I know 2D coordinates of pixels for road on image. Now I want to know a plane of this road. How can I do this? P.S. I think it's popular problem, so I'm ...
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35 views

Calculating surface normal numerically

Say I have a 2D surface defined with the use of bitmap. I want to use this bitmap for collision detection (white color is where object can move freely, with black I mark the walls). How can I ...
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1answer
72 views

Get a Jump normal gravity based on Attractor Points, lines or Quad placed in the Level Design (in a Mario galaxy like gravity)

I have an algorithme to find. I have a player in a 3D space on a random planet. My goal is to have an oriented gravity toward my planet. And when I jump: Find the right normal direction. BUT I can't ...
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58 views

Getting the Closet Points between Polygons with the GJK Algorithm

I am trying to implement the GJK algorithm by following this lecture. For the most part, it is working, but sometimes 1 of the 2 closest points is incorrect. Here are two examples: EXAMPLE 1: The ...
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123 views

Find transformation to align two polygons at fixed points?

Problem I have a source image (arbitrary width and height c) shown here as a rectangle [X1,X2,X3,X4]. It contains two points C and D (both known coordinates within ...
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1answer
77 views

How to determine polygon based on point lists?

I have several lists of interconnected points. They are ordered so I can connect them together. Using these interconnected points I'd like to find the different points and intersection points that ...
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20 views

Is it possible to generate a 2D surface that approaches certain mesh, and then a specialised ray-tracing function for it?

As an example, suppose we are trying to ray-trace a sphere. There are two options. The first one is to build a mesh of triangles approximating the sphere and ray trace it. Unfortunately, the more ...
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1answer
36 views

Interpreting focal length in units of pixels

I am working on a renderer of sorts and I have some fundamental questions. Let's say I have a vector in a 3D virtual world space which is unitless, and I want to project it onto a 2D screen, so I need ...
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3answers
160 views

Get closest point on box to line

Eventually this problem will be 3D, so I would like a solution that works in 3D. My player is looking forwards. There is an axis-aligned box on the screen (FOV is guaranteed to be 90, so boxes behind ...
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3answers
106 views

How can you tell if you are a large player on a large map or a small player on a small map?

If everything is scaled by a constant factor, can you tell that the world is smaller or larger? I think you could look down at the ground and see that it's "closer". But how do you know what ...
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1answer
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Get the mesh Project Plane on Click and calculate its area

Here is the excerpt of my script which is calculating the surface area and face area of a mesh on OnMouseDown Event. ...
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1answer
950 views

How to calculate the surface area of a mesh

I am looking for a way to calculate surface area of a 3D mesh object and found this code from a Unity forum: ...
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1answer
77 views

How can I express Logarithmic and Arithmetic spirals as segmented cubic bezier curves?

I am creating cubic bezier curves using this code from another question I asked. I would like to know how I can express Logarithmic and Arithmetic spirals as segmented cubic bezier curves.
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71 views

How to inflate geometry?

I have a shape containing vertices and triangles I want to inflate that geometry using some radius to get something like that I should move each point along ...
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1answer
432 views

Why are spherical worlds so rare?

I remember back in the 90s when X-Com came out, being really impressed by the way its world map was an actual world: a map of Earth drawn on a spherical surface. That was pretty cool, because I had ...
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93 views

Confused by scaling, units, and more

Ok, so I've already waded through a bunch of questions around this, and it's just making me even more confused. Let's say I am trying to model a card table in a 2d game. Behind (beneath) the table ...
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1answer
37 views

Determine view-matrix with camera placed in a scene graph

My scene is organized with a simple scene graph where the child multiplies its transformation with the one of the parent. For normal objects, likes meshes, this works as expected, but I also want to ...
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1answer
84 views

Get triangles after subdivision

I was able to do subdivision on a triangle mesh with midpoints but then I get polygons with too many faces. How do I convert to triangles after? Similar to this picture:
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1answer
51 views

How to implement level-player collisions resolution?

I want to create simple collision response system (physical simulation is not required now). It is needed just that player can't go through walls. I consider some variants: - Just create a set of ...
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1answer
64 views

Define a circle from a point on its circumference and an angle

I'm working on a 2D, top-down driving game with some basic AI vehicles. The AI Vehicles move along a bidirected graph of positions. Each vehicle has a current position (from the graph) and a target ...
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Tetrahedron Circumsphere

Following this question, I want to create a sphere from a tetrahedron using this Wolfram support. But so far the resulted sphere is bigger than it should be and center seems to have an offset. ...
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2answers
456 views

How to draw a 3D capsule?

I want to draw a 3D capsule defined by a segment (two points start->end) and a radius: Image source: Orionist on Wikimedia Commons I already have a sphere leaning on this answer: https://...
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1answer
40 views

Aim/Scope Oscillation Algorithm

I have been struggling to find an algorithm to implement something that will make a direction oscillate within a cone constraint, in a helix-shaped fashion as in photo (it will always go back to the ...
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1answer
55 views

How can I find the reflection of a point in a perpendicular line?

From the image below I know the positions A and B. How can I find positions C and ...
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2answers
438 views

Getting the bounding box of a sphere

I have a sphere with values center,radius and I need to convert the sphere to a bounding box with values min,max. How do I ...
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2answers
266 views

Shrink a convex polygon

Shrinking a concave polygon is quite hard, to do well. But I expect shrinking a convex polygon would be easy. The naive approach of moving each vertex a certain distance to the centre gives me poor ...
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2answers
272 views

Find extreme points of a rotated ellipse function on a given axis

How to find the points where it is most extreme on the X and Y axis? For example lets say I have an equation that describes an ellipse that is rotated: ...
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1answer
617 views

Getting the winding order of a mesh

I'm doing some topological operations on my mesh and I need to know the winding order for my mesh. Since I will be importing models from different sources I will need to know whether the winding ...
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1answer
43 views

Display dynamic texture image on inside of sphere

I'm displaying a ring wherever the camera 'looks'. When the camera faces the ground (green) the ring image always looks correct, see image: However, my scene is within a sphere (purple)... and when ...
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2answers
348 views

How can I convert my list of vertices and indices to a list of triangles?

I have a full 3D collision mesh that is represented by a list of vertices and another list of indices. I need to convert the list of vertices and the list of indices into a set of triangles. First I ...
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1answer
244 views

Removing duplicate vertices on a mesh

I have a set of vertices and another set of indices. Sometimes I find that I have duplicate vertices in my mesh. I tried at first to check if two identical vertices were in the array of vertices but ...
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1answer
95 views

How to get a reflex edge on a non-convex mesh

I am trying to implement a convex decomposition and I need to find the convex vertex on a mesh. Is there a algorithm that I can use to find the convex vertex on a mesh.
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How to implement a pannini projection in opengl?

I have read about the pannini projection, which involves (I think) projecting a scene onto a cyclinder instead of a rectangle. How can I implement this projection in a vertex shader? Blinky is using ...
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1answer
50 views

How perform for obj follow mouse with angle?

how i can perform for sprite follow mouse if i change angle ? If i change angle the sprite no more follow mouse correctly. I absolutely need the obj follow mouse with pivot. https://jsfiddle.net/...
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2answers
151 views

Getting position of a coordinate on the surface of a sphere

So I want to create a object B close to another object A, but I'm trying to avoid that A covers B: I have thinking how to achieve that. Take a look of the following drawing: I have been thinking in ...
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1answer
94 views

Find ID from Spiral x, y positions. Hard programming formula

I have a formula, which gets coordinates from user_id (see below). I give User_id, and I get back coordinates. But now I need to get User_id from coordinates. For example: ...
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1answer
84 views

Draw triangles around screen

I am trying to draw triangles around the screen something like this: This is my script which can draw 6 triangles but I am not sure how to expand it to draw more like 8 or 10 triangles. Any help is ...
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Distance from capsule center to point on the surface

this question is engine agnostic, I will use the term "object" to refer to entities in my scene. The scenario is the following: I have 2 entities Entity O is a capsule Entity C is a point I want to ...