Problems with triangle generation

CoderHusk · December 9, 2020, 9:33pm

I am trying to generate triangles from wedges and 3 points in euclidean space (think like 3d) and I am using this module from @EgoMoose

github.com

EgoMoose/Articles/blob/master/3d triangles/3D triangles.md

# 3D Triangles

On occasion you may find it necessary to draw triangles given three points in 3D space. This article aims to go over one method that can be used to create those triangles using knowledge of trigonometry and coordinate frames.

## Table of contents

* [Triangle decomposition](#triangle-decomposition)
* [Manipulating the rotation matrix](#manipulating-the-rotation-matrix)
* [Optimization](#optimization)

## Triangle decomposition

The first thing we need to be aware of is that Roblox does not have a singular default shape that can be used to create any 3D triangle. However, a shape that Roblox does have is right-angle triangles, otherwise known as wedges. Thus, we can decompose any triangle into a maximum of two right-angle triangles and draw from there. We can easily draw this process by placing a perpendicular line on the longest edge and having it intersect with the opposite vertex.

![img1](imgs/img1.png)

Now that we understand the basics of our goal we have to ask ourselves how we can achieve this mathematically. We'll start this process off by finding some information about the triangle depending on what side is the longest.

![img2](imgs/img2.png)

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However when attempting to use the module I get an error saying that these dot products are basically nil

local abd, acd, bcd = ab:Dot(ab), ac:Dot(ac), bc:Dot(bc);

My main code is this

local triangleModule = require(script.GenerateTriangle)

triangleModule.draw3dTriangle(0, 1, 5, workspace)

Here is the place file Baseplate.rbxl (20.0 KB)

MrNicNac · December 9, 2020, 9:37pm

It expects Vector3s. Not numbers.

The error isn’t saying they’re nil. It’s saying you’re trying to call Dot() on a number.

CoderHusk · December 9, 2020, 9:40pm

How do I fix it then? I didn’t write the code I just got it from github

starmaq · December 9, 2020, 9:40pm

:Dot() is a method of Vector3, looking at the module’s code, ab, ac, and bc are the result of a series of subtractions between the first three inputted arguments. Meaning those three arguments should be vectors, not numbers, presumably representing the 3D position of each of the triangle’s vertices.

It’s better to read the article before blindly using the code, else use a documented module.

CoderHusk · December 9, 2020, 9:40pm

Could you link one with documentation?

starmaq · December 9, 2020, 9:42pm

I couldn’t find any, but you can look for yourself. If you end up not finding one, just go back to egomoose’s article, and try to understand what the a, b and c arguments need to be. Like I said, they’re probably the positions of vertices.

MrNicNac · December 9, 2020, 9:43pm

This is what you’re trying to do.

You gave the function a single number, which I imagine you thought was a 3D point. You clearly can’t draw a triangle with just that yellow dot above.

What you need to do is give it three points in 3D space like this.

local triangleModule = require(script.GenerateTriangle)

triangleModule.draw3dTriangle(Vector3.new(5,0,0), Vector3.new(0,5,0), Vector3.new(0,0,5), workspace)