TheGameCreators - CodeBase - Testing for point in a triangle

Category: 3D Maths

Version: 1.0

Information

Uploaded: 30th Aug 2003 12:34

Modified: 30th Aug 2003 12:37

Author: haggisman

Summary

This code shows a relatively simple way of finding out whither a point lies inside a triangle using some of the 3D math commands inside DBpro. It shows a simple case in 2D but can very easily be expanded to 3D.

Full Description

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

Rem Project: Intersection testing

Rem ***** Main Source File *****

`Normal setup code

Sync On : Sync Rate 0 : autocam off : randomize timer()

`Generate three triangle vertexs

X1=rnd(510)+1 : Y1=rnd(510)+1

X2=rnd(510)+1 : Y2=rnd(510)+1

X3=rnd(510)+1 : Y3=rnd(510)+1

`Variables required

Vect1=1

Vect2=2

Vect3=3

`Make vectors

rf=make vector2(Vect1)

rf=make vector2(Vect2)

rf=make vector2(Vect3)

cls

MX=mousex()

MY=mousey()

`draw the triangle

ink RGB(255,255,0), RGB(0,0,0)

line X1, Y1, X2, Y2

line X3, Y3, X2, Y2

line X1, Y1, X3, Y3

ink RGB(255,255,255), RGB(0,0,0)

`create 3 vectors from mouse coords to triangles vertices

set vector2 Vect1, MX-X1, MY-Y1

set vector2 Vect2, MX-X2, MY-Y2

set vector2 Vect3, MX-X3, MY-Y3

`normalize the vectors so their magnitude is now 1

normalize vector2 Vect1, Vect1 : normalize vector2 Vect2, Vect2 : normalize vector2 Vect3, Vect3

`calculate the angle between each vector and sum up

Angle_sum#=(acos(dot product vector2(Vect1, Vect2)))+(acos(dot product vector2(Vect2, Vect3)))+(acos(dot product vector2(Vect3, Vect1)))

`check if angle is 360 ish

If Angle_sum#>359.0 and Angle_sum#<361.0

`draw the lines to intersection point

line X1, Y1, MX, MY

line X3, Y3, MX, MY

line X2, Y2, MX, MY

Endif

text 0, 0, "ANGLE: " + str$(Angle_sum#)

sync

loop

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Author Name:	haggisman
CodeBase Entries:	2

CodeBase - Testing for point in a triangle