Re: A89: Re: 3D rotation of plots

To: assembly-89@lists.ticalc.org
Subject: Re: A89: Re: 3D rotation of plots
From: Nate Mueller <nlmueller@students.wisc.edu>
Date: Wed, 13 Jan 1999 16:55:10 -0500
Delivered-To: assembly-89-outgoing@towerguard.unix.edu.sollentuna.se
In-Reply-To: <004a01be3f46$739bbf00$4d1b7ed1@EDDIE>
Reply-To: assembly-89@lists.ticalc.org


>I just asked about this, as I am trying to write something 3D in M68k, and
I would also like to know
>how to plot a 3D point on the 89's 2D screen, if anyone can help.

I answered a question just like this about a month ago.  I'll try to
re-hash it now, but if I were you I'd look in the archive at ticalc.org.

Projecting a 3D point onto a 2D screen is simple.

			|
			|
			|
	*	 |	|
		 |	|
<---------#------------|----------+---->
		 |	|
		 |	|
			|
			|
			|

In this picture the * is point <x,y,z>.  the small vertical line is the
screen, the horizontal line is the z axes, and the large vertical line is
the y axes.  The observer is at <0,0,0>.  The first step is to translate
every point so that the origin appears to be at <0,0,#>.  Then you draw a
line from that point <x,y,z+#> back to the origin.  Where that line
intersects the plane of the screen is where you plot the point on the
calc's screen.  I did all the math in my previous post.

	--Nate

References:

A89: Re: 3D rotation of plots

From: "Miles Raymond" <m_rayman@bigfoot.com>

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