Re: A86: polygons
[Prev][Next][Index][Thread]
Re: A86: polygons
The char theta represents an angle. thetaX is how many degrees to rotate
around the X axis. You can rotate different amounts around all 3 axis' to
get any POV.
At 10:00 AM 7/20/98 -0700, you wrote:
>
>Yeah I get most of it. But, what are "thetaX","thetaY".
>I know what the character looks like but what effect does
>it have on x and y?
>
>Tnx
>
>> To do 3D rotations you can use matrix multiplication. I frequently get
>> this backwards, so be careful:-).
>>
>> Rotate about the x-axis:
>> [[1, 0, 0]
>> [0, cos(thetaX),-sin(thetaX)]
>> [0, sin(thetaX), cos(thetaX)]]
>>
>> Rotate about the y-axis:
>> [[ cos(thetaY), 0, sin(thetaY)]
>> [ 0, 1, 0]
>> [-sin(thetaY), 0, cos(thetaY)]]
>>
>> Rotate about the z-axis:
>> [[cos(thetaZ),-sin(thetaZ), 0]
>> [sin(thetaZ), cos(thetaZ), 0]
>> [0, 0, 1]]
>>
>> the rotation matrix is multiplied by the (X,Y,Z) coordinates in the form:
>>
>> [[cos(thetaZ),-sin(thetaZ), 0] [[X] [[Xcos(thetaZ)-Ysin(thetaZ)]
>> [sin(thetaZ), cos(thetaZ), 0] * [Y] = [Xsin(thetaZ)+Ycos(thetaZ)]
>> [0, 0, 1]] [Z]] [Z]]:
>>
>> x = (Xcos(thetaZ)-Ysin(thetaZ))*25/(25-Z)
>> y = (Xsin(thetaZ)+Ycos(thetaZ))*25/(25-Z)
>
>--
>Tercero -- Email: mailto:tercero@busprod.com
>
>"The stone the builders rejected has become the capstone;"
> --Psalms 118:22
>"Everyone who falls on that stone will be broken to pieces,
>but he on whom it falls will be crushed."
> --Luke 20:18
>
--
David Phillips
mailto:electrum@tfs.net
ICQ: 13811951
AOL/AIM: electrum32
Follow-Ups:
References: