Vertice Rotation Calculation.

[JS Lemming]

Does anyone happen to know the formulas for calculating the 4 vertices coordinates after a given rotation? If not, I guess I can try to make my own real fast.

[Falco Girgis]

Tvspelsfreak has mastered rotations. I just barely started Geometry, so I'm not so hot on my sine, cosine and tangent.

[JS Lemming]

The best scenerio would be a function like.

RotateVert(CenterOfRotation,Vert,angle)

I'll figure it out later.

[Tvspelsfreak]

Basically something like this:

Code: Select all

V1  __________________  V2
   |                  |
   |                  |
   |                  |
   |                  |
   |      Origin      |
   |                  |
   |                  |
   |                  |
   |                  |
V3  ------------------  V4

That's supposed to be a (width)x(height) sprite positioned at the origin.
To calculate the 4 vertices positions at any angle of rotation you do:

Code: Select all

tempx = vertex.x - origin.x;
tempy = vertex.y - origin.y;
x = origin.x+(tempx*cos(angle)-tempy*sin(angle));
y = origin.y+(tempx*sin(angle)+tempy*cos(angle));

Where (x,y) is the new position after rotating.

So as an example, here's the code to rotate the sprite above:

Code: Select all

tempx = origin.x - width/2 - origin.x;
tempy = origin.y - height/2 - origin.y;
v1.x = origin.x+(tempx*cos(angle)-tempy*sin(angle));
v1.y = origin.y+(tempx*sin(angle)+tempy*cos(angle));
tempx = origin.x + width/2 - origin.x;
tempy = origin.y - height/2 - origin.y;
v2.x = origin.x+(tempx*cos(angle)-tempy*sin(angle));
v2.y = origin.y+(tempx*sin(angle)+tempy*cos(angle));
tempx = origin.x - width/2 - origin.x;
tempy = origin.y + height/2 - origin.y;
v3.x = origin.x+(tempx*cos(angle)-tempy*sin(angle));
v3.y = origin.y+(tempx*sin(angle)+tempy*cos(angle));
tempx = origin.x + width/2 - origin.x;
tempy = origin.y + height/2 - origin.y;
v4.x = origin.x+(tempx*cos(angle)-tempy*sin(angle));
v4.y = origin.y+(tempx*sin(angle)+tempy*cos(angle));

All angles have to be in radians, to convert from degrees to radians do:

Code: Select all

rad_angle = deg_angle*(PI/180);

[JS Lemming]

GuuHAHHHAA YES! Woot! Now I don't have to think of that myself. Thanks Tvspelsfreak!

[Falco Girgis]

That's what made the most awesome LEVEL 1 thing in Melchior, which is Tvspelsfreak's first released homebrew for the DC.

I think you at least owe it a download and play. It's a great game. Tvspelsfreak is t3h 1337.

[Tvspelsfreak]

If anything, download the binary files and transfer through the coders cable.
It's not really worth wasting a disc.

[Falco Girgis]

I used a well-worth it disc.

[JS Lemming]

You know, I never even thought to think to see if Tvspelsfreak had made a homebrew.... I'm not sure why. Anyway, where can I obtain this and about how big was it (in megab)? Do you have your own site or something? Sounds koo.

[Falco Girgis]

http://dcemulation.com should have the binary files as far as I know.

Tvspelsfreak sent me the the super secret 1337 .ELF file because I'm so cool.

I mean, you could just send the .bin to your DC via coder's cable, but it won't be as fast as the .ELF.

[Falco Girgis]

Sorry to move this, but WTF is it doing in DC discussion? Shame on you. . .

[JS Lemming]

err... well, it was for the DC.... and we don't have a math forum. sorry, I really didn't notice.

[Falco Girgis]

I don't know, there really is a hazy line between DC Dev and Programming discussion.

I like to classify programming things that are hardwares specific as "DC Dev" material, and things that are general programming as "Programming Discussion"

BTW, I rotated my first sprite fool! A rotating Nullset... w00t!