3d Calculations

[Basjuh]

Does anybody know the exact calculations for displaying a 3d object on the screen... i have already the sqrt(x,y,z) but that only gives the distance from the 0,0,0 point and i still need the angle of that line...

[tr1p1ea]

Do you mean points only?

Generally:

X = (256 * (X / (Z + zCenter)) + xCenter)
Y = (256 * (Y / (Z + zCenter)) + yCenter)

This will give you the correct position as well as perspective ... but u might have to play around with the zCenter and the 256 a little.

Still it wont be fast in basic.

[Basjuh]

yes points only.

what value have zCenter,yCenter and xCenter? thats the 0,0,0 point right?

i know it wont be fast but i just use it for testing, making it faster and maybe using it for somthing...

[Basjuh]

and why 256 you'll get really big values that way....

[tr1p1ea]

xCenter, and yCenter are used because the native 0,0 part of the screen is the top left corner. Adding these two will make 0,0 in the middle of the screen.

xCenter = ScreenWidth / 2 ... so its just (96 / 2)
yCenter = ScreenHeight / 2 ... so its just (64 / 2)
zCenter = How far away from the screen you want the center point to be ... play with this value, 128 or 256 work pretty good.

As far as the 256 at the start goes ... well 128 might be a better alternative. Lets plug in some values.

say u have x = 10, y = 10, z = 10. Now:

X = (128 * (X / (Z + zCenter)) + xCenter)
Y = (128 * (Y / (Z + zCenter)) + yCenter)

therefore:

X = (128 * (10 / (10 + 256)) + 4
Y = (128 * (10 /( 10 + 256)) + 32)

You MUST convert to integer .. with 'int()'.

X_Pos = 53
Y_Pos = 37

So you would draw your point at (53,37). That seems fine to me (as the 0,0 is really at the center of the screen ... so the points 'really' convert to (5,5)).

Just play around with the values to see what looks right.

[Basjuh]

Great you're the man it works perfectly....

[tr1p1ea]

Hey no problem .... do you want to know about rotations and stuff?

[Basjuh]

if you can tell me ok, i know its some calculation with sinus and cosinus, but i dont know it anymore

[tr1p1ea]

Ok Rotations :)

Around the X-Axis:

X = X
Y = Y * Cos(Pitch) - Z * Sin(Pitch)
Z = Y * Sin(Pitch) + Z * Cos(Pitch)

Around the Y-Axis:

X = Z * Sin(Yaw) + xT * Cos(Yaw)
Y = Y
Z = Z * Cos(Yaw) - xT * Sin(Yaw)

And About the Z-Axis:

X = Y * Sin(Roll) + X * Cos(Roll)
Y = Y * Cos(Roll) - X * Sin(Roll)
Z = Z

Ok Pitch, Yaw & Roll are all angles of rotation. These work well with really small values (like 0.1). Dont forget to convert with int() before displaying .

[Arcane Wizard]

[sgm]

[tr1p1ea]

Well applying a rotation matrix would be a good idea, however i wanted to show what exactly is going on. Plus im hardly an expert in the subject .

[Jedd]

Kinda off topic....are there any BASIC game programs that have successfully simulated a decent 3-D environment? I downloaded resident evil and it was horrible (graphics, movement, shooting etc).