Solid5 7/8

 BBS: Inland Empire Archive
Date: 03-21-93 (03:44)             Number: 357
From: RICH GELDREICH               Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: Solid5 7/8                     Conf: (2) Quik_Bas

'Page 7 of SOLID5.BAS begins here.
    'check for polygons which cannot be visible
    IF YHigh < 0 OR YLow > 199 OR XLow > 319 OR XHigh < 0 THEN EXIT SUB

    'initialize the edge list
    FOR a = YLow TO YHigh
        EdgeList(a).Low = 32767
        EdgeList(a).High = -32768
    NEXT

    'Remember the lowest & highest X and Y coordinates drawn to the
    'screen for later erasing

    'Find the start and stop X coodinates for each scan line
    DrawLine (x1), (y1), (x2), (y2), EdgeList()
    DrawLine (x2), (y2), (x3), (y3), EdgeList()
    DrawLine (x3), (y3), (x1), (y1), EdgeList()
    EdgeFill EdgeList(), YLow, YHigh, C

END SUB

'Rotates the points of the object and the object's normals.
'Avoids floating point math for speed.
SUB RotatePoints

    'lookup the sine and cosine of each angle...
    s1& = SineTable(R1): c1& = SineTable(R1 + 90)
    s2& = SineTable(R2): c2& = SineTable(R2 + 90)
    s3& = SineTable(R3): c3& = SineTable(R3 + 90)

    'rotate the points of the object
    FOR a = 0 TO MaxPoints
        xo = Points(a).XObject
        yo = Points(a).YObject
        zo = Points(a).ZObject
        GOSUB Rotate3D

        Points(a).XView = 160 + (x2 * 400&) \ z3
        Points(a).YView = 100 + (y3 * 300&) \ z3
        'IF y3 > 300 THEN STOP

        Points(a).XWorld = x2
        Points(a).YWorld = y3
        Points(a).ZWorld = z3
    NEXT
    'rotate the normals of each polygon...
    FOR a = 0 TO MaxPolys
        xo = Polys(a).WorldXN
        yo = Polys(a).WorldYN
        zo = Polys(a).WorldZN
        GOSUB Rotate3D
        P1 = Polys(a).P1
        'unorigin the point
        x2 = x2 - Points(P1).XWorld
        y3 = y3 - Points(P1).YWorld
        z3 = z3 - Points(P1).ZWorld
        'check the bounds just in case of a round off error
        IF x2 < -128 THEN x2 = -128 ELSE IF x2 > 128 THEN x2 = 128
        IF y3 < -128 THEN y3 = -128 ELSE IF y3 > 128 THEN y3 = 128
        IF z3 < -128 THEN z3 = -128 ELSE IF z3 > 128 THEN z3 = 128
        'store the normal back; it's now ready for the shading
        'calculations (which are simplistic now)
        Polys(a).NormalX = x2 + 128
        Polys(a).NormalY = y3 + 128
        Polys(a).NormalZ = z3 + 128
    NEXT
    EXIT SUB

Rotate3D:
    x1 = (xo * c1& - zo * s1&) \ 1024 'yaw
    z1 = (xo * s1& + zo * c1&) \ 1024

    z3 = (z1 * c3& - yo * s3&) \ 1024 + oz 'pitch
    y2 = (z1 * s3& + yo * c3&) \ 1024

    x2 = (x1 * c2& + y2 * s2&) \ 1024 + ox 'roll
    y3 = (y2 * c2& - x1 * s2&) \ 1024 + oy

RETURN
END SUB

'Shades the polygons using Lambert shading. Notice the total lack of
'floating point math- only 1 divide is required for each polygon shaded.
'(This divide can be eliminated, but the shading won't be as accurate.)
SUB ShadePolygons
    FOR a = 0 TO MaxPolys
        IF Polys(a).Culled = False THEN
         'lookup the polygon's normal for shading
         '(128*128)\15 = 1092
         Intensity = (lx(Polys(a).NormalX) + ly(Polys(a).NormalY) + _
lz(Polys(a).NormalZ)) \ 1092
         IF Intensity < 0 THEN Intensity = 0
         Intensity = Intensity + 5
         IF Intensity > 15 THEN Intensity = 15
'Continued on page 8

--- MsgToss 2.0b
 * Origin: Computer Co-Op - Voorhees, NJ | Ted Hare (1:266/29)