Solid5 6/8

 BBS: Inland Empire Archive
Date: 03-21-93 (03:44)             Number: 356
From: RICH GELDREICH               Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: Solid5 6/8                     Conf: (2) Quik_Bas

'Page 6 of SOLID5.BAS begins here.
    ShadowXHigh(s) = XHigh: ShadowYHigh(s) = YHigh
    IF XHigh < 0 OR XLow > 319 OR YLow > 199 OR YHigh < 0 THEN EXIT SUB
    IF YHigh > 199 THEN YHigh = 199
    IF YLow < 0 THEN YLow = 0

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

    'Enter the lines into the edge list
    FOR a = 0 TO MaxLines
        P1 = lines(a).P1
        P2 = lines(a).P2
        DrawLine (Points(P1).XShadow), (Points(P1).YShadow), (Points(P2_
).XShadow), (Points(P2).YShadow), EdgeList()
        'LINE ((Points(P1).XShadow), (Points(P1).YShadow))-((Points(P2)_
.XShadow), (Points(P2).YShadow)), 0
    NEXT

    'Fill the polygon
    EdgeFill EdgeList(), YLow, YHigh, 3

END SUB

SUB EdgeFill (EdgeList() AS EdgeType, YLow, YHigh, C)
    FOR a = YLow TO YHigh
        LINE (EdgeList(a).Low, a)-(EdgeList(a).High, a), C
    NEXT
END SUB

'This routine initializes the data required by the fast Lambert shading
'algorithm. It calculates the point which is both perpendicular
'and a constant distance from each polygon and stores it. This point
'is then rotated with the rest of the points. When it comes time for
'shading, the normal to the polygon is looked up in a simple lookup
'table for maximum speed.
SUB FindNormals
    FOR a = 0 TO MaxPolys
        P1 = Polys(a).P1: P2 = Polys(a).P2: P3 = Polys(a).P3

        'find the vectors of 2 lines inside the polygon
        ax! = Points(P2).XObject - Points(P1).XObject
        ay! = Points(P2).YObject - Points(P1).YObject
        az! = Points(P2).ZObject - Points(P1).ZObject

        bx! = Points(P3).XObject - Points(P2).XObject
        by! = Points(P3).YObject - Points(P2).YObject
        bz! = Points(P3).ZObject - Points(P2).ZObject

        'find the cross product of the 2 vectors
        nx! = ay! * bz! - az! * by!
        ny! = az! * bx! - ax! * bz!
        nz! = ax! * by! - ay! * bx!

        'normalize the vector so it ranges from -1 to 1
        M! = SQR(nx! * nx! + ny! * ny! + nz! * nz!)
        IF M! <> 0 THEN nx! = nx! / M!: ny! = ny! / M!: nz! = nz! / M!
        'store the vector for later rotation(notice that it is scaled
        'up by 128 so it can be stored as an integer variable)
        Polys(a).WorldXN = nx! * 128 + Points(P1).XObject
        Polys(a).WorldYN = ny! * 128 + Points(P1).YObject
        Polys(a).WorldZN = nz! * 128 + Points(P1).ZObject
    NEXT
END SUB

'Draws a polygon to the screen. Simply finds the start and stop X
'coordinates for each scan line within the polygon and uses the
'LINE command for filling.
SUB PolyFill (x1, y1, x2, y2, x3, y3, C) 'for QB 4.5 guys

    'find lowest and high X & Y coordinates
    IF y1 < y2 THEN YLow = y1 ELSE YLow = y2
    IF y3 < YLow THEN YLow = y3
    IF y1 > y2 THEN YHigh = y1 ELSE YHigh = y2
    IF y3 > YHigh THEN YHigh = y3

    IF x1 < x2 THEN XLow = x1 ELSE XLow = x2
    IF x3 < XLow THEN XLow = x3
    IF x1 > x2 THEN XHigh = x1 ELSE XHigh = x2
    IF x3 > XHigh THEN XHigh = x3

    IF YLow < 0 THEN YLow = 0

    IF YHigh > 199 THEN YHigh = 199


    IF XLow < XLow(s) THEN XLow(s) = XLow
    IF XHigh > XHigh(s) THEN XHigh(s) = XHigh

    IF YLow < YLow(s) THEN YLow(s) = YLow
    IF YHigh > YHigh(s) THEN YHigh(s) = YHigh

'Continued on page 7

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