
DIRECTORY G3dBasic, G3dNormalCoding, G3dVector, Random, Real, RealFns;

G3dNormalCodingImpl: CEDAR PROGRAM
IMPORTS G3dVector, Random, Real, RealFns
EXPORTS G3dNormalCoding

~ BEGIN
Triple:					TYPE ~ G3dBasic.Triple;
RandomStream:			TYPE ~ Random.RandomStream;
NtoGTable:				TYPE ~ ARRAY [0 .. 17] OF ARRAY [0 ..17] OF INT;
GtoNTable:				TYPE ~ ARRAY [0 .. 255] OF Triple;
ntogTable: NtoGTable м InitNtoGTable[];
gtonTable: GtoNTable м InitGtoNTable[];
rs: RandomStream м Random.Create[range: 500, seed: 1989];
EncodeNormal: PUBLIC PROC [dx, dy: REAL, dither: BOOLEAN м TRUE, userRS: RandomStream м NIL] RETURNS [pval: INT] ~ {
scale: REAL м 8.5;		-- 17/2.0
dz: REAL м 1.0 - ((dx * dx) + (dy * dy));
xentry, yentry: INT;
lrs: RandomStream м IF userRS = NIL THEN rs ELSE userRS;
IF dz < 0.0 
THEN RETURN[0]
ELSE {
IF dither THEN {
slip: REAL м 3.0/17.0;  -- use 3.0/17.0 for good results, 1.0/17.0 for debugging
scale: REAL м (2.0 * slip) / 499.0;
xfuzz: REAL м (scale * Random.NextInt[lrs]) - slip;
yfuzz: REAL м (scale * Random.NextInt[lrs]) - slip;
dx м dx + xfuzz;
dy м dy + yfuzz;
dz м (dx * dx) + (dy * dy);
IF dz > 1.0 THEN { dz м RealFns.SqRt[dz];  dx м dx  / dz;  dy м dy / dz; };
};
xentry м MIN[16, Real.Floor[(1.0 + dx) * scale]];
yentry м MIN[16, Real.Floor[(1.0 + dy) * scale]];
RETURN[ntogTable[yentry][xentry]];
};
};

DecodeNormal: PUBLIC PROC [pval: INT] RETURNS [n: Triple] ~ {
RETURN[gtonTable[pval]];
};

IsValidNormalIndex: PUBLIC PROC [index: INT] RETURNS [BOOLEAN] ~ {
RETURN[index >= 6 AND index < 255];
};

BuildNormalTables: PUBLIC PROC [] ~ {
ntogTable м InitNtoGTable[];
gtonTable м InitGtoNTable[];
rs м Random.Create[range: 500, seed: 1989];
};


InitNtoGTable: PROC [] RETURNS [ng: NtoGTable] ~ {

GridCheck: PROC [centerx, centery, size: REAL] RETURNS [BOOLEAN] ~ {
d: REAL м 1.0 - ((centerx * centerx) + (centery * centery));
IF d > 0.0 THEN RETURN [TRUE]
ELSE {
lx: REAL м centerx - size;
hx: REAL м centerx + size;
ly: REAL м centery - size;
hy: REAL м centery + size;

IF (lx*lx) + (ly*ly)		< 1.0 THEN RETURN [TRUE];
IF (lx*lx) + (hy*hy)	< 1.0 THEN RETURN [TRUE];
IF (hx*hx) + (hy*hy)	< 1.0 THEN RETURN [TRUE];
IF (hx*hx) + (ly*ly)	< 1.0 THEN RETURN [TRUE];
RETURN [FALSE];
};
};

width: INT м 17;
current: INT м 6;
iwidth: REAL м 1.0/width;
offset: REAL м iwidth - 1.0;
inc: REAL м 2.0 * iwidth;
FOR y: INT IN [0 .. width) DO
ny: REAL м offset + (y * inc);
FOR x: INT IN [0 .. width) DO
nx: REAL м offset + (x * inc);
IF GridCheck[nx, ny, iwidth] 
THEN { ng[y][x] м current; current м current+1; }
ELSE { ng[y][x] м -1; };
ENDLOOP;
ENDLOOP;
};

InitGtoNTable: PROC [] RETURNS [gn: GtoNTable] ~ {
hits: INT;
offset: REAL м -16.0/17.0;
inc: REAL м 2.0/17.0;
FOR a: INT IN [0 .. 255] DO gn[a] м [-1.0, -1.0, -1.0]; ENDLOOP;
FOR y: INT IN [0 .. 16] DO
FOR x: INT IN [0 .. 16] DO
entry: INT м ntogTable[y][x];
IF entry > 0 THEN {
ulx: REAL м (x * inc) - 1.0;
uly: REAL м (y * inc) - 1.0;
wid: REAL м inc / 5.0;
norm: Triple м [0.0, 0.0, 0.0];
hits м 0;
FOR i: INT IN [0 .. 5] DO
fy: REAL м uly + wid*i;
FOR j: INT IN [0 .. 5] DO
fx: REAL м ulx + wid*j;
fz: REAL м (fx*fx)+(fy*fy);
IF fz <= 1.0 THEN {
fz м RealFns.SqRt[1.0 - fz];
norm м G3dVector.Add[norm, [fx, fy, -fz]];
hits м hits + 1;
};
ENDLOOP;
ENDLOOP;
gn[entry] м G3dVector.Unit[norm];
};
ENDLOOP;
ENDLOOP;

};

END.

  └  
G3dNormalCodingImpl.mesa
Copyright ╙ 1985, 1992 by Xerox Corporation.  All rights reserved.
Glassner, April 14, 1989 1:35:37 pm PDT
Bloomenthal, July 15, 1992 10:43 pm PDT
Types
Custom Types
Globals
-- NOTE that the order of these calls is important
Encode a G3dRender Context3d
EncodeAllNormals: PUBLIC PROC [context3d: Context3d] ~ {
Action: PROC ~ {
width: NAT _ Real.Fix[context3d.viewPort.w];
height: NAT _ Real.Fix[context3d.viewPort.h];
scanSeg: PixelBuffer _ ImagerPixel.NewPixels[context3d.pixels.samplesPerPixel, width];
refV: REF NAT _ NARROW[Atom.GetPropFromList[context3d.displayProps, $NormalBuffer]];
v: NAT;
IF refV # NIL 
THEN {  v _ refV^;  } 
ELSE G3dRender.Error[$Fatal, "Normals not available"];
FOR y: NAT IN [0..height) DO
ImagerPixel.GetPixels[										-- get scanline of pixels
self: context3d.pixels, pixels: scanSeg, initIndex: [f: 0, s: y], count: width ];
FOR x: NAT IN [0..width) DO
IF scanSeg[v+2][x] > 0 
THEN scanSeg[0][x] _ EncodeNormal[ 
LOOPHOLE[scanSeg[v  ][x], INTEGER]/32768.0, 
-LOOPHOLE[scanSeg[v+1][x], INTEGER]/32768.0 
]
ELSE scanSeg[0][x] _ 0;
ENDLOOP;
ImagerPixel.PutPixels[											-- return modified pixels
self: context3d.pixels, pixels: scanSeg, initIndex: [f: 0, s: y], count: width
];
ENDLOOP;
IF context3d.viewer # NIL THEN context3d.class.drawInViewer[ 
context3d, 
NEW[G3dRender.ImagerProcRec _ [G3dColorDisplaySupport.StuffBuf, NIL]] 
];
};
CedarProcess.DoWithPriority[background, Action];				-- be nice to other processess
};

Normal Encoding/Decoding Procedures
Normal Table Creation
The Normal Table:
We reserve 9 entries for special use:
0: Foreground color (usually black)
255: Background color (usually white)
1: Light Source Swatch
2: Material Swatch
3-5: Reserved
Thus there are 249 entries left, in the range [6 .. 254], all of which are used.

-- NOTE that the order of these calls is important
the following calls are in no special order
-- NOTE!  You must call InitNtoGTable before calling InitGtoNTable

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