Developer CD Series 2000 November: Tool Chest/Dev.CD Nov 00 TC Disk 1.toast/Sample Code/Contributed/SpriteWorld/SpriteWorld Files/Utils/Brian's Extensions/SWLightingSquares.c

Text File | 2000-10-06 | 28.2 KB | 799 lines | [TEXT/CWIE]

/*  -----------------------------------------------------------------------------------
    -----------------------------------------------------------------------------------
    SWLightingSquares.c

    by Brian Roddy

    5/20/97


    ** N.B. These functions are still experimental.  They work fine, but the public API
       needs work to achieve better effects and uses.


    These routines are for an alternative style of getting lighting effects.  It's
    main function is a Screen Blitting procedures that takes the offscreen work area
    and colors it as it copies it on screen.  Thus the parts copied on screen can
    be made darker or lighter or a little reddish, etc.

    To support a feeling of lights, we divide the screen into a map of tiny squares
    and associate a color and a level with each square.  As we blit onto the screen,
    we use this map to color the image.  The result is that the screen image looks
    nicely colorized.  Imagine each square having a colored gel placed over top of
    it.

    The smaller the squares in our map, the finer the grain of lighting but the greater
    the overhead.  More space and speed are required.  We also provide routines for setting
    and managing this lighting map, including setting light levels and combining
    lights (so blue lights and yellow lights will become greenish lights as they overlap).

    These functions make use of the translucency table functions found in
    "SWTranslucentBlitters.c" and therefore that file needs to be present for this to
    work.

    Use SWInitializeLightingSquares(spriteWorldPtr, 8); to initialize the use of squares.
    8 in this case is the size of the squares in pixels.

    Use:
        SWSetLightingSquare(spriteWorldPtr, col, row,
                             color, opacity,
                             relativeP, makeDirtyP);
    to set a cell's value.  Opacity is the translucency levels (as in the translucent blitters).
    relativeP is a boolean specifying whether to set the color and level directly or to blend
    it together with what is already in the cell.   makeDirtyP forces sprite world to redraw
    that cell on the screen during the next draw loop.

    Use:
        SWLightUpArea (spriteWorldPtr, col, row,
                        color,  level
                        bigLightP);
    to light up an area around a cell.  This is good for spotlights.  bigLightP makes the light
    really big.  Note that this just calls     SWSetLightingSquare repeatedly.

    SWDarkenLightingSquares (spriteWorldPtr); will blend black into every square in the
    grid to darken everything.  This is a good example of how to achieve a lighting effect
    with these squares.

    Use SWExitLightingSquares (); to free up the tables when quitting.

    You may use these routines in a scrolling game, provided that you scroll in
    multiples of the lighting grid.

    The Lit Breakout Demo is an example of how to use these functions in an app.


    -------------------------------------------------------------------------------------
    Implementation Notes:

    The engine for all of this is the code for blitting Tinted Rects in 8 bit or in 16 bit
    mode.  There are straight C versions as well as versions that use optimize PowerPC
    assembly.

    This source code is available for free use.
    -----------------------------------------------------------------------------------
    ----------------------------------------------------------------------------------- */


///--------------------------------------------------------------------------------------
// Includes
///--------------------------------------------------------------------------------------

#include <SWTranslucentBlitters.h>
#include <SWLightingSquares.h>
#include <SWGameUtils.h>

unsigned long *gLitSquareColorTable;
unsigned long *gLitSquareLevelTable;
int gLightingSquareRows, gLightingSquareColumns;
int SWLitSquareSize    = 8;

unsigned long gBlackColor;

#pragma mark ----------- Public API -------------
SW_FUNC OSErr     SWInitializeLightingSquares (SpriteWorldPtr spriteWorldP,
                                            int squareSize) {
    long                arraySize;
    OSErr                err = noErr;

    SWLitSquareSize = squareSize;
    gLightingSquareColumns = ((spriteWorldP->windRect.right - spriteWorldP->windRect.left) / SWLitSquareSize) + 1;
    gLightingSquareRows = ((spriteWorldP->windRect.bottom - spriteWorldP->windRect.top) / SWLitSquareSize) + 1;

    SWExitLightingSquares ();

    if (err == noErr) {
        if (spriteWorldP->pixelDepth == 8) {
            SWSetSpriteWorldScreenDrawProc(spriteWorldP, BlitPixie8BitLitRectDrawProc);
            CreateCLUTTable();
            gBlackColor = ColorToIndex(0,0,0);
        } else if (spriteWorldP->pixelDepth == 16) {
            SWSetSpriteWorldScreenDrawProc(spriteWorldP, BlitPixie16BitLitRectDrawProc);
            gBlackColor = 0x0000;

        }
        else
            err = kWrongDepthErr;
    }

    if (err == noErr) {
        arraySize = gLightingSquareColumns * gLightingSquareRows * sizeof(unsigned long);
        gLitSquareColorTable = (unsigned long *)NewPtr(arraySize);
        err = MemError();
    }

    if (err == noErr) {
        arraySize = gLightingSquareColumns * gLightingSquareRows * sizeof(unsigned long);
        gLitSquareLevelTable = (unsigned long *)NewPtr(arraySize);
        err = MemError();
    }

    return err;
}

SW_FUNC void     SWExitLightingSquares ()
{
    // Only do this if we've created a table.
    if (gLitSquareColorTable != NULL) DisposePtr((Ptr)gLitSquareColorTable);
    if (gLitSquareLevelTable != NULL) DisposePtr((Ptr)gLitSquareLevelTable);
}



///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------
/// Table Management Functions
///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------

SW_FUNC void SWSetLightingSquare(SpriteWorldPtr swp, int col, int row,
                         unsigned long color, unsigned long level,
                         Boolean relative, Boolean makeDirty) {
    long index, curColor, curLevel, newColor, newLevel;
    Rect changedRect;

    // Bounds Checking
    if (! ((row < 0) ||
           (col < 0) ||
           (row >= gLightingSquareRows) ||
           (col >= gLightingSquareColumns))) {

        int maxLevel;
        if (swp->pixelDepth == 8)
            maxLevel = gNumberOf8BitTranslucencyLevels;
        else
            maxLevel = 32;
        if (level < 0) level = 0;
        if (level >= maxLevel) level = (maxLevel - 1);

        // Compute the data structure
        index = ((row * gLightingSquareColumns) + col);
        curColor = gLitSquareColorTable[index];
        curLevel = gLitSquareLevelTable[index];

        if (relative) {
            if (swp->pixelDepth == 8) {
                newColor = Blend8BitPixels(level, curColor, color);
            } else {
                newColor = Blend16BitPixels(level, curColor, color);
            }

            if (newColor == curColor)
                newColor = color;

            newLevel = (curLevel + level) / 2;
            if (newLevel == curLevel)
                newLevel = level;

        } else {
            newColor = color;
            newLevel = level;
        }

        // And if the value is different
        if ((curColor != newColor) ||
            (curLevel != newLevel)) {

            // Update the data structure
            gLitSquareColorTable[index] = newColor;
            gLitSquareLevelTable[index] = newLevel;

            if (makeDirty) {
                // And tell spriteworld that the square is dirty
                changedRect.top = row * SWLitSquareSize;
                changedRect.bottom = ((row + 1) * SWLitSquareSize);
                changedRect.left = col * SWLitSquareSize;
                changedRect.right = ((col + 1) * SWLitSquareSize);
                SWFlagRectAsChanged(swp, &changedRect);
            }
        }
    }
}

///--------------------------------------------------------------------------------------
///---- SWDarkenLightingSquares.
///
/// A utility function to do light fading over time.

SW_FUNC void SWDarkenLightingSquares (SpriteWorldPtr swp)
{
    int row, col, index = 0;
    int maxLevel;

    if (swp->pixelDepth == 8)
        maxLevel = gNumberOf8BitTranslucencyLevels - 1;
    else
        maxLevel = 30;

    for (row = 0; row < gLightingSquareRows; row++)
        for (col = 0; col < gLightingSquareColumns; col++) {
            if ((gLitSquareColorTable[index] != gBlackColor) ||
                (gLitSquareLevelTable[index] != maxLevel)) {
                int index = ((row * gLightingSquareColumns) + col);
                int curLevel = gLitSquareLevelTable[index];

                SWSetLightingSquare(swp, col, row, gBlackColor, maxLevel, (curLevel != maxLevel), true);
            }
            index++;
        }
}


///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------

SW_FUNC void SWLightUpArea (
    SpriteWorldPtr swp,
    int col,
    int row,
    unsigned long lightColor,
    int lightLevel,
    Boolean BigLight) {

    // Light up the tiles around the sprite.  Light up the center sprite and
    // adjacent ones really bright, Light up the four diagonally adjacent ones
    // fairly bright.

    // Calculate the light levels
    int lightLevelBorder = lightLevel;
    int lightLevelMiddle = lightLevelBorder; // + RandomNumber(2);

    Boolean blendIt = true;

    // and light them up
    SWSetLightingSquare(swp, col - 1, row - 1, lightColor, lightLevelBorder, blendIt, true);
    SWSetLightingSquare(swp, col    , row - 1, lightColor, lightLevelMiddle, blendIt, true);
    SWSetLightingSquare(swp, col + 1, row - 1, lightColor, lightLevelBorder, blendIt, true);
    SWSetLightingSquare(swp, col - 1, row    , lightColor, lightLevelMiddle, blendIt, true);
    SWSetLightingSquare(swp, col    , row    , lightColor, lightLevelMiddle, blendIt, true);
    SWSetLightingSquare(swp, col + 1, row    , lightColor, lightLevelMiddle, blendIt, true);
    SWSetLightingSquare(swp, col - 1, row + 1, lightColor, lightLevelBorder, blendIt, true);
    SWSetLightingSquare(swp, col    , row + 1, lightColor, lightLevelMiddle, blendIt, true);
    SWSetLightingSquare(swp, col + 1, row + 1, lightColor, lightLevelBorder, blendIt, true);

    if (BigLight)
    {   /// If BigLight is true then we make a really big light that
        /// lights up a 5x5 area of tiles rather than 3x3
        int lightLevelEdgeCorner = lightLevelBorder + 2;
        int lightLevelEdgeNearCorner = lightLevelBorder + 1;
        int lightLevelEdge = lightLevelBorder + 1;

        SWSetLightingSquare(swp, col - 2, row - 2, lightColor, lightLevelEdgeCorner, blendIt, true);
        SWSetLightingSquare(swp, col + 2, row - 2, lightColor, lightLevelEdgeCorner, blendIt, true);
        SWSetLightingSquare(swp, col - 2, row + 2, lightColor, lightLevelEdgeCorner, blendIt, true);
        SWSetLightingSquare(swp, col + 2, row + 2, lightColor, lightLevelEdgeCorner, blendIt, true);
        SWSetLightingSquare(swp, col - 1, row - 2, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col    , row - 2, lightColor, lightLevelEdge, blendIt, true);
        SWSetLightingSquare(swp, col + 1, row - 2, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col - 1, row + 2, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col    , row + 2, lightColor, lightLevelEdge, blendIt, true);
        SWSetLightingSquare(swp, col + 1, row + 2, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col - 2, row - 1, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col - 2, row    , lightColor, lightLevelEdge, blendIt, true);
        SWSetLightingSquare(swp, col - 2, row + 1, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col + 2, row - 1, lightColor, lightLevelEdgeNearCorner, blendIt, true);
        SWSetLightingSquare(swp, col + 2, row    , lightColor, lightLevelEdge, blendIt, true);
        SWSetLightingSquare(swp, col + 2, row + 1, lightColor, lightLevelEdgeNearCorner, blendIt, true);
    }

}


///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------
/// The Blitting Functions
///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------


#pragma mark ----------- 8 Bit Screen Draw Function -------------
///--------------------------------------------------------------------------------------
//        BlitPixie8BitLitRectDrawProc
///--------------------------------------------------------------------------------------

SW_FUNC void BlitPixie8BitLitRectDrawProc(
    FramePtr srcFrameP,
    FramePtr dstFrameP,
    Rect* srcRect,
    Rect* dstRect
    )
{
    Rect                     srcBlitRect = *srcRect;
    Rect                     dstBlitRect = *dstRect;
    unsigned long             numBytesPerRow;
    register unsigned char     *tableAtLevelAndIndex;
    int                     startRow, endRow, startCol, endCol, startSrcRow, startSrcCol;
    int                     row, col, index, srcRow, srcCol;
    Rect                     curSrcBlitRect, curDstBlitRect;

    SW_ASSERT(srcFrameP->isFrameLocked && dstFrameP->isFrameLocked);
    SW_ASSERT((*srcFrameP->framePort->portPixMap)->pixelSize == 8);
    SW_ASSERT((*dstFrameP->framePort->portPixMap)->pixelSize == 8);

    BP_CLIP_RECT((&dstFrameP->frameRect), srcBlitRect, dstBlitRect);
    START_32_BIT_MODE

    startRow = dstBlitRect.top / SWLitSquareSize;
    startCol = dstBlitRect.left / SWLitSquareSize;
    endRow = (dstBlitRect.bottom / SWLitSquareSize) + 1 ;
    endCol = (dstBlitRect.right / SWLitSquareSize) + 1;

    startSrcRow = srcBlitRect.top / SWLitSquareSize;
    startSrcCol = srcBlitRect.left / SWLitSquareSize;

    for (row = startRow, srcRow = startSrcRow; row <= endRow; row++, srcRow++) {
        for (col = startCol, srcCol = startSrcCol; col <= endCol; col++, srcCol++) {
            index = ((row * gLightingSquareColumns) + col);
            tableAtLevelAndIndex = &g8BitTranslucencyTable[(gLitSquareLevelTable[index] << 16) | (gLitSquareColorTable[index] << 8)];

            curSrcBlitRect.top = srcRow * SWLitSquareSize;
            curSrcBlitRect.bottom = curSrcBlitRect.top + SWLitSquareSize;
            curSrcBlitRect.left = srcCol * SWLitSquareSize;
            curSrcBlitRect.right = curSrcBlitRect.left + SWLitSquareSize;
            curDstBlitRect.top = row * SWLitSquareSize;
            curDstBlitRect.bottom = curDstBlitRect.top + SWLitSquareSize;
            curDstBlitRect.left = col * SWLitSquareSize;
            curDstBlitRect.right = curDstBlitRect.left + SWLitSquareSize;

            SectRect(&dstBlitRect, &curDstBlitRect, &curDstBlitRect);
            SectRect(&srcBlitRect, &curSrcBlitRect, &curSrcBlitRect);

                // calculate the number of bytes in each row to be copied
            numBytesPerRow = (curDstBlitRect.right - curDstBlitRect.left);

            BlitPixieLit8Bit(
                    // calculate the address of the first byte of the source
                (unsigned long *)(srcFrameP->frameBaseAddr +
                    (srcFrameP->scanLinePtrArray[curSrcBlitRect.top - srcFrameP->frameRect.top]) +
                    curSrcBlitRect.left),

                    // calculate the address of the first byte of the destination
                (unsigned long *)(dstFrameP->frameBaseAddr +
                    (dstFrameP->scanLinePtrArray[curDstBlitRect.top]) + curDstBlitRect.left),

                    // calculate the number of rows to blit
                curDstBlitRect.bottom - curDstBlitRect.top,

                    // number of bytes in a row (also the number of pixels to be copied)
                numBytesPerRow,

                srcFrameP->frameRowBytes,
                dstFrameP->frameRowBytes,
                tableAtLevelAndIndex
                );
        }
    }

    END_32_BIT_MODE
}

///--------------------------------------------------------------------------------------
//        LightingConvertChar
///--------------------------------------------------------------------------------------

SW_FUNC unsigned char SWInline LightingConvertChar (
    register unsigned char srcPixel,
    register unsigned char *tableAtLevelAndIndex) {

    // Easy, just the pixel in the table
    return tableAtLevelAndIndex[srcPixel];
}


///--------------------------------------------------------------------------------------
//        LightingConvertShort
///--------------------------------------------------------------------------------------

SW_FUNC unsigned short  LightingConvertShort (
    register unsigned short srcPixel,
    register unsigned char *tableAtLevelAndIndex) {

    register unsigned long colorValue;
    register unsigned long result = 0L;

    colorValue = tableAtLevelAndIndex[srcPixel >> 8];
    result = colorValue << 8;
    colorValue = tableAtLevelAndIndex[(srcPixel  & 0x00FF)];
    result = colorValue | result;
    return result;
}

#if USE_PPC_ASSEMBLY && __MWERKS__ >= 0x1800    // Only compiles under CW Pro

///--------------------------------------------------------------------------------------
//        LightingConvertLong
///--------------------------------------------------------------------------------------

SW_FUNC unsigned long  LightingConvertLong (
    register unsigned long srcPixel,
    register unsigned char *tableAtLevelAndIndex) {

    register unsigned long colorValue;
    register unsigned long result;

    colorValue = tableAtLevelAndIndex[srcPixel >> 24];    // look up the colored pixel
    result = colorValue << 24;                            // and shift it back into place as our high end pixel
    colorValue = tableAtLevelAndIndex[((srcPixel >> 16)  & 0x000000FF)];
    __rlwimi(    result, colorValue, 16, 8, 15    );
    colorValue = tableAtLevelAndIndex[((srcPixel >> 8)  & 0x000000FF)];
    __rlwimi(    result, colorValue, 8, 16, 23    );
    colorValue = tableAtLevelAndIndex[(srcPixel  & 0x000000FF)];
    __rlwimi(    result, colorValue, 0, 24, 31    );

    // return the four pixels we've computed
    return result;
}

#else /* USE_PPC_ASSEMBLY && __MWERKS__ >= 0x1800 */

///--------------------------------------------------------------------------------------
//        LightingConvertLong
///--------------------------------------------------------------------------------------

SW_FUNC unsigned long SWInline LightingConvertLong (
    register unsigned long srcPixel,
    register unsigned char *tableAtLevelAndIndex) {

    register unsigned long colorValue;
    register unsigned long result = 0L;

    colorValue = tableAtLevelAndIndex[srcPixel >> 24];    // look up the colored pixel
    result = colorValue << 24;                            // and shift it back into place as our high end pixel
    colorValue = tableAtLevelAndIndex[((srcPixel >> 16)  & 0x000000FF)];
    result = (colorValue << 16) | result;
    colorValue = tableAtLevelAndIndex[((srcPixel >> 8)  & 0x000000FF)];
    result = (colorValue << 8) | result;
    colorValue = tableAtLevelAndIndex[(srcPixel  & 0x000000FF)];
    result = colorValue | result;

    // return the four pixels we've computed
    return result;
}

#endif /* USE_PPC_ASSEMBLY */

///--------------------------------------------------------------------------------------
//        BlitPixieLit8Bit
///--------------------------------------------------------------------------------------


SW_FUNC void BlitPixieLit8Bit(
    unsigned long *srcPixelP,
    unsigned long *dstPixelP,
    register unsigned long rowsToCopy,
    register unsigned long numBytesPerRow,
    register unsigned long srcOffset,
    register unsigned long dstOffset,
    register unsigned char *tableAtLevelAndIndex)
{
    register long index;
    register unsigned long *startSrcPixelP;
    register unsigned long *startDstPixelP;


    startSrcPixelP = srcPixelP;
    startDstPixelP = dstPixelP;

    while (rowsToCopy--)
    {
        register fourblits = (numBytesPerRow >> 2);

        srcPixelP = startSrcPixelP;
        dstPixelP = startDstPixelP;

        for (index = 0; index < fourblits; index++) {
            dstPixelP[index] = LightingConvertLong(srcPixelP[index], tableAtLevelAndIndex);
        }

        srcPixelP += fourblits;
        dstPixelP += fourblits;

#ifdef MWERKS
        if (numBytesPerRow & 0x2)
            *((unsigned short *) dstPixelP)++ = LightingConvertShort(*((unsigned short *) srcPixelP)++, tableAtLevelAndIndex);
        if (numBytesPerRow & 0x1)
            *((unsigned char *) dstPixelP)++ = LightingConvertChar(*((unsigned char *) srcPixelP)++, tableAtLevelAndIndex);
#else
        if (numBytesPerRow & 0x2)
        {
                // Work around Think C's inability to do simple typecasting - Vern
            *(unsigned short *)dstPixelP = LightingConvertShort(*(unsigned short *)srcPixelP, tableAtLevelAndIndex);
            srcPixelP = (unsigned long *)(((unsigned short *)srcPixelP) + 1);
            dstPixelP = (unsigned long *)(((unsigned short *)dstPixelP) + 1);
        }
        if (numBytesPerRow & 0x1)
        {
            *(unsigned char *)dstPixelP = LightingConvertChar(*(unsigned char *)srcPixelP, tableAtLevelAndIndex);
            srcPixelP = (unsigned long *)(((unsigned char *)srcPixelP) + 1);
            dstPixelP = (unsigned long *)(((unsigned char *)dstPixelP) + 1);
        }
#endif

            // bump to next row
#ifdef MWERKS
        (char *)startSrcPixelP += srcOffset;
        (char *)startDstPixelP += dstOffset;
#else
        startSrcPixelP = (unsigned long *)(((char *)startSrcPixelP) + srcOffset);
        startDstPixelP = (unsigned long *)(((char *)startDstPixelP) + dstOffset);
#endif
    }
}

///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------
///--------------------------------------------------------------------------------------
/// 16 Bit Versions

#pragma mark ----------- 16 Bit Screen Draw Function -------------
///--------------------------------------------------------------------------------------
//        BlitPixie16BitLitRectDrawProc
///--------------------------------------------------------------------------------------

SW_FUNC void BlitPixie16BitLitRectDrawProc(
    FramePtr srcFrameP,
    FramePtr dstFrameP,
    Rect* srcRect,
    Rect* dstRect
    )
{
    Rect                     srcBlitRect = *srcRect;
    Rect                     dstBlitRect = *dstRect;
    unsigned long             numBytesPerRow;
    int                     startRow, endRow, startCol, endCol, startSrcRow, startSrcCol;
    int                     row, col, index, srcRow, srcCol;
    Rect                     curSrcBlitRect, curDstBlitRect;

    SW_ASSERT(srcFrameP->isFrameLocked && dstFrameP->isFrameLocked);
    SW_ASSERT((*srcFrameP->framePort->portPixMap)->pixelSize == 16);
    SW_ASSERT((*dstFrameP->framePort->portPixMap)->pixelSize == 16);

    BP_CLIP_RECT((&dstFrameP->frameRect), srcBlitRect, dstBlitRect);
    START_32_BIT_MODE

    startRow = dstBlitRect.top / SWLitSquareSize;
    startCol = dstBlitRect.left / SWLitSquareSize;
    endRow = (dstBlitRect.bottom / SWLitSquareSize) + 1 ;
    endCol = (dstBlitRect.right / SWLitSquareSize) + 1;

    startSrcRow = srcBlitRect.top / SWLitSquareSize;
    startSrcCol = srcBlitRect.left / SWLitSquareSize;

    for (row = startRow, srcRow = startSrcRow; row <= endRow; row++, srcRow++ ) {
        for (col = startCol, srcCol = startSrcCol; col <= endCol; col++, srcCol++ ) {
            index = ((row * gLightingSquareColumns) + col);

            curSrcBlitRect.top = srcRow * SWLitSquareSize;
            curSrcBlitRect.bottom = curSrcBlitRect.top + SWLitSquareSize;
            curSrcBlitRect.left = srcCol * SWLitSquareSize;
            curSrcBlitRect.right = curSrcBlitRect.left + SWLitSquareSize;
            curDstBlitRect.top = row * SWLitSquareSize;
            curDstBlitRect.bottom = curDstBlitRect.top + SWLitSquareSize;
            curDstBlitRect.left = col * SWLitSquareSize;
            curDstBlitRect.right = curDstBlitRect.left + SWLitSquareSize;

            SectRect(&dstBlitRect, &curDstBlitRect, &curDstBlitRect);
            SectRect(&srcBlitRect, &curSrcBlitRect, &curSrcBlitRect);

            numBytesPerRow = curDstBlitRect.right - curDstBlitRect.left;

            if (numBytesPerRow > 0)  // don't draw when the intersection is null...
                BlitPixieLit16Bit(
                        // calculate the address of the first byte of the source
                    (unsigned short *)(srcFrameP->frameBaseAddr +

    (srcFrameP->scanLinePtrArray[curSrcBlitRect.top - srcFrameP->frameRect.top]) +
                        (curSrcBlitRect.left << 1)),

                        // calculate the address of the first byte of the destination
                    (unsigned short *)(dstFrameP->frameBaseAddr +

    (dstFrameP->scanLinePtrArray[curDstBlitRect.top]) +
                        (curDstBlitRect.left << 1)),

                        // number of bytes in a row (also the number of pixels to be copied)
                    numBytesPerRow,
                    curDstBlitRect.bottom - curDstBlitRect.top,

                    srcFrameP->frameRowBytes,
                    dstFrameP->frameRowBytes,
                    gLitSquareColorTable[index],
                    gLitSquareLevelTable[index]
                    );
        }
    }

    END_32_BIT_MODE
}

#if USE_PPC_ASSEMBLY

// Some defines to make this easier to read
#define lookup_offset1 alpha
#define lookup_offset2 r11
#define lookup_offset3 r12
#define tablePointer r13
#define tmp1 r0
#define tmp2 r31
#define tmp3 r30

void asm BlitPixieLit16Bit(
    register unsigned short *srcPtr,
    register unsigned short *dstPtr,
    register unsigned long width,
    register unsigned long height,
    register unsigned long srcRowBytes,
    register unsigned long dstRowBytes,
    register unsigned long color,
    register unsigned long alpha)
{
    stw     tmp2,-4(SP)    //store temp vars on the stack
    stw     tmp3,-8(SP)
    stw     lookup_offset2,-12(SP)
    stw     lookup_offset3,-16(SP)
    stw     tablePointer,-20(SP)

    // Load a register with a pointer to our table
    lwz      tablePointer, g16BitTranslucencyTable(RTOC)
    lwz      tablePointer, 0(tablePointer)

    // We need to make the rowBytes be rowBytes - width because we are using
    // preincrements when getting and setting the pixels
    add        tmp1, width, width                //adjust for pixels being 2 bytes long
    sub        srcRowBytes,srcRowBytes,tmp1    //calculateoffsets to the next row
    sub        dstRowBytes,dstRowBytes,tmp1

    //adjust the pointers so we can use pre-increments
    subi    srcPtr,srcPtr,2
    subi    dstPtr,dstPtr,2

    // Set up the offsets into the blending table for each of our R, G, and B lookups
    // by setting the high order five bits to the alpha color
    // Note that these high order bits never get changed as we
    // work on our pixels, so the alpha (translucency level)
    // stays the same
    rlwinm    lookup_offset3,alpha,10,17,21
    mr        lookup_offset2,lookup_offset3
    mr        lookup_offset1,lookup_offset3

    rlwimi    lookup_offset3, color, 5, 22, 26        //blue channel source
    rlwimi    lookup_offset2, color, 0, 22, 26        //green channel source
    rlwimi    lookup_offset1, color, 27, 22, 26    //red channel source


@yloop
    mtctr     width                                    //set the ctr to so we copy do WIDTH number of pixels

        @xloop
            lhzu    tmp1,2(srcPtr)                    //load the source and destination colour

            rlwimi    lookup_offset3,tmp1,0,27,31        //blue channel destination
            rlwimi    lookup_offset2,tmp1,27,27,31    //green channel destination
            rlwimi    lookup_offset1,tmp1,22,27,31    //red channel destination

            lbzx    tmp3,tablePointer,lookup_offset3    //load blended blue channel
            lbzx    tmp2,tablePointer,lookup_offset2    //load blended green channel
            lbzx    tmp1,tablePointer,lookup_offset1    //load blended red channel

            rlwimi    tmp3,tmp2,5,22,26                //insert green channel into result
            rlwimi    tmp3,tmp1,10,17,21                //insert red channel into result

            sthu    tmp3,2(dstPtr)                    //store result

        @endOfBlitXLoop
            bdnz    @xloop                            // decrement the ctr and see if we're done

    // Now we move the pointers forward to the next row
    add        srcPtr,srcPtr,srcRowBytes
    add        dstPtr,dstPtr,dstRowBytes

    //and if we haven't finished, continue
    subi    height,height,1
    cmpwi    height,0
    bne        @yloop

    lwz     tmp2,-4(SP)            //clean up, restore registers we've been using
    lwz     tmp3,-8(SP)
    lwz     lookup_offset2,-12(SP)
    lwz     lookup_offset3,-16(SP)
    lwz     tablePointer,-20(SP)

    blr

}

#undef lookup_offset1
#undef lookup_offset2
#undef lookup_offset3
#undef tmp1
#undef tmp2
#undef tmp3
#undef height
#undef width

#else /* USE_PPC_ASSEMBLY */

// Here is a C version of the above function.
// it's about 20% slower than the assembly one.

// Note: don't declare the args to this function as "register".  If you do, then
// it won't compile properly for the 68K.

void BlitPixieLit16Bit (
     unsigned short *srcPtr,
     unsigned short *dstPtr,
     unsigned long width,
     unsigned long height,
     unsigned long srcRowBytes,
     unsigned long dstRowBytes,
     unsigned long color,
     unsigned long alpha) {

     int xx, yy;
     unsigned long lookup_offset_blue, lookup_offset_green, lookup_offset_red;
     unsigned long final_red, final_green, final_result;
    short curSource;

    srcRowBytes -= width * 2;
    dstRowBytes -= width * 2;

    lookup_offset_blue = lookup_offset_green = lookup_offset_red = alpha << 10;
    lookup_offset_blue |= (color << 5) & 0x03E0;
    lookup_offset_green |= color & 0x03E0;
    lookup_offset_red |= (color >> 5) & 0x03E0;

    for (yy = 0; yy < height; yy++) {
        for (xx = 0; xx < width; xx++) {
            curSource = *srcPtr++;

            lookup_offset_blue &= 0xFFE0;
            lookup_offset_green &= 0xFFE0;
            lookup_offset_red &= 0xFFE0;

            lookup_offset_blue |= curSource & 0x001F;
            lookup_offset_green |= (curSource >> 5) & 0x001F;
            lookup_offset_red |= (curSource >> 10) & 0x001F;

            final_red = g16BitTranslucencyTable[lookup_offset_red];
            final_green = g16BitTranslucencyTable[lookup_offset_green];
            final_result = g16BitTranslucencyTable[lookup_offset_blue];

            final_result |= final_green << 5;
            final_result |= final_red << 10;

            *dstPtr++ = final_result;
        }

#ifdef MWERKS
        (char *)srcPtr += srcRowBytes;
        (char *)dstPtr += dstRowBytes;
#else
        srcPtr = (unsigned short *)(((char *)srcPtr) + srcRowBytes);
        dstPtr = (unsigned short *)(((char *)dstPtr) + dstRowBytes);
#endif
    }

}
#endif /* USE_PPC_ASSEMBLY */