From:	qball1723 AT aol DOT com (QBall1723)
Newsgroups:	comp.os.msdos.djgpp
Subject:	DJGPP inline solution anyone?
Date:	13 Nov 1997 13:02:22 GMT
Lines:	227
Message-ID:	<19971113130201.IAA27637@ladder01.news.aol.com>
NNTP-Posting-Host:	ladder01.news.aol.com
Organization:	AOL http://www.aol.com
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hello All,

      I've just begun coding with DJGPP... and I'd like to get some input on
 converting a routine originally written for 16-bit REAL MODE Dos... to DJGPP's
 inline assembly....

     ... I may give TOO much information... but here goes.. (I'm including some
 declarations & support routines...)

     Thank you for reading this and trying to help me out!


********************* some declares

int *scale_table[MAX_SCALE+1];     // table with pre-computed scale indices

// parmeter block used by assembly language sliver engine

char *sliver_texture; // pointer to texture being rendered
int sliver_column;        // index into texture i.e. which column of texture
int sliver_top;           // starting Y position to render at
int sliver_bottom;
int sliver_scale;         // overall height of sliver
int sliver_ray;           // current ray being cast
int sliver_clip;          // index into texture after clipping
int *scale_row;           // row of scale value look up table to use

****************Here's the routine in question

void Render_Sliver(void)
{
	// this is yet another version of the sliver scaler, however it uses look up
	// tables with pre-computed scale indices.

	// this draws vertical slivers fromthe middle of the strip to the top,
	// and fromthe middle of the strip to the bottom.

	char *work_sprite;
	int *row;
   char *draw_from;
	int work_offset=0,offset,temp_offset,y_off,scale_off;

	// alias a pointer to sprite for ease of access

	work_sprite = sliver_texture;

	// compute offset of sprite in video buffer

	temp_offset = v_320[99] + sliver_ray;

	// render top half of wall sliver

	offset = temp_offset;

   draw_from = double_buffer + offset;

	work_offset = WALL_MIDDLE_OFFSET;

	*draw_from = work_sprite[work_offset+sliver_column];

	for (y_off=1; y_off<sliver_scale; y_off++)
    {

	    draw_from      -= 320;
	    work_offset =  WALL_MIDDLE_OFFSET - scale_row[y_off];

	    *draw_from = work_sprite[work_offset+sliver_column];

    } // end for y

	// render bottomhalf of wall sliver

	offset = temp_offset + 320;

   draw_from = double_buffer + offset;

	work_offset = WALL_MIDDLE_OFFSET;

	*draw_from = work_sprite[work_offset+sliver_column];

	for (y_off=0; y_off<(sliver_scale); y_off++)
    {


	    draw_from      += 320;
	    work_offset =  WALL_MIDDLE_OFFSET + scale_row[y_off];

	    *draw_from = work_sprite[work_offset+sliver_column];
    } // end for y

} // end Render_Sliver


*************allocation & initialization of scale_table
// create the lookup tables for the scaler
// there have the formof an array of pointers, where each pointer points
// another another array of data where the 'data' are the scale indices

	for (scale=0; scale<=100; scale++)
    {

    scale_table[scale] = (int *)malloc(scale*sizeof(int)+1);

    } // end for scale
	for (scale=101; scale<=MAX_SCALE; scale++)
    {

    scale_table[scale] = (int *)malloc((101)*sizeof(int)+1);

    } // end for scale

	// create tables, sit back for a sec!

	for (ang=ANGLE_0; ang<=ANGLE_360; ang++)
    {

// build the scaler table.  This table holds MAX_SCALE different arrays.  Each
// array consists of the pre-computed indices for an object to be scaled

	for (scale=1; scale<=99; scale++)
    {

	    // create the indices for this scale

	    Create_Scale_Data(scale, (int *)scale_table[scale]);

    } // end for scale

    // THE SECOND Create_Scale_Data FUNCTION REFERED TO HERE IS USED
    // TO COMPUTE SCALES FOR CASES WHERE THE BOTTOmAND THE TOP OF A WALL
    // SLIVER ARE BEYOND THE VERTICAL EXTENTS OF THE VIEWPORT!

	for (scale=99+1; scale<=MAX_SCALE; scale++)
    {

	    // create the indices for this scale

	    Create_Scale_Data2(scale, (int *)scale_table[scale]);

    } // end for scale


*******************************************

Initializers....


void Create_Scale_Data(int scaler, int *row)
{

// this function synthesizes the scaling of a texture sliver to all possible
// sizes and creates a huge look up table of the data.

int y_off;

float y_scale_index=0,
      y_scale_step;

// compute scale step or number of source pixels to map to destination/cycle

y_scale_step = (float)32/(float)scaler;

y_scale_index+=y_scale_step;

for (y_off=0; y_off<scaler; y_off++)
    {
    // place data into proper array position for later use

    row[y_off] = ((int)(y_scale_index+.4)) * SWATCH_WIDTH;

    // test if we slightly went overboard

    if  (row[y_off] > WALL_MIDDLE_OFFSET) row[y_off] = WALL_MIDDLE_OFFSET;

    // next index please

    y_scale_index+=y_scale_step;

    } // end for y_off

} // end Create_Scale_Data

void Create_Scale_Data2(int scaler, int *row)
{

// this function synthesizes the scaling of a texture sliver to all possible
// sizes and creates a huge look up table of the data.

// this adds data for cases where the vertical extents of the "sliver" are
// beyond the vertical extents of the viewport

int y_off;

float y_scale_index=0,
      y_scale_step;

// compute scale step or number of source pixels to map to destination/cycle

y_scale_step = (float)32/(float)scaler;

y_scale_index+=y_scale_step;

for (y_off=0; y_off<99+1; y_off++)
    {
    // place data into proper array position for later use

    row[y_off] = ((int)(y_scale_index+.3)) * SWATCH_WIDTH;

    // test if we slightly went overboard

    if  (row[y_off] > WALL_MIDDLE_OFFSET) row[y_off] = WALL_MIDDLE_OFFSET;

    // next index please

    y_scale_index+=y_scale_step;

    } // end for y_off

} // end Create_Scale_Data2


      Again - thanks for checking this out!


Jim the loiterer
http://members.aol.com/qball1723/index.htm
(I make games)

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