dxx-rebirth/common/texmap/scanline.cpp

/*
 * Portions of this file are copyright Rebirth contributors and licensed as
 * described in COPYING.txt.
 * Portions of this file are copyright Parallax Software and licensed
 * according to the Parallax license below.
 * See COPYING.txt for license details.

THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
SOFTWARE CORPORATION ("PARALLAX").  PARALLAX, IN DISTRIBUTING THE CODE TO
END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
IN USING, DISPLAYING,  AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
FREE PURPOSES.  IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES.  THE END-USER UNDERSTANDS
AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
*/

/*
 *
 * Routines to draw the texture mapped scanlines.
 *
 */

#include <math.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "maths.h"
#include "gr.h"
#include "grdef.h"
#include "texmap.h"
#include "texmapl.h"
#include "scanline.h"
#include "strutil.h"
#include "dxxerror.h"

namespace dcx {

tmap_scanline_function_table tmap_scanline_functions;

void c_tmap_scanline_flat()
{
	uint8_t *dest;
        int x, index = fx_xleft + (bytes_per_row * fx_y );

	dest = (write_buffer + fx_xleft + (bytes_per_row * fx_y ));

	for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
		if (++index >= SWIDTH*SHEIGHT) return;
		*dest++ = tmap_flat_color;
	}
//         memset(dest,tmap_flat_color,fx_xright-fx_xleft+1);
}

void c_tmap_scanline_shaded(const uint_fast32_t fade)
{
	uint8_t tmp;
	int x, index = fx_xleft + (bytes_per_row * fx_y );

	auto dest = &write_buffer[fx_xleft + (bytes_per_row * fx_y)];
	for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
		if (++index >= SWIDTH*SHEIGHT) return;
		tmp = *dest;
		*dest++ = gr_fade_table[fade][tmp];
	}
}

void c_tmap_scanline_lin_nolight()
{
	uint c;
	int x, index = fx_xleft + (bytes_per_row * fx_y );
	fix u,v,dudx, dvdx;

	u = fx_u;
	v = fx_v*64;
	dudx = fx_du_dx; 
	dvdx = fx_dv_dx*64; 

	auto dest = &write_buffer[fx_xleft + (bytes_per_row * fx_y)];

	if (!Transparency_on)	{
		for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
			if (++index >= SWIDTH*SHEIGHT) return;
			*dest++ = static_cast<uint32_t>(pixptr[ (f2i(v)&(64*63)) + (f2i(u)&63) ]);
			u += dudx;
			v += dvdx;
		}
	} else {
		for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
			if (++index >= SWIDTH*SHEIGHT) return;
			c = static_cast<uint32_t>(pixptr[ (f2i(v)&(64*63)) + (f2i(u)&63) ]);
			if ( c!=255)
				*dest = c;
			dest++;
			u += dudx;
			v += dvdx;
		}
	}
}

void c_tmap_scanline_lin()
{
	uint c;
	int x, j, index = fx_xleft + (bytes_per_row * fx_y);
	fix u,v,l,dudx, dvdx, dldx;

	u = fx_u;
	v = fx_v*64;
	dudx = fx_du_dx; 
	dvdx = fx_dv_dx*64; 

	l = fx_l>>8;
	dldx = fx_dl_dx/256;
	auto dest = &write_buffer[fx_xleft + (bytes_per_row * fx_y)];

	if (!Transparency_on)	{
		const auto pixPtrLocalCopy = pixptr;
		auto &fadeTableLocalCopy = gr_fade_table;

		x = fx_xright-fx_xleft+1;

		if ((j = reinterpret_cast<uintptr_t>(dest) & 3) != 0)
			{
			j = 4 - j;

			if (j > x)
				j = x;

			while (j > 0)
				{	
				if (++index >= SWIDTH*SHEIGHT) return;
				//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
				*dest++ = fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ (f2i(v)&(64*63)) + (f2i(u)&63) ] ];
				//end edit -MM
				l += dldx;
				u += dudx;
				v += dvdx;
				x--;
				j--;
				}
			}

		j &= ~3;
		while (j > 0)
			{
				uint32_t destlong;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong = fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ (f2i(v)&(64*63)) + (f2i(u)&63) ] ] << 24;
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong |= fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ (f2i(v)&(64*63)) + (f2i(u)&63) ] ] << 16;
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong |= fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ (f2i(v)&(64*63)) + (f2i(u)&63) ] ] << 8;
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong |= fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ (f2i(v)&(64*63)) + (f2i(u)&63) ] ];
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			*reinterpret_cast<uint32_t *>(dest) = destlong;
			dest += 4;
			x -= 4;
			j -= 4;
			index += 4;
			if (index+4 >= SWIDTH*SHEIGHT) return;
			}

		while (x-- > 0)
			{
			if (++index >= SWIDTH*SHEIGHT) return;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			*dest++ = fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ (f2i(v)&(64*63)) + (f2i(u)&63) ] ];
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			}

	} else {
		for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
			if (++index >= SWIDTH*SHEIGHT) return;
			c = static_cast<uint32_t>(pixptr[ (f2i(v)&(64*63)) + (f2i(u)&63) ]);
			if ( c!=TRANSPARENCY_COLOR)
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
				*dest = gr_fade_table[(l >> 8)&0x7f][c];
			//end edit -MM
			dest++;
			l += dldx;
			u += dudx;
			v += dvdx;
		}
	}
}

// This texture mapper uses floating point extensively and writes 8 pixels at once, so it likely works
// best on 64 bit RISC processors.
// WARNING: it is not endian clean. For big endian, reverse the shift counts in the unrolled loops. I
// have no means to test that, so I didn't try it. Please tell me if you get this to work on a big
// endian machine.
// If you're using an Alpha, use the Compaq compiler for this file for quite some fps more.
// Unfortunately, it won't compile the whole source, so simply compile everything, change the
// compiler to ccc, remove scanline.o and compile again.
// Please send comments/suggestions to falk.hueffner@student.uni-tuebingen.de.
static void c_fp_tmap_scanline_per()
{
	uint            c;
	int             x, j, index = fx_xleft + (bytes_per_row * fx_y);
	double          u, v, z, l, dudx, dvdx, dzdx, dldx, rec_z;

	u = f2db(fx_u);
	v = f2db(fx_v) * 64.0;
	z = f2db(fx_z);
	l = f2db(fx_l);
	dudx = f2db(fx_du_dx);
	dvdx = f2db(fx_dv_dx) * 64.0;
	dzdx = f2db(fx_dz_dx);
	dldx = f2db(fx_dl_dx);

	rec_z = 1.0 / z; // gcc 2.95.2 is won't do this optimization itself

	auto dest = &write_buffer[fx_xleft + (bytes_per_row * fx_y)];
	x = fx_xright - fx_xleft + 1;

	if (!Transparency_on) {
		if (x >= 8) {
			if ((j = reinterpret_cast<uintptr_t>(dest) & 7) != 0) {
				j = 8 - j;

				while (j > 0) {
					if (++index >= SWIDTH*SHEIGHT) return;
					*dest++ =
					    gr_fade_table[static_cast<int>(fabs(l))][
							  pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									((static_cast<int>(u * rec_z)) & 63)]];
					l += dldx;
					u += dudx;
					v += dvdx;
					z += dzdx;
					rec_z = 1.0 / z;
					x--;
					j--;
				}
			}

			j = x;
			while (j >= 8) {
				uint64_t destlong =
				    gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]];
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 8;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 16;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 24;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 32;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 40;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 48;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				destlong |=
				    static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][
							      pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) +
									    ((static_cast<int>(u * rec_z)) & 63)]]) << 56;
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;

				*(reinterpret_cast<uint64_t *>(dest)) = destlong;
				dest += 8;
				x -= 8;
				j -= 8;
				index += 8;
				if (index+8 >= SWIDTH*SHEIGHT) return;
			}
		}
		while (x-- > 0) {
			if (++index >= SWIDTH*SHEIGHT) return;
			*dest++ =
			    gr_fade_table[static_cast<int>(fabs(l))][
					  static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)])];
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			rec_z = 1.0 / z;
		}
	} else {
		if (x >= 8) {
			if ((j = reinterpret_cast<uintptr_t>(dest) & 7) != 0) {
				j = 8 - j;

				while (j > 0) {
					if (++index >= SWIDTH*SHEIGHT) return;
					c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
					if (c != 255)
						*dest = gr_fade_table[static_cast<int>(fabs(l))][c];
					dest++;
					l += dldx;
					u += dudx;
					v += dvdx;
					z += dzdx;
					rec_z = 1.0 / z;
					x--;
					j--;
				}
			}

			j = x;
			while (j >= 8) {
				uint64_t destlong;
				destlong = *(reinterpret_cast<uint64_t *>(dest));
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~static_cast<uint64_t>(0xFF);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]);
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 8);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 8;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 16);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 16;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 24);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 24;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 32);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 32;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 40);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 40;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 48);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 48;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;
				c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
				if (c != 255) {
					destlong &= ~(static_cast<uint64_t>(0xFF) << 56);
					destlong |= static_cast<uint64_t>(gr_fade_table[static_cast<int>(fabs(l))][c]) << 56;
				}
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				rec_z = 1.0 / z;

				*(reinterpret_cast<uint64_t *>(dest)) = destlong;
				dest += 8;
				x -= 8;
				j -= 8;
				index += 8;
				if (index+8 >= SWIDTH*SHEIGHT) return;
			}
		}
		while (x-- > 0) {
			if (++index >= SWIDTH*SHEIGHT) return;
			c = static_cast<uint32_t>(pixptr[((static_cast<int>(v * rec_z)) & (64 * 63)) + ((static_cast<int>(u * rec_z)) & 63)]);
			if (c != 255)
				*dest = gr_fade_table[static_cast<int>(fabs(l))][c];
			dest++;
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			rec_z = 1.0 / z;
		}
	}
}

// note the unrolling loop is broken. It is never called, and uses big endian. -- FH
static void c_tmap_scanline_per()
{
	uint c;
	int x, j, index = fx_xleft + (bytes_per_row * fx_y);
	fix l,u,v,z;
	fix dudx, dvdx, dzdx, dldx;

	u = fx_u;
	v = fx_v*64;
	z = fx_z;
	dudx = fx_du_dx; 
	dvdx = fx_dv_dx*64; 
	dzdx = fx_dz_dx;

	l = fx_l>>8;
	dldx = fx_dl_dx/256;
	auto dest = &write_buffer[fx_xleft + (bytes_per_row * fx_y)];

	if (!Transparency_on)	{
		const auto pixPtrLocalCopy = pixptr;
		auto &fadeTableLocalCopy = gr_fade_table;

		x = fx_xright-fx_xleft+1; // x = number of pixels in scanline

		if ((j = reinterpret_cast<uintptr_t>(dest) & 3) != 0)
			{
			j = 4 - j;

			if (j > x)
				j = x;

			while (j > 0)
				{	
				if (++index >= SWIDTH*SHEIGHT) return;
				//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
				*dest++ = fadeTableLocalCopy[(l>>8)&0x7f][static_cast<uint32_t>(pixPtrLocalCopy[ ( (v/z)&(64*63) ) + ((u/z)&63) ]) ];
				//end edit -MM
				l += dldx;
				u += dudx;
				v += dvdx;
				z += dzdx;
				x--;
				j--;
				}
			}

		j &= ~3;
		while (j > 0)
			{
				uint32_t destlong;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong = fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ ( (v/z)&(64*63) ) + ((u/z)&63) ] ] << 24;
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong |= fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ ( (v/z)&(64*63) ) + ((u/z)&63) ] ] << 16;
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong |= fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ ( (v/z)&(64*63) ) + ((u/z)&63) ] ] << 8;
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			destlong |= fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ ( (v/z)&(64*63) ) + ((u/z)&63) ] ];
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			*reinterpret_cast<uint32_t *>(dest) = destlong;
			dest += 4;
			x -= 4;
			j -= 4;
			index += 4;
			if (index+4 >= SWIDTH*SHEIGHT) return;
			}

		while (x-- > 0)
			{
			if (++index >= SWIDTH*SHEIGHT) return;
			//edited 05/18/99 Matt Mueller - changed from 0xff00 to 0x7f00 to fix glitches
			*dest++ = fadeTableLocalCopy[(l>>8)&0x7f][pixPtrLocalCopy[ ( (v/z)&(64*63) ) + ((u/z)&63) ] ];
			//end edit -MM
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
			}

	} else {
		for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
			if (++index >= SWIDTH*SHEIGHT) return;
			c = static_cast<uint32_t>(pixptr[ ( (v/z)&(64*63) ) + ((u/z)&63) ]);
			if ( c!=TRANSPARENCY_COLOR)
				*dest = gr_fade_table[(l >> 8) &0x7f][c ];
			dest++;
			l += dldx;
			u += dudx;
			v += dvdx;
			z += dzdx;
		}
	}
}

static void c_tmap_scanline_quad()
{
	uint c;
	int x, index = fx_xleft + (bytes_per_row * fx_y);
	fix u,v,l,dudx, dvdx, dldx;

	// Quadratic setup stuff:
	fix a1, a2, b1, b2, dudx1, dvdx1;
	fix u0 = fx_u;
	fix u2 = fx_u + fx_du_dx*(fx_xright-fx_xleft+1);	// This just needs to be uright from outer loop
	fix v0 = fx_v;
	fix v2 = fx_v + fx_dv_dx*(fx_xright-fx_xleft+1);	// This just needs to be vright from outer loop
	fix w0 = fx_z;
	fix w2 = fx_z + fx_dz_dx*(fx_xright-fx_xleft+1);	// This just needs to be zright from outer loop
	fix u1 = fixdiv((u0+u2),(w0+w2));						
	fix v1 = fixdiv((v0+v2),(w0+w2));
	int dx = fx_xright-fx_xleft+1;		
	u0 = fixdiv( u0, w0 );	// Divide Z out.  This should be in outer loop
	v0 = fixdiv( v0, w0 );	// Divide Z out.  This should be in outer loop
	u2 = fixdiv( u2, w2 );	// Divide Z out.  This should be in outer loop
	v2 = fixdiv( v2, w2 );	// Divide Z out.  This should be in outer loop
	a1 = (-3*u0+4*u1-u2)/dx;			
	b1 = (-3*v0+4*v1-v2)/dx;
	a2 = (2*(u0-2*u1+u2))/(dx*dx);	
	b2 = (2*(v0-2*v1+v2))/(dx*dx);
	dudx = a1 + a2;
	dvdx = b1 + b2;
	dudx1 = 2*a2;
	dvdx1 = 2*b2;
	u = u0;
	v = v0;

	// Normal lighting setup
	l = fx_l>>8;
	dldx = fx_dl_dx>>8;
	
	// Normal destination pointer setup
	auto dest = &write_buffer[fx_xleft + (bytes_per_row * fx_y)];

	if (!Transparency_on)	{
		for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
			if (++index >= SWIDTH*SHEIGHT) return;
			*dest++ = gr_fade_table[(l>>8)&0xff][pixptr[  (f2i(v)&63)*64 + (f2i(u)&63) ] ];
			l += dldx;
			u += dudx;
			v += dvdx;
			dudx += dudx1;		// Extra add for quadratic!
			dvdx += dvdx1;		// Extra add for quadratic!
		}
	} else {
		for (x= fx_xright-fx_xleft+1 ; x > 0; --x ) {
			if (++index >= SWIDTH*SHEIGHT) return;
			c = static_cast<uint32_t>(pixptr[  (f2i(v)&63)*64 + (f2i(u)&63) ]);
			if ( c!=255)
				*dest = gr_fade_table[(l>>8)&0xff][c];
			dest++;
			l += dldx;
			u += dudx;
			v += dvdx;
			dudx += dudx1;		// Extra add for quadratic!
			dvdx += dvdx1;		// Extra add for quadratic!
		}
	}
}

//runtime selection of optimized tmappers.  12/07/99  Matthew Mueller
//the reason I did it this way rather than having a *tmap_funcs that then points to a c_tmap or fp_tmap struct thats already filled in, is to avoid a second pointer dereference.
void select_tmap(const std::string &type)
{
	if (type == "fp")
	{
		cur_tmap_scanline_per=c_fp_tmap_scanline_per;
	}
	else if (type == "quad")
	{
		cur_tmap_scanline_per=c_tmap_scanline_quad;
	}
	else {
		cur_tmap_scanline_per=c_tmap_scanline_per;
	}
}

}