/***************************************************************************
* *
* Project64-video - A Nintendo 64 gfx plugin. *
* http://www.pj64-emu.com/ *
* Copyright (C) 2017 Project64. All rights reserved. *
* Copyright (C) 2003-2009 Sergey 'Gonetz' Lipski *
* Copyright (C) 2002 Dave2001 *
* *
* License: *
* GNU/GPLv2 http://www.gnu.org/licenses/gpl-2.0.html *
* version 2 of the License, or (at your option) any later version. *
* *
****************************************************************************/
#include "Gfx_1.3.h"
#include "rdp.h"
#include "DepthBufferRender.h"
uint16_t * zLUT = 0;
void ZLUT_init()
{
if (zLUT)
return;
zLUT = new uint16_t[0x40000];
for (int i = 0; i < 0x40000; i++)
{
uint32_t exponent = 0;
uint32_t testbit = 1 << 17;
while ((i & testbit) && (exponent < 7))
{
exponent++;
testbit = 1 << (17 - exponent);
}
uint32_t mantissa = (i >> (6 - (6 < exponent ? 6 : exponent))) & 0x7ff;
zLUT[i] = (uint16_t)(((exponent << 11) | mantissa) << 2);
}
}
void ZLUT_release()
{
delete[] zLUT;
zLUT = 0;
}
static vertexi * max_vtx; // Max y vertex (ending vertex)
static vertexi * start_vtx, *end_vtx; // First and last vertex in array
static vertexi * right_vtx, *left_vtx; // Current right and left vertex
static int right_height, left_height;
static int right_x, right_dxdy, left_x, left_dxdy;
static int left_z, left_dzdy;
__inline int imul16(int x, int y) // (x * y) >> 16
{
return ((int64_t)x * (int64_t)y) >> 16;
}
__inline int imul14(int x, int y) // (x * y) >> 14
{
return ((int64_t)x * (int64_t)y) >> 14;
}
__inline int idiv16(int x, int y) // (x << 16) / y
{
x = ((int64_t)x << 16) / (int64_t)y;
return x;
}
__inline int iceil(int x)
{
x += 0xffff;
return (x >> 16);
}
static void RightSection(void)
{
// Walk backwards trough the vertex array
vertexi * v2, *v1 = right_vtx;
if (right_vtx > start_vtx) v2 = right_vtx - 1;
else v2 = end_vtx; // Wrap to end of array
right_vtx = v2;
// v1 = top vertex
// v2 = bottom vertex
// Calculate number of scanlines in this section
right_height = iceil(v2->y) - iceil(v1->y);
if (right_height <= 0) return;
// Guard against possible div overflows
if (right_height > 1) {
// OK, no worries, we have a section that is at least
// one pixel high. Calculate slope as usual.
int height = v2->y - v1->y;
right_dxdy = idiv16(v2->x - v1->x, height);
}
else {
// Height is less or equal to one pixel.
// Calculate slope = width * 1/height
// using 18:14 bit precision to avoid overflows.
int inv_height = (0x10000 << 14) / (v2->y - v1->y);
right_dxdy = imul14(v2->x - v1->x, inv_height);
}
// Prestep initial values
int prestep = (iceil(v1->y) << 16) - v1->y;
right_x = v1->x + imul16(prestep, right_dxdy);
}
static void LeftSection(void)
{
// Walk forward trough the vertex array
vertexi * v2, *v1 = left_vtx;
if (left_vtx < end_vtx) v2 = left_vtx + 1;
else v2 = start_vtx; // Wrap to start of array
left_vtx = v2;
// v1 = top vertex
// v2 = bottom vertex
// Calculate number of scanlines in this section
left_height = iceil(v2->y) - iceil(v1->y);
if (left_height <= 0) return;
// Guard against possible div overflows
if (left_height > 1) {
// OK, no worries, we have a section that is at least
// one pixel high. Calculate slope as usual.
int height = v2->y - v1->y;
left_dxdy = idiv16(v2->x - v1->x, height);
left_dzdy = idiv16(v2->z - v1->z, height);
}
else {
// Height is less or equal to one pixel.
// Calculate slope = width * 1/height
// using 18:14 bit precision to avoid overflows.
int inv_height = (0x10000 << 14) / (v2->y - v1->y);
left_dxdy = imul14(v2->x - v1->x, inv_height);
left_dzdy = imul14(v2->z - v1->z, inv_height);
}
// Prestep initial values
int prestep = (iceil(v1->y) << 16) - v1->y;
left_x = v1->x + imul16(prestep, left_dxdy);
left_z = v1->z + imul16(prestep, left_dzdy);
}
void Rasterize(vertexi * vtx, int vertices, int dzdx)
{
start_vtx = vtx; // First vertex in array
// Search trough the vtx array to find min y, max y
// and the location of these structures.
vertexi * min_vtx = vtx;
max_vtx = vtx;
int min_y = vtx->y;
int max_y = vtx->y;
vtx++;
for (int n = 1; n < vertices; n++) {
if (vtx->y < min_y) {
min_y = vtx->y;
min_vtx = vtx;
}
else
if (vtx->y > max_y) {
max_y = vtx->y;
max_vtx = vtx;
}
vtx++;
}
// OK, now we know where in the array we should start and
// where to end while scanning the edges of the polygon
left_vtx = min_vtx; // Left side starting vertex
right_vtx = min_vtx; // Right side starting vertex
end_vtx = vtx - 1; // Last vertex in array
// Search for the first usable right section
do {
if (right_vtx == max_vtx) return;
RightSection();
} while (right_height <= 0);
// Search for the first usable left section
do {
if (left_vtx == max_vtx) return;
LeftSection();
} while (left_height <= 0);
uint16_t * destptr = (uint16_t*)(gfx.RDRAM + rdp.zimg);
int y1 = iceil(min_y);
if (y1 >= (int)rdp.scissor_o.lr_y) return;
int shift;
for (;;)
{
int x1 = iceil(left_x);
if (x1 < (int)rdp.scissor_o.ul_x)
x1 = rdp.scissor_o.ul_x;
int width = iceil(right_x) - x1;
if (x1 + width >= (int)rdp.scissor_o.lr_x)
width = rdp.scissor_o.lr_x - x1 - 1;
if (width > 0 && y1 >= (int)rdp.scissor_o.ul_y) {
// Prestep initial z
int prestep = (x1 << 16) - left_x;
int z = left_z + imul16(prestep, dzdx);
shift = x1 + y1*rdp.zi_width;
//draw to depth buffer
int trueZ;
int idx;
uint16_t encodedZ;
for (int x = 0; x < width; x++)
{
trueZ = z / 8192;
if (trueZ < 0) trueZ = 0;
else if (trueZ > 0x3FFFF) trueZ = 0x3FFFF;
encodedZ = zLUT[trueZ];
idx = (shift + x) ^ 1;
if (encodedZ < destptr[idx])
destptr[idx] = encodedZ;
z += dzdx;
}
}
//destptr += rdp.zi_width;
y1++;
if (y1 >= (int)rdp.scissor_o.lr_y) return;
// Scan the right side
if (--right_height <= 0) { // End of this section?
do {
if (right_vtx == max_vtx) return;
RightSection();
} while (right_height <= 0);
}
else
right_x += right_dxdy;
// Scan the left side
if (--left_height <= 0) { // End of this section?
do {
if (left_vtx == max_vtx) return;
LeftSection();
} while (left_height <= 0);
}
else {
left_x += left_dxdy;
left_z += left_dzdy;
}
}
}