167 tools/vis.c
View file
@@ -2,70 +2,19 @@
#include <stdio.h>
#include <math.h>

// clamp the value x to the range of 0..r

int clamp(int x, int r)
{
if (x < 0) return 0;
if (x > r) return r;
return x;
}

// generate assembly for the vis table
// the vistable is a 64 kbyte table which stores a precomputed visibility
// info byte for each combination of source and target lightel.

void vistable()
{
for(unsigned int i = 0; i < 256 * 256; ++i) {
if((i & 15) == 0) printf("\n.byte ");
if((i & 15) != 0) printf (", ");
int
from_vis = ((i >> 8) & 31) - 4,
to_vis = (i >> 4) & 15;

int new_vis;

new_vis = clamp(from_vis + to_vis * 2, 28) + 4;

printf("$%02x", new_vis);

}
printf("\n\n");
}
#define LIGHT_RADIUS 21

// assembly snippets for putting together an unrolled
// visibility computation loop

#define LIGHT_ASM \
"lda a:light_origin + $%04x\n" \
"xba\n" \
"lda a:light_origin + $%04x\n" \
"tax\n" \
"lda f:vistable + $%04x, x\n" \
"sta a:light_origin + $%04x\n\n" \

#define SHORT_LIGHT_ASM \
";lda a:light_origin + $%04x\n" \
";xba\n" \
"lda a:light_origin + $%04x\n" \
"tax\n" \
"lda f:vistable + $%04x, x\n" \
"sta a:light_origin + $%04x\n\n" \

#define COLUMN_ASM \
"cpy #$%02x\n" \
"%s :+\n" \
"jmp %s\n" \
":\n\n"

// radius of the light

#define RADIUS 23

// number of unrolled loops = BUFFERMAX + 1

#define BUFFERMAX 1
"%s\n" \
"adc a:visibility_origin + $%04x\n" \
"bmi :+\n" \
"jmp _end_tile_%04x\n" \
":\n" \
"sta a:light_origin + $%04x\n\n"

// get address of a lightel in the bufferpos

@@ -74,22 +23,19 @@ int bufferpos(int xx, int yy)
int p = xx + yy * 32 + 30 * 32;

// sanity check
if(p < 0) { printf("warning: buffer size check failed.\n"); }
if(p >= 32 * 64) { printf("warning : buffer size check failed.\n"); }
if(p < 0) { fprintf(stderr, "warning: buffer size check failed.\n"); }
if(p >= 32 * 64) { fprintf(stderr, "warning : buffer size check failed.\n"); }

return p;
}


// table for the maximum vertical extent
// of each visibility loop variation

int maxtable[] = { -16, 24, -24, 16 };
void tile(int xx, int yy);


// generate the assembly for a single lightel

void light(int xx, int yy, int overflow)
void light(int xx, int yy, int from_xx, int from_yy)
{
if(xx == 0 && yy == 0) return;

@@ -98,8 +44,6 @@ void light(int xx, int yy, int overflow)

int stable[] = { 0, 1, 1, 3, 1, 4, 3, 7, 1, 7, 4, 11, 3, 10, 7, 15, 1, 13, 9, 19, 5, 17, 11, 23 };

static int prevxxs = 255, prevyys = 255;

int xxabs = xx < 0 ? -xx : xx;
int yyabs = yy < 0 ? -yy : yy;

@@ -117,91 +61,76 @@ void light(int xx, int yy, int overflow)
} else xxs = xx;
}

if(xxs != from_xx || yys != from_yy) return;

// get distance from orgin

float rr = sqrtf(xx * xx + yy * yy);
float rrs = sqrtf(xxs * xxs + yys * yys);

int dest = bufferpos(xx, yy);

if(rr > RADIUS + 0.8f) {
if(!overflow) return;
else {
printf("lda #$ff\n");
printf("sta a:light_origin + $%04x\n", dest);
return;
}
}
if(rr > LIGHT_RADIUS) return;


printf((prevxxs == xxs && prevyys == yys) ? SHORT_LIGHT_ASM : LIGHT_ASM,
printf(LIGHT_ASM,
bufferpos(xxs, yys),
dest,
(int)(rr * 0.8f) == (int)(rrs * 0.8f) ? 0x0 : 0x100,
dest);
(int)(rr * 0.8f) == (int)(rrs * 0.8f) ? "clc" : "sec",
bufferpos(xxs, yys), yy * 256 + xx, dest);

tile(xx, yy); // recursively build the shadow cone

prevxxs = xxs;
prevyys = yys;
printf("_end_tile_%04x:\n", yy * 256 + xx);
}

void tile(int xx, int yy)
{
light(xx - 1, yy - 1, xx, yy);
light(xx , yy - 1, xx, yy);
light(xx + 1, yy - 1, xx, yy);
light(xx - 1, yy , xx, yy);
light(xx + 1, yy , xx, yy);
light(xx - 1, yy + 1, xx, yy);
light(xx , yy + 1, xx, yy);
light(xx + 1, yy + 1, xx, yy);
}

// generate a visibility computation loop

void cast(int ii)
// make a fence around the visibile area
// for aborting the loop
void fence()
{
printf("viscast_%i:\n", ii);

for(int xx = 0; xx >= -RADIUS; --xx) {
for(int yy = 0; yy >= -RADIUS; --yy)
if(yy >= maxtable[(BUFFERMAX - ii) * 2 + 0]) light(xx, yy, 0);
for(int yy = 1; yy <= RADIUS; ++yy)
if(yy < maxtable[(BUFFERMAX - ii) * 2 + 1]) light(xx, yy, 0);
if (xx > -RADIUS) printf(COLUMN_ASM, (32 + xx) * 2, "bmi", "@skip_1");
printf("lda #31\n");
for(int ii = 0; ii < 32; ++ii) {
printf("sta a:visibility_origin + $%04x, x\n", ii);
printf("sta a:visibility_origin + $%04x, x\n", ii + 32 * 29);
}

printf("@skip_1:\n\n");

for(int xx = 1; xx <= RADIUS; ++xx) {
for(int yy = 0; yy >= -RADIUS; --yy)
if(yy >= maxtable[(BUFFERMAX - ii) * 2 + 0]) light(xx, yy, 0);
for(int yy = 1; yy <= RADIUS; ++yy)
if(yy < maxtable[(BUFFERMAX - ii) * 2 + 1]) light(xx, yy, 0);
if (xx < RADIUS) printf(COLUMN_ASM, (xx + 2) * 2, "bpl", "_end");
for(int ii = 0; ii < 30; ++ii) {
printf("sta a:visibility_origin + $%04x, x\n", ii * 32);
printf("sta a:visibility_origin + $%04x, x\n", ii * 32 + 31);
}

printf("jmp _end\n\n");
}


// generate the visibility computation loop

int main()
{
printf(".export viscast\n");
printf(".import light_origin \n\n");
printf(".import visibility_origin \n\n");

printf(".segment \"code3\"\n\n");

printf("jumptable:\n\n");
printf(".word .loword(viscast_0)\n");
printf(".word .loword(viscast_1)\n");

printf("\nviscast:\n\n");
printf("lda #$7e\npha\nplb\n\n");
printf("jmp (.loword(jumptable), x)\n\n");
printf("_end:\n\n");
printf("lda #$80\npha\nplb\n\n");
printf("rtl\n\n");

for(int ii = 0; ii <= BUFFERMAX; ++ii) {
cast(ii);
}

printf("\n\n.segment \"vistable\"\n\n");

printf("\nvistable:\n");
fence();

vistable();
tile(0, 0);

printf("_end:\n\n");
printf("lda #$80\npha\nplb\n\n");
printf("rtl\n\n");

return 0;
};