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Added better rounding after division.

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This commit is contained in:
jespergravgaard 2021-04-03 21:00:48 +02:00
parent 9c9a99e2ac
commit 65eb2edc12
2 changed files with 14 additions and 10 deletions
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3
src/main/kc/include/mega65-math.h
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@ -18,6 +18,9 @@ char * const MATH_BUSY = 0xd70f;
// $D768-$D76F DIVOUT 64-bit output of MULTINA ÷ MULTINB
// $D768-$D76B DIVOUT FRAC 32-bit output of MULTINA ÷ MULTINB
signed char volatile * const MATH_DIVOUT_FRAC_CHAR0 = 0xd768;
signed char volatile * const MATH_DIVOUT_FRAC_CHAR1 = 0xd769;
signed char volatile * const MATH_DIVOUT_FRAC_CHAR2 = 0xd76a;
signed char volatile * const MATH_DIVOUT_FRAC_CHAR3 = 0xd76b;
signed int volatile * const MATH_DIVOUT_FRAC_INT0 = 0xd768;
signed int volatile * const MATH_DIVOUT_FRAC_INT1 = 0xd76a;
signed long volatile * const MATH_DIVOUT_FRAC_LONG0 = 0xd768;

21
src/test/kc/examples/mega65/linedrawing.c
View File

@ -216,9 +216,9 @@ void draw_line(int x1, int y1, int x2, int y2, unsigned char colour) {
y2 = temp;
}
// Use hardware divider to get the slope (add 1/2 to get better rounding )
*MATH_MULTINA_INT0 = dx*2+1;
*MATH_MULTINB_INT0 = dy*2;
// Use hardware divider to get the slope
*MATH_MULTINA_INT0 = dx;
*MATH_MULTINB_INT0 = dy;
*MATH_MULTINA_INT1 = 0;
*MATH_MULTINB_INT1 = 0;
@ -229,9 +229,9 @@ void draw_line(int x1, int y1, int x2, int y2, unsigned char colour) {
lda MATH_DIVOUT_FRAC_INT1 @nooptimize
lda MATH_DIVOUT_FRAC_INT1 @nooptimize
}
// Slope is the most significant bytes of the fractional part
// of the division result
unsigned int slope = (unsigned int)*MATH_DIVOUT_FRAC_INT1;
// Slope is the most significant bytes of the fractional part of the division result
// Perform rounding by examining the next bit also
unsigned int slope = (unsigned int)*MATH_DIVOUT_FRAC_INT1 + (((char)*MATH_DIVOUT_FRAC_CHAR1&0x80)?1:0);
unsigned int slope_init = 32768;
unsigned long addr = GRAPHICS + (unsigned int)(x1/8) * 64 * 25 + (unsigned int)(y1*8) + (unsigned char)(x1&7);
unsigned int count = (unsigned int)dy;
@ -249,9 +249,9 @@ void draw_line(int x1, int y1, int x2, int y2, unsigned char colour) {
y2 = temp;
}
// Use hardware divider to get the slope (add 1/2 to get better rounding )
*MATH_MULTINA_INT0 = dy*2+1;
*MATH_MULTINB_INT0 = dx*2;
// Use hardware divider to get the slope
*MATH_MULTINA_INT0 = dy;
*MATH_MULTINB_INT0 = dx;
*MATH_MULTINA_INT1 = 0;
*MATH_MULTINB_INT1 = 0;
@ -264,7 +264,8 @@ void draw_line(int x1, int y1, int x2, int y2, unsigned char colour) {
}
// Slope is the most significant bytes of the fractional part of the division result
unsigned int slope = (unsigned int)*MATH_DIVOUT_FRAC_INT1;
// Perform rounding by examining the next bit also
unsigned int slope = (unsigned int)*MATH_DIVOUT_FRAC_INT1 + (((char)*MATH_DIVOUT_FRAC_CHAR1&0x80)?1:0);
unsigned long addr = GRAPHICS + (unsigned int)(x1/8) * 64 * 25 + (unsigned int)(y1*8) + (unsigned char)(x1&7);
unsigned int count = (unsigned int)dx;
char is_slope_negative = ((y2 - y1) < 0) ? 1 : 0;