From d1a0ac9144c949d81780d3eadceedf78e6b15ac5 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sat, 30 Dec 2017 00:43:39 -0500
Subject: [PATCH] mode7: more starfield work

---
 asm_routines/hlin_clearscreen.s |  2 +-
 gr-sim/starfield_fixed.c        | 10 ++--
 mode7/starfield_demo.s          | 88 +++++++++++++++++++++++++++++++--
 mode7/zp.inc                    |  1 +
 4 files changed, 92 insertions(+), 9 deletions(-)

diff --git a/asm_routines/hlin_clearscreen.s b/asm_routines/hlin_clearscreen.s
index 46dab7b6..1024ca21 100644
--- a/asm_routines/hlin_clearscreen.s
+++ b/asm_routines/hlin_clearscreen.s
@@ -183,7 +183,7 @@ clear_top_a:
 
 	; HLIN Y, V2 AT A
 
-	lda	#40
+	lda	#39
 	sta	V2
 
 	lda	#0
diff --git a/gr-sim/starfield_fixed.c b/gr-sim/starfield_fixed.c
index 8af16522..37c02828 100644
--- a/gr-sim/starfield_fixed.c
+++ b/gr-sim/starfield_fixed.c
@@ -83,13 +83,13 @@ static void random_star(int i) {
 	stars[i].x.i=random_table[random_pointer++];
 	if (random_pointer>255) random_pointer=0;
 
-	stars[i].x.f=random_table[random_pointer++];
-	if (random_pointer>255) random_pointer=0;
+//	stars[i].x.f=random_table[random_pointer++];
+//	if (random_pointer>255) random_pointer=0;
 
 	stars[i].y.i=random_table[random_pointer++];
 	if (random_pointer>255) random_pointer=0;
-	stars[i].y.f=random_table[random_pointer++];
-	if (random_pointer>255) random_pointer=0;
+//	stars[i].y.f=random_table[random_pointer++];
+//	if (random_pointer>255) random_pointer=0;
 
 //	double_to_fixed( (drand48()-0.5)*spreadx,&stars[i].x);
 //	double_to_fixed( (drand48()-0.5)*spready,&stars[i].y);
@@ -97,7 +97,7 @@ static void random_star(int i) {
 	/* 0 to 63 corresponding to  */
 	stars[i].z=random_table[random_pointer++]&0x3f;
 	if (random_pointer>255) random_pointer=0;
-	if (stars[i].z>58) stars[i].z=0;
+//	if (stars[i].z>58) stars[i].z=0;
 
 //	double_to_fixed( ((drand48())*spreadz)+0.1,&stars[i].z);
 //	print_fixed(&stars[i].x);
diff --git a/mode7/starfield_demo.s b/mode7/starfield_demo.s
index e40210a8..be6e0f1f 100644
--- a/mode7/starfield_demo.s
+++ b/mode7/starfield_demo.s
@@ -27,19 +27,49 @@ NUMSTARS	EQU	16
 	;===============
 	lda	#0
 	sta	DRAW_PAGE
+	sta	RANDOM_POINTER
+
+	ldy	#NUMSTARS
+init_stars:
+	jsr	random_star
+	dey
+	bpl	init_stars
+
+	;===========================
+	;===========================
+	; Main Loop
+	;===========================
+	;===========================
 
 starfield_loop:
 
+	;===============
+	; clear screen
+	;===============
+	jsr	clear_top
+
 	;===============
 	; draw stars
 	;===============
 
-draw_stars:
 	ldx	#NUMSTARS
 
+draw_stars:
+	txa
+	tay
+
+	; calculate color
+
+	lda	#$ff
+	sta	COLOR
+
+	; calculate x and y
+
 	lda	#20
 	ldy	#20
 
+	;================================
+	; plot routine
 	;================================
 	; put address in GBASL/GBASH
 	; Xcoord in A, Ycoord in Y
@@ -57,12 +87,33 @@ draw_stars:
 								;===========
 								;
 
+	lda	TEMPY
+	and	#$1
+	bne	plot_odd
+plot_even:
+	lda	COLOR
+	and	#$f0
+	sta	COLOR
+	lda	(GBASL),Y
+	and	#$0f
+	jmp	plot_write
+plot_odd:
+	lda	COLOR
+	and	#$0f
+	sta	COLOR
+	lda	(GBASL),Y
+	and	#$f0
+
+plot_write:
 	ldy	#0
-	lda	#$ff
+	ora	COLOR
 	sta	(GBASL),Y
 
+
+	;==============================
+
 	dex
-	bne	draw_stars
+	bpl	draw_stars
 
 
 starfield_keyboard:
@@ -90,6 +141,37 @@ skipskip:
 	jmp	starfield_loop						; 3
 
 
+; matches scroll_row1 - row3
+star_x	EQU	$8A00
+star_y	EQU	$8B00
+star_z	EQU	$8C00
+
+	;===================
+	; star number in Y
+	; FIXME: increment at end?
+	; X trashed
+random_star:
+	; random x location
+	ldx	RANDOM_POINTER
+	lda	random_table,X
+	inc	RANDOM_POINTER
+	sta	star_x,Y
+
+	; random y location
+	ldx	RANDOM_POINTER
+	lda	random_table,X
+	inc	RANDOM_POINTER
+	sta	star_y,Y
+
+	; random z location
+	ldx	RANDOM_POINTER
+	lda	random_table,X
+	inc	RANDOM_POINTER
+	and	#$3f
+	sta	star_z,Y
+
+	rts
+
 ;===============================================
 ; External modules
 ;===============================================
diff --git a/mode7/zp.inc b/mode7/zp.inc
index 095b624c..0d865cdd 100644
--- a/mode7/zp.inc
+++ b/mode7/zp.inc
@@ -95,6 +95,7 @@ LAST_SPACEY_I	EQU	$88
 LAST_MAP_COLOR	EQU	$89
 DRAW_SKY	EQU	$8A
 COLOR_MASK	EQU	$8B
+RANDOM_POINTER	EQU	$8C
 
 SHIPY           EQU     $E4