##  (c) Jim 'bob' 1997
##  www.playstation.co.uk/~Sig1LL
##  sigill@geocities.com
##
##  shitty screen wibbler/lava lamp sorta thing.
##  This is really a test prog to see what sort
##  of work loads the r3000 can handle before
##  it starts maxing out.
##  It really proves that the gpu/gte combo
##  are the real workhorses on the psx.
##  I guess I could speed it up a bit by
##  taking LoadImage apart to step up the
##  DMA transfer to vram.
##  If I get some time soon I may move it
##  to 100% asm to cut out the annoying
##  frame loop.  Then I should be able to
##  avoid doing the stack frame.
##  I wonder if I could cut down the trigtab
##  and jam it in the dCache? I could also
##  structure the delay slots a little 
##  (read lot) better too.
##  
##  Let me know what you do with this.
##	All the best  - Jim

.text
.align	2
.globl	DrawFrame
.ent	DrawFrame
DrawFrame:
	.frame	$fp,40,$31		
	subu	$sp,$sp,40
	sw	$fp,32($sp)
	sw	$31,36($sp)
	
	la	$5, 0x1f800010	
	
	addu	$10,$0,1
	
	lw	$4, 0($5)
	
	la	$11,0x80120000
	
	addu	$4,$4,4
	
	addu	$9,$0,0
	
	and	$4,$4,0x3ff
	
	sw	$4, 0($5)
	
	
$outer:
	la 	$14, 0x80092000		#costab
	sll	$24, $9, 2		# y * 4
	addu	$24,$24,$14		# cost[y]
	lw	$24, 0($24)		# sty_b
	
	la 	$14, 0x80090000		#sintab
	sll	$25, $9, 2		# y * 4
	addu	$25,$25,$14		# sint[y]
	lw	$25, 0($25)		# sty_a
	
	addu	$8,$0,0
$iner:
	la 	$14, 0x80090000
	
# calc XX	
	add	$5, $4, $8		# theta = theta +x
	and 	$5, $5, 0x3ff
	sll	$5, $5, 2		# thetax * 4

	add	$14, $14, $5		# sintab[thetax]
	lw 	$14, 0($14)

        sll	$6, $4, 1		# theta << 1
	srl	$12, $8, 1		# x >> 1
	add	$6, $6, $12		# (theta <<1) + (x >> 1)
	
	
	add	$6, $24, $6		# (theta<<1)+(x>>1)+cos[y]
	subu 	$13,$6,$14
	
	srl	$13, $13, 4		# >> 4
	and     $13, $13, 16		# & 16	
	srl	$13, $13, 2		# >> 3
# calc yy	
	
	la 	$6, 0x80092000
	add	$6, $6, $5		# costab[thetax]
	lw 	$6, 0($6)
	
        add    $14, $12, $25		# x >> 1+ sty_a
	add    $14, $14, $6
	
	srl	$14, $14, 4
	and	$14, $14, 16
	srl	$14, $14, 1
	
	la	$12, 0x1f800000
	or	$13,$13,$14

        add    $12, $12, $13	
	lh	$13, 0($12)
	

	sh 	$13, 0($11)
	add	$11,$11,2
	

	addu   $8,$8,1
	ble   $8,255,$iner
	nop
	
	addu   $9,$9,1
	ble   $9,200, $outer
	
	jal	DrawSync
	la	$4, 0
	
	jal	VSync
	jal 	GsSwapDispBuff
	
	
	la 	$4, Page
	lw	$8,0($4)
	not	$5,$8
	sw	$5,0($4)
	
	la 	$4,0x1f800014	
	and	$8,$8,1
	sll	$8,$8,8
	addu	$8,$8,20
	sh	$8,2($4)
	
	la	$5,0x80120000
	jal	LoadImage
	
	
	
	lw	$31,36($sp)
	lw	$fp,32($sp)
	addu	$sp,$sp,40

	j	$31
	nop

.end DrawFrame