Fading colors: Difference between revisions
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== Palette fades == | == Palette fades == | ||
Palettes can be faded to white or black by respectively incrementing or decrementing each color component of each color individually. | [[Palettes]] can be faded to white or black by respectively incrementing or decrementing each color component of each color individually. | ||
Of course, care has to be taken so that each value stops at $1F or 0. | Of course, care has to be taken so that each value stops at $1F or 0. | ||
Fading to a specific color can also be done this way, by comparing each actual components to the target ones and incrementing/decrementing them accordingly. | Fading to a specific color can also be done this way, by comparing each actual components to the target ones and incrementing/decrementing them accordingly (see example code). | ||
== Simulated fades == | == Simulated fades == | ||
[[File:Sengoku3fade.png|frame| | [[File:Sengoku3fade.png|frame|Fix fade to white in [[Sengoku 3]]'s intro]] | ||
[[File:0003.png|frame|Fix wipe in Metal Slug 3]] | |||
Since it has the highest priority on the screen, the [[fix layer]] can be used to fade the underlaying display by using pre-dithered tiles. | Since it has the highest priority on the screen, the [[fix layer]] can be used to fade the underlaying display by using pre-dithered tiles. | ||
| Line 14: | Line 16: | ||
This is also used in [[Metal Slug 3]] as transitions in between areas of certain levels (uses a sprite layer instead of the fix ?). | This is also used in [[Metal Slug 3]] as transitions in between areas of certain levels (uses a sprite layer instead of the fix ?). | ||
== Color handling code == | |||
If not using pre-calculated palette tables for fades, each color component of each color needs to be modified. | |||
<pre> | |||
NG2RGB: | |||
;D3:NG Palette word -> D2:RGB555 word (ignores common bit) | |||
clr.l d2 | |||
;Red | |||
move.w d3,d0 ;DrvbRRRRVVVVBBBB | |||
andi.w #$0F00,d0 ;____RRRR________ | |||
lsl.w #3,d0 ;_RRRR___________ | |||
or.w d0,d2 | |||
move.w d3,d0 | |||
andi.w #$4000,d0 ;_r______________ | |||
lsr.w #4,d0 ;_____r__________ | |||
or.w d0,d2 ;_RRRRr__________ | |||
;Green | |||
move.w d3,d0 ;DrvbRRRRVVVVBBBB | |||
andi.w #$00F0,d0 ;________VVVV____ | |||
lsl.w #2,d0 ;______VVVV______ | |||
or.w d0,d2 __RRRRrVVVV______ | |||
move.w d3,d0 | |||
andi.w #$2000,d0 ;__v_____________ | |||
lsr.w #8,d0 ;__________v_____ | |||
or.w d0,d2 ;_RRRRrVVVVv_____ | |||
;Blue | |||
move.w d3,d0 ;DrvbRRRRVVVVBBBB | |||
andi.w #$000F,d0 ;____________BBBB | |||
lsl.b #1,d0 ;___________BBBB_ | |||
or.w d0,d2 ;_RRRRrVVVVvBBBB_ | |||
move.w d3,d0 | |||
andi.w #$1000,d0 ;___b____________ | |||
rol.w #4,d0 ;_______________b | |||
or.w d0,d2 ;_RRRRrVVVVvBBBBb | |||
rts | |||
</pre> | |||
<pre> | |||
RGB2NG: | |||
;D4:RGB555 word -> D2:NG Palette word (ignores common bit) | |||
clr.l d2 | |||
;Red | |||
move.w d4,d0 ;_RRRRrVVVVvBBBBb | |||
andi.w #$7800,d0 ;_RRRR___________ | |||
lsr.w #3,d0 ;____RRRR________ | |||
or.w d0,d2 ;____RRRR________ | |||
move.w d4,d0 | |||
andi.w #$0400,d0 ;_____r__________ | |||
lsl.w #4,d0 ;_r______________ | |||
or.w d0,d2 ;_r__RRRR________ | |||
;Green | |||
move.w d4,d0 | |||
move.w d4,d1 ;_RRRRrVVVVvBBBBb | |||
andi.w #$03C0,d0 ;______VVVV______ | |||
lsr.w #2,d0 ;________VVVV____ | |||
or.w d0,d2 ;_r__RRRRVVVV____ | |||
move.w d4,d0 | |||
andi.w #$0020,d0 ;__________v_____ | |||
lsl.w #8,d0 ;__v_____________ | |||
or.w d0,d2 ;_rv_RRRRVVVV____ | |||
;Blue | |||
move.w d4,d0 | |||
move.w d4,d1 ;_RRRRrVVVVvBBBBb | |||
andi.w #$001E,d0 ;___________BBBB_ | |||
lsr.b #1,d0 ;____________BBBB | |||
or.w d0,d2 ;_rv_RRRRVVVVBBBB | |||
move.w d4,d0 | |||
andi.w #$0001,d0 ;_______________b | |||
ror.w #4,d0 ;___b____________ | |||
or.w d0,d2 ;_rvbRRRRVVVVBBBB | |||
rts | |||
</pre> | |||
RGB components can then be compared with a target palette in RAM and adjusted until they match, for example: | |||
<pre> | |||
;Compares 555 RGB red in D0 with D1 | |||
andi.w #$7C00,d0 | |||
andi.w #$7C00,d1 | |||
cmp.w d1,d0 | |||
blo .lower | |||
bhi .higher | |||
bra .same | |||
.lower: | |||
addi.w #$0400,d4 | |||
bra .same | |||
.higher: | |||
subi.w #$0400,d4 | |||
.same: | |||
</pre> | |||
[[Category:Code]] | [[Category:Code]] | ||
Revision as of 02:46, 2 August 2011
Palette fades
Palettes can be faded to white or black by respectively incrementing or decrementing each color component of each color individually. Of course, care has to be taken so that each value stops at $1F or 0.
Fading to a specific color can also be done this way, by comparing each actual components to the target ones and incrementing/decrementing them accordingly (see example code).
Simulated fades
Since it has the highest priority on the screen, the fix layer can be used to fade the underlaying display by using pre-dithered tiles. This can only be used if the fix doesn't have to show important information.
This is also used in Metal Slug 3 as transitions in between areas of certain levels (uses a sprite layer instead of the fix ?).
Color handling code
If not using pre-calculated palette tables for fades, each color component of each color needs to be modified.
NG2RGB:
;D3:NG Palette word -> D2:RGB555 word (ignores common bit)
clr.l d2
;Red
move.w d3,d0 ;DrvbRRRRVVVVBBBB
andi.w #$0F00,d0 ;____RRRR________
lsl.w #3,d0 ;_RRRR___________
or.w d0,d2
move.w d3,d0
andi.w #$4000,d0 ;_r______________
lsr.w #4,d0 ;_____r__________
or.w d0,d2 ;_RRRRr__________
;Green
move.w d3,d0 ;DrvbRRRRVVVVBBBB
andi.w #$00F0,d0 ;________VVVV____
lsl.w #2,d0 ;______VVVV______
or.w d0,d2 __RRRRrVVVV______
move.w d3,d0
andi.w #$2000,d0 ;__v_____________
lsr.w #8,d0 ;__________v_____
or.w d0,d2 ;_RRRRrVVVVv_____
;Blue
move.w d3,d0 ;DrvbRRRRVVVVBBBB
andi.w #$000F,d0 ;____________BBBB
lsl.b #1,d0 ;___________BBBB_
or.w d0,d2 ;_RRRRrVVVVvBBBB_
move.w d3,d0
andi.w #$1000,d0 ;___b____________
rol.w #4,d0 ;_______________b
or.w d0,d2 ;_RRRRrVVVVvBBBBb
rts
RGB2NG:
;D4:RGB555 word -> D2:NG Palette word (ignores common bit)
clr.l d2
;Red
move.w d4,d0 ;_RRRRrVVVVvBBBBb
andi.w #$7800,d0 ;_RRRR___________
lsr.w #3,d0 ;____RRRR________
or.w d0,d2 ;____RRRR________
move.w d4,d0
andi.w #$0400,d0 ;_____r__________
lsl.w #4,d0 ;_r______________
or.w d0,d2 ;_r__RRRR________
;Green
move.w d4,d0
move.w d4,d1 ;_RRRRrVVVVvBBBBb
andi.w #$03C0,d0 ;______VVVV______
lsr.w #2,d0 ;________VVVV____
or.w d0,d2 ;_r__RRRRVVVV____
move.w d4,d0
andi.w #$0020,d0 ;__________v_____
lsl.w #8,d0 ;__v_____________
or.w d0,d2 ;_rv_RRRRVVVV____
;Blue
move.w d4,d0
move.w d4,d1 ;_RRRRrVVVVvBBBBb
andi.w #$001E,d0 ;___________BBBB_
lsr.b #1,d0 ;____________BBBB
or.w d0,d2 ;_rv_RRRRVVVVBBBB
move.w d4,d0
andi.w #$0001,d0 ;_______________b
ror.w #4,d0 ;___b____________
or.w d0,d2 ;_rvbRRRRVVVVBBBB
rts
RGB components can then be compared with a target palette in RAM and adjusted until they match, for example:
;Compares 555 RGB red in D0 with D1
andi.w #$7C00,d0
andi.w #$7C00,d1
cmp.w d1,d0
blo .lower
bhi .higher
bra .same
.lower:
addi.w #$0400,d4
bra .same
.higher:
subi.w #$0400,d4
.same: