Windows: Difference between revisions
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* [[Backgrounds|Background]] layers (BG1, BG2, BG3, BG4) | * [[Backgrounds|Background]] layers (BG1, BG2, BG3, BG4) | ||
* The [[Sprites|Sprite]] layer (OBJ) | * The [[Sprites|Sprite]] layer (OBJ) | ||
* [[ | * The main screen | ||
* The sub screen ([[color math]]) | |||
== Registers == | == Registers == | ||
See: [[PPU registers#Windows|PPU registers: Windows]] | |||
{| class="wikitable" | {| class="wikitable" | ||
| Line 29: | Line 32: | ||
| style="text-align: right" | <tt style="white-space: nowrap">LlKk JjIi</tt> | | style="text-align: right" | <tt style="white-space: nowrap">LlKk JjIi</tt> | ||
| W8 | | W8 | ||
| Enable (IJKL) and Invert (ijkl) windows for OBJ (IJ) and color | | Enable (IJKL) and Invert (ijkl) windows for OBJ (IJ) and color (KL). | ||
|- | |- | ||
! [[PPU registers#WH0|WH0]] | ! [[PPU registers#WH0|WH0]] | ||
| Line 65: | Line 68: | ||
| style="text-align: right" | <tt style="white-space: nowrap">.... CCOO</tt> | | style="text-align: right" | <tt style="white-space: nowrap">.... CCOO</tt> | ||
| W8 | | W8 | ||
| Window mask logic for OBJ (O) and color | | Window mask logic for OBJ (O) and color (C). | ||
|- | |- | ||
! [[PPU registers#TMW|TMW]] | ! [[PPU registers#TMW|TMW]] | ||
| Line 83: | Line 86: | ||
| style="text-align: right" | <tt style="white-space: nowrap">MMSS ..AD</tt> | | style="text-align: right" | <tt style="white-space: nowrap">MMSS ..AD</tt> | ||
| W8 | | W8 | ||
| main/sub screen color | | main/sub screen color window black/transparent regions (MS), fixed/subscreen (A), direct color (D). | ||
|} | |} | ||
== Window == | == Window == | ||
The SNES has two window devices. | The SNES has two window devices which can be used to selectively cut holes out of parts of the picture. | ||
Each window has a left and right pixel position ([[PPU registers#WH0|WH0]]/[[PPU registers#WH1|WH1]]/[[PPU registers#WH2|WH2]]/[[PPU registers#WH3|WH3]]) where the window should hide the affected layers. The window effect (1 output) is at left <= X <= right. If left > right then the window is | Each window has a left and right pixel position ([[PPU registers#WH0|WH0]]/[[PPU registers#WH1|WH1]]/[[PPU registers#WH2|WH2]]/[[PPU registers#WH3|WH3]]) where the window should hide the affected layers. The window effect (1 output) is at left <= X <= right. If left > right then the window effect is nowhere (all 0 output). [[HDMA]] can be used to [[Drawing window shapes|create shapes]] by adjusting the left/right position for each scanline. | ||
Each window can be separately enabled for the various layers, and also inverted ([[PPU registers#W12SEL|W12SEL]]/[[PPU registers#W34SEL|W34SEL]]). If the window is inverted, the left/right position instead defines where the window should ''not'' hide the affected layers (if left > right, the window effect is everywhere, all 1 output). If the window is disabled then invert has no effect (all 0 output). | |||
Additionally if two windows are enabled for the same layer, boolean logic can be applied between them ([[PPU registers#WBGLOG|WBGLOG]]/[[PPU registers#WOBJSEL|WOBJSEL]]). An individual window is 0 when showing the layer, and 1 when hiding it. This logic will combine the effect of both windows in the chosen way. | Additionally if two windows are enabled for the same layer, boolean logic can be applied between them ([[PPU registers#WBGLOG|WBGLOG]]/[[PPU registers#WOBJSEL|WOBJSEL]]). An individual window is 0 when showing the layer, and 1 when hiding it. This logic will combine the effect of both windows in the chosen way. | ||
The windows can be selectively applied to the main screen and sub screen layers ([[PPU registers#TMW|TMW]]/[[PPU registers#TSW|TSW]]). | |||
Finally, the color window can be used to black areas of the main screen, or create a transparent region on the sub screen to mask [[color math]] ([[PPU registers#CGWSEL|CGWSEL]]). | |||
== Window Mask Logic == | |||
If both windows are enabled on the same layer, they will be combined using either OR, AND, XOR or XNOR boolean logic as set by the [[PPU_registers#Window_mask_logic|Window mask logic registers]] (<tt>WBGLOG</tt>/<tt>WOBJLOG</tt>). | |||
When the window mask logic bits are combined with the ''invert window'' flags they form 16 different configurations, 10 of which are unique. | |||
[[File:Window_mask_logic_table.png|frame|center|The 4 window mask logic settings combined with the 2 invert window flags]] | |||
== See Also == | == See Also == | ||
Latest revision as of 09:00, 23 October 2023
Windows are used to hide layers from regions of the screen. On a per-scanline basis, they can be used to cut out areas of:
- Background layers (BG1, BG2, BG3, BG4)
- The Sprite layer (OBJ)
- The main screen
- The sub screen (color math)
Registers
| Name | Address | Bits | Type | Notes |
|---|---|---|---|---|
| W12SEL | $2123 | DdCc BbAa | W8 | Enable (ABCD) and Invert (abcd) windows for BG1 (AB) and BG2 (CD). |
| W34SEL | $2124 | DdCc BbAa | W8 | Enable (EFGH) and Invert (efgh) windows for BG3 (EF) and BG2 (GH). |
| WOBJSEL | $2125 | LlKk JjIi | W8 | Enable (IJKL) and Invert (ijkl) windows for OBJ (IJ) and color (KL). |
| WH0 | $2126 | LLLL LLLL | W8 | Window 1 left position. |
| WH1 | $2127 | RRRR RRRR | W8 | Window 1 right position. |
| WH2 | $2128 | LLLL LLLL | W8 | Window 2 left position. |
| WH3 | $2129 | RRRR RRRR | W8 | Window 2 right position. |
| WBGLOG | $212A | 4433 2211 | W8 | Window mask logic for BG layers (00=OR, 01=AND, 10=XOR, 11=XNOR). |
| WOBJLOG | $212B | .... CCOO | W8 | Window mask logic for OBJ (O) and color (C). |
| TMW | $212E | ...O 4321 | W8 | Main screen layer window enable. |
| TSW | $212F | ...O 4321 | W8 | Sub screen layer window enable. |
| CGWSEL | $2130 | MMSS ..AD | W8 | main/sub screen color window black/transparent regions (MS), fixed/subscreen (A), direct color (D). |
Window
The SNES has two window devices which can be used to selectively cut holes out of parts of the picture.
Each window has a left and right pixel position (WH0/WH1/WH2/WH3) where the window should hide the affected layers. The window effect (1 output) is at left <= X <= right. If left > right then the window effect is nowhere (all 0 output). HDMA can be used to create shapes by adjusting the left/right position for each scanline.
Each window can be separately enabled for the various layers, and also inverted (W12SEL/W34SEL). If the window is inverted, the left/right position instead defines where the window should not hide the affected layers (if left > right, the window effect is everywhere, all 1 output). If the window is disabled then invert has no effect (all 0 output).
Additionally if two windows are enabled for the same layer, boolean logic can be applied between them (WBGLOG/WOBJSEL). An individual window is 0 when showing the layer, and 1 when hiding it. This logic will combine the effect of both windows in the chosen way.
The windows can be selectively applied to the main screen and sub screen layers (TMW/TSW).
Finally, the color window can be used to black areas of the main screen, or create a transparent region on the sub screen to mask color math (CGWSEL).
Window Mask Logic
If both windows are enabled on the same layer, they will be combined using either OR, AND, XOR or XNOR boolean logic as set by the Window mask logic registers (WBGLOG/WOBJLOG).
When the window mask logic bits are combined with the invert window flags they form 16 different configurations, 10 of which are unique.
