Riven SFXE resources - Revision history

TitoDalCanton: killed the legacy first line

2008-04-05T10:09:32Z

killed the legacy first line

TitoDalCanton: other SFXE improvements

2008-04-04T21:38:41Z

other SFXE improvements

TitoDalCanton: better explanation of how the effect takes place

2008-04-04T21:31:45Z

better explanation of how the effect takes place

BahamutZERO: /* The header */

2008-03-27T12:37:10Z

‎The header

Di gama: TOC

2008-02-06T02:21:15Z

TOC

Di gama: import

2008-02-05T01:44:36Z

import

New page

This document talks about Riven resources controlling where to apply the water special effect.

==What is an SFXE resource?==
SFXE data has to do with the water special effect, which works by taking pixels from the rendered card picture and slightly moving them in periodic motion according to precomputed animation frames. Each frame consists of "displacement commands" that take pixel rows from the original picture and copy them at specified positions over a copy of the same picture. Displacement commands in each frame are arranged in a way that already takes into account periodic motion: the rendering code just loops interpreting frame after frame, blindly copying pixel rows over a copy of the original image.

SFXE data is divided in 4 sections: the header, an unknown and apparently unused section, an offset table and a frame section. The offset table points to frames in the frame section. Everything is in big-endian byte order.

==The header==
First of all comes a 52-byte header:
{| class="structure"
|char||magic[2]
|-
|unsigned short||frame_count
|-
|unsigned long||offset_table_position
|-
|unsigned short||left, top, right, bottom
|-
|unsigned short||effect_speed
|-
|unsigned short||u0
|-
|unsigned short||alt_top, alt_left, alt_bottom, alt_right
|-
|unsigned short||u1
|-
|unsigned short||alt_frame_count
|-
|unsigned long||u2
|-
|unsigned long||u3
|-
|unsigned long||u4
|-
|unsigned long||u5
|-
|unsigned long||u6
|}

*''magic'' is the string "SL". Maybe it identifies a known format, but I've found no info;
*''frame_count'' is the number of animation frames;
*''offset_table_position'' seems always 164. Probably it is the position of the offset table relative to the beginning of the resource, which is exactly 52+112=164. Altering this field makes Riven crash.
*''left'', ''top'', ''right'', ''bottom'' define the global rectangle of the effect area within the 608x392 game window. Note that ''right'' and ''bottom'' exceed by 1 pixel (that is, fullscreen SFXE resources have right = 608 and bottom = 392, not 607 and 391);
*''effect_speed'' seems always 15. It controls the speed of the water effect, and seems in units of frames per second;
*''alt_top'', ''alt_left'', ''alt_bottom'', ''alt_right'' is a copy of the previous rectangle. It seems ignored by the engine, changing it doesn't produce effects;
*''u1'' seems always 0;
*''alt_frame_count'' is a copy of frame_count;
*''u2'', ''u3'', ''u4'', ''u5'' seem always 4, 0, 0x19 and 1 respectively;
*''u6'' seems always 0 or 0x10000000;

Altering any of the unknown fields ''u0''...''u6'' produces no apparent change at all, nor makes the engine crash. They look really like a waste of space.

==The unknown section==
This is a 112-byte block of unknown purpose. It seems divided into 8-byte rows, and looks like an encoded mask or a [[Riven tBMP resources|tBMP]] command stream. The values don't change very much between resources and show the same structure. Incredibly enough, altering any of these values doesn't produce observable effects! Well, I've tried only on a few resources, but this behavior is quite disappointing. This data looks like a structure that was discarded in the final version of the engine, but was left in SFXE resources.

==The offset table==
This is just an array of ''frame_count'' unsigned long offsets, relative to the beginning of the resource. Each offset points to a frame in the frame section.

==The frame section==
This section contains ''frame_count'' data blocks, each representing an animation frame. Each block is made of a variable number of commands. Each command is an unsigned short opcode optionally followed by arguments. 3 opcodes have been observed:
*Command 1 has no arguments. It increments ''current_row'' by one pixel; ''current_row'' is a variable that scans the effect area row by row, starting from top. It's used by command 3 to help copying pixel rows. The number of "1" commands inside a frame is equal to the effect area height in pixels, that is, the number of pixel rows affected.
*Command 3 has 4 unsigned short arguments, ''dst_left src_left src_top row_width''. It defines the displacement: take a row of ''row_width'' pixels from the original picture at (''src_left'',''src_top'') and copy it at (''dst_left,''current_row'').
*Command 4 is the last command and ends the frame.

← Older revision		Revision as of 10:09, 5 April 2008
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	{{Riven}}		{{Riven}}
−	~~This document talks about Riven resources controlling where to apply the water special effect.~~

	==What is an SFXE resource?==		==What is an SFXE resource?==

← Older revision		Revision as of 02:21, 6 February 2008
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		+	{{Riven}}
	This document talks about Riven resources controlling where to apply the water special effect.		This document talks about Riven resources controlling where to apply the water special effect.

@@ Line 3: / Line 3: @@
 ==What is an SFXE resource?==
-SFXE data has to do with the water special effect, which works by taking pixels from the rendered card picture and slightly moving them in periodic motion according to precomputed animation frames. Each frame consists of "displacement commands" that take pixel rows from the original picture and copy them at specified positions over the front viewport. Displacement commands in each frame are arranged in a way that already takes into account periodic motion: the rendering code just loops interpreting frame after frame, blindly copying pixel rows from the offscreen, pre-composited card picture to the visible screen.
+SFXE data has to do with the water special effect, which works by taking pixels from the rendered card picture and slightly moving them in periodic motion according to precomputed animation frames. Each frame consists of "displacement commands" that take pixel rows from the original picture and copy them at specified positions over the front viewport. Displacement commands in each frame are arranged in a way that already takes into account periodic motion: the rendering code just loops interpreting frame after frame, blindly copying pixel rows from the offscreen, pre-composited card picture to the visible screen. It is a reasonably simple algorithm whith a low number of pixels copied each second, attaining good performance even in the slow systems targeted by the original engine.
 SFXE data is divided in 4 sections: the header, an unknown and apparently unused section, an offset table and a frame section. The offset table points to frames in the frame section. Everything is in big-endian byte order.
@@ Line 49: / Line 49: @@
 *''u2'', ''u3'', ''u4'', ''u5'' seem always 4, 0, 0x19 and 1 respectively;
 *''u6'' seems always 0 or 0x10000000;
 Altering any of the unknown fields ''u0''...''u6'' produces no apparent change at all, nor makes the engine crash. They look really like a waste of space.
@@ Line 60: / Line 62: @@
 ==The frame section==
 This section contains ''frame_count'' data blocks, each representing an animation frame. Each block is made of a variable number of commands. Each command is an unsigned short opcode optionally followed by arguments. 3 opcodes have been observed:
-*Command 1 has no arguments. It increments ''current_row'' by one pixel; ''current_row'' is a variable that scans the effect area row by row, starting from top. It's used by command 3 to help copying pixel rows. The number of "1" commands inside a frame is equal to the effect area height in pixels, that is, the number of pixel rows affected.
+*Command 1 has no arguments. It increments ''current_row'' by one pixel; ''current_row'' is a variable that scans the effect area row by row, starting from ''top'' (defined in the header). It is used by command 3 to help copying pixel rows. The number of "1" commands inside a frame is equal to the effect area height in pixels, that is, the number of pixel rows affected.
-*Command 3 has 4 unsigned short arguments, ''dst_left src_left src_top row_width''. It defines the displacement: take a row of ''row_width'' pixels from the original picture at (''src_left'',''src_top'') and copy it at (''dst_left,''current_row'') on the viewport.
+*Command 3 has 4 unsigned short arguments, ''dst_left src_left src_top row_width''. It defines the displacement: take a row of ''row_width'' pixels from the original picture at (''src_left'',''src_top'') and copy it at (''dst_left'',''current_row'') on the viewport.
 *Command 4 is the last command and ends the frame.

@@ Line 10: / Line 10: @@
 First of all comes a 52-byte header:
 {| class="structure"
-|char||magic[2]
+|int8_t||magic[2]
 |-
-|unsigned short||frame_count
+|uint16_t||frame_count
 |-
-|unsigned long||offset_table_position
+|uint32_t||offset_table_position
 |-
-|unsigned short||left, top, right, bottom
+| uint16_t ||left, top, right, bottom
 |-
-|unsigned short||effect_speed
+| uint16_t ||effect_speed
 |-
-|unsigned short||u0
+| uint16_t ||u0
 |-
-|unsigned short||alt_top, alt_left, alt_bottom, alt_right
+| uint16_t ||alt_top, alt_left, alt_bottom, alt_right
 |-
-|unsigned short||u1
+| uint16_t ||u1
 |-
-|unsigned short||alt_frame_count
+| uint16_t ||alt_frame_count
 |-
-|unsigned long||u2
+| uint32_t ||u2
 |-
-|unsigned long||u3
+| uint32_t ||u3
 |-
-|unsigned long||u4
+| uint32_t ||u4
 |-
-|unsigned long||u5
+| uint32_t ||u5
 |-
-|unsigned long||u6
+| uint32_t ||u6
 |}