I got the first few steps done last night. When I am finished I will post a word version with pictures.
Read the basics here.
http://www.chronocompendium.com/Forums/index.php?topic=2872.0Sprite Assembly in Chrono Trigger
By Vargose
Needed Tools
1. A Hex Editor of your choice. I used Translhextion.
2. TileMolester
3. The sprite you intend to import.
4. Irfanview
5. Paint and/or Microsoft Photo Editor
6. The Chrono Trigger Offsets Guide
7. An Unheadered rom of Chrono Trigger
8. Lots of Patients
History
Vehek researched and discovered the inner workings of sprite assembly. I learned what I know from his post on the Chrono Compendium Forums. This is for sprites of size type 0 (Chrono Tweaker), which include the playable characters.
Definitions
• Tiles – 8 pixel by 8 pixel squares.
• Tile Group – a group of four tiles used in sprite assembly
• Frames – a single sprite, made up of 4 four tile groups in the case of size 0 sprites.
• Animations – a sequence of frames.
GOAL: Successfully import a custom sprite into Chrono Trigger
STEP 1: Prepare the custom sprite for importing
• You have 4 tile groups to work with. That’s mean you will have to size the sprite to fit into any configuration of four 16 by 16 pixel squares.
• For this tutorial I have chosen to use a sprite from Final Fantasy Tactics, specifically Cloud Strife. I also made a 16 by 16 sprite of the top of his buster sword for demonstration purposes.
• The original sprite itself was 37 pixels tall. The CT playable characters are 32 pixels tall. 32 is 86% of 37, so I shrank the sprite by 86% using the stretch/skew command in Paint.
• CT playable characters have 12 colors one of which is transparent. Make sure the background color is not used in the sprite itself, because it will be replaced by the transparent color later (green screen trick). Open the sprite in Irfanview and decrease the color depth to 12 using the decrease color depth tool in the image menu.
STEP 2: Changing the color Palette
• Open the sprite in Irfanview. Click edit palette in the palette submenu of the image menu. Click on each color (except your green screen transparency color) and record the RGB values (should be 11 colors). Divide each number by 8 to get the corresponding Chrono Trigger RGB value, or in SNESPal enter each RGB value into the search boxes with the auto-convert check box checked, and then uncheck it to get the corresponding values.
• Open the rom in SNESPal and edit the palette of the sprite you intend to replace. For this tutorial we will replace Crono. The offset to the character palettes, according to the Chrono Trigger offsets guide, is 240000. The first palette is Crono’s. Each palette contains 11 colors that last of which is transparent. Input each of the RGB values and save.
• Now Open the rom in Zsnes, and when Crono appears on screen with his new palette make a save state.
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