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Example of meta-tile drawing (4 tile x 4 tile) blocks :START SCREEN


bruddog

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Just wanted to give a quick example of how the " TECMO SUPER BOWL" text positioned in 4x4 blocks

 

If we go to 0x05056 in the rom we get the following data:  A5 b6. This is a pointer to the data sequence. Flipping it and andding 0x10 for the ines header offset we get 0xB6B5.

 

Since 0x4000 is loaded in as a $A000 bank. B6B5 points to $56B5

 

At 0x56b5 we have the following sequence

 

20 76                                    ; These first two bytes set which 0x0800 size banks from the CHR section of the rom (0x40010 onwards in 28 team)

                                             ; we will use that contain the tiles we need

02                                         ;  This byte tells us which bank will be used to draw the 4x4 tile sections 

20                                         ;  This byte sets our background pallete index

03, 06                                   ; These two bytes set (# of metatile rows, # length of the metatile sequence) 

09                                         ; this byte sets the starting location for the metatiles (refer to the image below) 

42 43 44 45 46 00 ; these are pointer indexes to draw the metatiles

47 48 49 4A 4B 4C

00 4D 4E 4F 50 AB

 

I made a spreadsheet helper to make things clearer refer to the image below

 

Going through the first line

 

42= draws part of the white S

43= top part of the S and part of the U

44, draws the red TEC and part of the m as well as part of the top of the U and P. 

metatile.png

http://puu.sh/m0Sdp/8d2ff758af.png

metatile.bmp

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  • 5 years later...

Just want to say thank you to bruddog for this specific post. This right here truly is the Rosetta Stone of Tecmo graphics. Once you understand this post, you can customize just about any graphical element. I've now created new opening images, new end zone and 50-yard line graphics, new credits images, and custom scoreboard signage. Not just small tile edits but 100% completely new images from scratch. None of the above would be possible without this specific post. I hope to write some guides myself to help others out and show what I have learned but again, it is all possible once you grasp the way Tecmo graphics are stored, which is right here. 

 

Thanks again man!
 

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I've tried a few patterns, but the general process is something like:

  • screenshot the desired image
  • crop sides to get to exact dimensions - some multiple of 64x128 in this case
  • in GIMP or a more basic photo editor, erase all of the background - any background will make it harder for the color-reduction algorithms to make the face look good
  • in GIMP, experiment with Posterize and Noise filters
  • also in GIMP, adjusting Levels or Contrast/Brightness can really improve a photo 
  • resize (scale) to exact dimensions
  • export as PNG
  • import in GraphicsGale, set Color Depth to 4 colors
  • save as BMP
  • import into NESst
  • save as CHR file
  • import CHR tiles into custom Tecmo ROM

The most trial-and-error is with Levels, Contrast and Brightness, then seeing how that looks after reducing to 4 colors in Gale. Obviously you will lose a ton of detail by reducing the image to 4 colors, but getting the Levels right can help restore as much as possible.

 

I plan to submit a few writeups, however I am still experimenting a little and learning more as I go.

 

 

Edited by ovenmitt
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