Developing NES games (cc65) 05 and palette with C language

Paste the CSDN The format is not adjusted , If you want to see a good format, click below

https://happysoul.github.io/nes/nesdoug/

 

About NES Palette information

 

 

altogether 64 Medium colors available （0-$3F）, But many of them are black .neslib Ask you to use $0F According to black ,$30 Said the white .

Do not use xD Color , In especial $0D ( He will make some TV problems , The oil pipe has video )

 

https://www.youtube.com/watch?v=3fhyX3HdVcg

 

PPU The address of the palette is $3f00-3f0f. Color index #0 （PPU The position in is $3F00 ） Is the general background color . other 3 Palette 0 Sign color and the first palette 0 The color of the sign is the same .

 

Yes 4 A background palette （4 A sprite palette ）,4 Sub palette .

 

U Represents a universal color （ To put it bluntly, next 4 Location U It's all one color , Cut must be the same color ）

U123 U123 U123 U123

The screen shows 13 Medium color .

 

Each map block of the sprite can only be used 3 Color ,0 The numerical value at position No. indicates transparency . Elves use PPU The palette address is $3F10-3F1F, You can use 12 Plant different colors .

 

 

 

up to now , We only used 1 A palette （4 Color ）, So let's use all bg Palette make something .

 

You can use pal_all() Change the entire palette （32 Bytes ）,

Or use pal_bg() change 16 Byte background palette ,

Use pal_spr() change 16 Byte sprite palette .

Just pass one 16 An array of bytes . You can use it. pal_col(index, color)（ Indexes , Color ） change 1 Color , among index yes 0-$1f.

There will be one on the next page pal_col Example （ Spirit collision ）.

 

The palette is located in PPU in , And in PPU Cannot write while rendering , all neslib Palette functions are written to the buffer , The buffer is only in v-blank Period copied to PPU（ stay nmi In the code ）. therefore , You can switch the screen and call these functions at any time .

（ The author means to switch the screen and the above functions casually ,nmi The code will judge v-blank And take it out of the cache and put it in PPU in ）

 

Background attribute table

 

stay PPU in , Each name table （tilemap） At the end of is the attribute table . For maps #0, That is $23c0-$23ff. The only thing they can have “ attribute ” Is palette selection , therefore , You can think of it as a palette table .

 

The name table only has 64 Bytes can be used for palette selection , So we can generate 8×8 grid . Each byte represents BG Of 32×32 block . Each byte is further divided into 2 Bits , Every 2 Bits represent the background 16×16 Block .

 

 

therefore , Each tile does not have its own palette selection . You can only 4（2×2） Block definition palette options .

 

Try to use NES Screen tools and try to change the palette , You can see it immediately .

 

Most games are just 16×16 Design the game in blocks of . I did the same thing .

 

 

Notice how the ground plate and window block are accurately 16×16 Pixels . The column happens to be 32 Pixel width . The curtain area is just 32 Pixel width .

 

There are several options to choose from , It expands our tileset, Because we can reuse the same for different objects by changing its palette tile. Look at the clouds and bushes . They use the same tiles on the top .

 

 

Again ,1 Attribute bytes affect 16×16 block . each 2 position . therefore , The layout of attribute bytes is like this , Bitwise ......

 

In the attribute byte 44332211 position

 

11 22

11 22

33 44

33 44

 

therefore , If the bit 44 Turn into 00, Then the block will use the 0 A palette . If 22 Turn into 01, It will use the next palette and so on .

 

therefore , I am here NES A background is made in the screen tool . The whole picture is gray , Use the palette ＃0, But the code writes the attribute table with padding , Change palette options .

Please note that , I use get_at_addr(0,0,0) To calculate the address in the property sheet . And then use vram_fill() Set attribute bytes .

 

 

In the middle of the game , The property sheet is difficult to modify ...... Displacement and shielding are involved here .

Many games just avoid changing it , Unless as part of the rolling engine . You can design the game as 32×32 block , You only need to change one full byte , Don't worry about displacement .

 

I write a method vram_put() To change 1 Lower attribute bytes , So you can see its size and ability .

 

vram_put(0xe4); // Put in 1 Bytes 1110 0100

 

Now? , If in NES Create background in screen tool , Just save the name table of attribute bytes as compressed rle, And copy it when the game is loaded .

 

https://github.com/nesdoug/06_Color/blob/master/color.c

 

https://github.com/nesdoug/06_Color

 

Part of my library is data element processing , Can handle attribute bytes .