== Bytebattles ==

Bytebattles are a form of live coding, similar to Shader Showdowns, where two contestants compete in writing a visual effect in 25 minutes. The coding environment is the [[Fantasy Consoles|TIC-80 fantasy console]]. However, unlike Shader Showdowns, there is an additional limit: the final code should be 256 characters or less. This requires the contestants to use efficient code (e.g. single letter variables) and to minimize the code (e.g. remove the whitespace), all within the time limit. Unlike in normal TIC-80 sizecoding, there is no compression, so every character counts.

== General notation in this article ==

{|
! Symbol || Meaning
|-
| <code>i</code> || Pixel index
|-
| <code>s</code> || Alias for math.sin
|-
| <code>x</code> || Pixel x-coordinate
|-
| <code>y</code> || Pixel y-coordinate
|}

== Basic optimizations ==

* Functions, that are called three or more times should be aliased. For example, <code>e=elli</code> with <code>e()e()e()</code> is 3 characters shorter than <code>elli()elli()elli()</code>. Functions with 5-character-long names may already benefit from aliasing with two calls: <code>r=rectb</code> with <code>r()r()</code> is 1 character shorter than <code>rectb()rectb()</code>.
* <code>t=0</code> with <code>t=t+.1</code> is 3 characters shorter than <code>t=time()/399</code>.
* <code>for i=0,32639 do x=i%240y=i/240 end</code> is 2-3 characters shorter than <code>for y=0,135 do for x=0,239 do end end</code>.
* <code>(x*x+y*y)^.5</code> is 6 characters shorter than <code>math.sqrt(x*x+y*y)</code>.
* <code>s(w-11)</code> and <code>s(w+8)</code> both approximate <code>math.cos(w)</code>, so only <code>math.sin</code> needs to be aliased. <code>s(w-11)</code> is far more accurate, with the cost of one more character.

== One-lining ==

Most whitespace can be removed from LUA code. For example: <code>x=0y=0</code> is valid. All new lines can be removed or replaced with space, making the whole code a single line:

<syntaxhighlight lang="lua">
function TIC()for i=0,32639 do poke4(i,i)end end
</syntaxhighlight>

'''Warning: Letters <code>a-f</code> and <code>A-F</code> after a number cause problems.''' <code>a=0b=0</code> is not valid code. It is advisable to only used one letter variables in the ranges <code>g-z</code> and <code>G-Z</code> from the start; this will make eventual one-lining easier.

== Load-function ==

Function <code>load</code> takes a string of code and returns a function with no named arguments, with the code as its body. It's particularly useful for shortening the TIC function after one-lining:

<syntaxhighlight lang="lua">
TIC=load'for i=0,32639 do poke4(i,i)end'
</syntaxhighlight>

As a rule of thumb, one-lining and using the load trick can bring a ~ 275 character code down to 256.

<code>load</code> can be even used to minimize a function with parameters: <code>...</code> returns the parameters. For example, the following example saves 3 bytes:

<syntaxhighlight lang="lua">
SCN=load'r=...poke(16320,r)'
</syntaxhighlight>

Multiple parameters can be fetched with <code>x,y=...</code>.

'''Warning: The backslash causes problems when using the load trick.''' In particular, if you have a string with escaped characters in the original code e.g. <code>print("foo\nbar")</code>, then this needs to be double-escaped: <code>load'print("foo\\nbar")'</code>

== Dithering ==

If you have a floating point color value, TIC-80 <code>pix</code> and <code>poke4</code> functions round it (toward zero). To add dithering, add a small value, between 0 and 1, to the color. The best technique depends whether you have <code>x</code> and <code>y</code> available or only <code>i</code> and how many bytes you can spare:

{|
! Expression || Length || Result || Notes
|-
| || || [[File:No dithering.png]] || No dithering
|-
| <code>s(i)*99%1</code> || 9 || [[File:Random dithering.png]] || "random" dithering, use *9 if desperate.
|-
| <code>i*481/960%1</code> || 11 || [[File:Chess dithering.png]] || chess horse, <code>(x/2+y/4)%1</code> if you have x&y
|-
| <code>(x*2-y%2)%4/4</code> || 13 || [[File:Block dithering.png]] || 2x2 block dithering
|-
| <code>(i*2-i//80%2)%4/4</code> || 17 || [[File:Block dithering from i.png]] || 2x2 block dithering (almost), from i only
|}

A quick example demonstrating the 2x2 block dithering:

<syntaxhighlight lang="lua">
function TIC()
cls()
for i=0,2399 do
x=i%240
y=i//240
poke4(i,x/30+(x*2-y%2)%4/4)
end
end
</syntaxhighlight>

== Palettes ==

The following palettes assume that <code>j</code> goes from 0 to 47. Usually there's no need to make a new loop for this: just reuse another loop with <code>j=i%48</code>.

{|
! Expression || Length || Result || Notes
|-
| <code>poke(16320+j,j*5)</code> || 17 || [[File:Gray palette.png]] ||
|-
| <code>poke(16320+j,j%3*j*5)</code> || 21 || [[File:Blue-green-cyan palette.png]] || Good for objects & background
|-
| <code>poke(16320+j,j%3*j/.4)</code> || 22 || [[File:Blue palette.png]] || Use <code>(j+1)%3</code>, <code>(j+2)%3</code> or <code>2*j%3</code> for different colors
|-
| <code>poke(16320+j,s(j)^2*255)</code> || 24 || [[File:Rainbow palette.png]] || Change the phase of the palette with s(j+p)
|-
| <code>poke(16320+j,s(j)^2*j*6)</code> || 24 || [[File:Rainbow faded palette.png]] || Change the phase of the palette with s(j+p)
|-
| <code>poke(16320+j,s(j/15)*255)</code> || 25 || [[File:Blue-brown palette.png]] || <code>s(j/15)^2</code> is less bright
|-
| <code>poke(16320+j,s(j-j%-3)^2*255)</code> || 29 || [[File:Green-beige palette.png]] || <code>j%3*2</code> for a more blue/beige variant, <code>-j%3*4</code> for beige/blue variant
|-
| <code>poke(16320+j,255/(1+2^(4+j%3-j/5)))</code> || 35 || [[File:Bright beige palette.png]] || <code>2*j%3</code> for a pink variant
|-
| <code>poke(16320+j,255/(1+2^(5-j%3-j/5)))</code> || 35 || [[File:Bright blue palette.png]] || <code>2*j%3</code> for a green variant
|-
| <code>poke(16320+j,s(j/15+s(j%3*3))^2*255)</code>|| 37 || [[File:Green-purple palette.png]] || Cyclic, based on [https://iquilezles.org/www/articles/palettes/palettes.htm]
|}

The last one is an entire family of palettes. You can replace <code>s(j%3*3)</code> with any function that depends on <code>j%3</code>; this ensures the palette remains cyclic. Some ideas for tweaking the palettes:
* Invert the colors by adding a <code>-1-</code> in the expression
* Flip the blue/red channels & have the entire palette running backwards by using <code>poke(16367-j,...)</code>
* Abuse the default Sweetie 16 palette, by only setting some of the RGB channels, while keeping others as they are. For example, setting all the blue channels to zero: <code>poke(16322+j*3,0)</code>. Here <code>j</code> is between 0 and 15.

Code for testing palettes:

<syntaxhighlight lang="lua">
function TIC()
cls()
for j=0,47 do poke(16320+j,s(j/15)*255)end
for c=0,15 do rect(c*5,0,5,5,c)end
end
s=math.sin
</syntaxhighlight>

== Motion blur ==

In TIC-80 API, the <code>pix</code> and <code>poke4</code> functions round numbers towards zero. This can be abused for a motion blur: <code>poke4(i,peek4(i)-.9)</code> maps colors 1 to 15 into one lower value, but value 0 stays at it is. Like so:

<syntaxhighlight lang="lua">
function TIC()
t=time()/9
circ(t%240,t%136,9,15)
for i=0,32639 do poke4(i,peek4(i)-.9)end
end
</syntaxhighlight>

== Updating only some pixels ==

Pixel-based effects, especially raycasting and raymarching, can become excessively slow. A simple trick to update only ~ half of the pixels, giving a dithered/motion blur look and making the update smoother:

<syntaxhighlight lang="lua">
function TIC()
t=time()/499
for i=t%2,32639,1.9 do poke4(i,i/4e3+t)end
end
</syntaxhighlight>

== Examples of effects ==

The effects have not been crunched to keep them readable.

=== Plasma ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/499
for i=0,32639 do
x=i%240
y=i/240
v=s(x/50+t)+s(y/22+t)+s(x/32)
poke4(i,v*2%8)
end
end
s=math.sin
</syntaxhighlight>

=== Rotozoomer ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/999
a=s(t-11)
b=s(t)
for i=0,32639 do
x=i%240-120
y=i/240-68
u=a*x-b*y
v=b*x+a*y
poke4(i,(u//1~v//1)//16)
end
end
s=math.sin
</syntaxhighlight>

=== Tunnel ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/199
for i=0,32639 do
x=i%240-s(t/7)*99-120
y=i/240-s(t/9)*49-68
u=math.atan2(y,x)*6/6.29
v=99/(x*x+y*y)^.5+t
poke4(i,u//1~v//1)
end
end
s=math.sin
</syntaxhighlight>

=== Raymarcher ===

The map is a bunch of repeated spheres here.

<syntaxhighlight lang="lua">
function TIC()
for i=0,32639 do
-- ray (u,v,w), not normalized!
u=i%240/120-1
v=i/32639-.5
w=1
-- camera origo (x,y,z)
x=3
y=0
z=time()/999 -- camera moves with time
j=0
repeat
X=x%6-3 -- domain repetition
Y=y%6-3
Z=z%6-3
-- ray not normalized=>reduce scale
m=(X*X+Y*Y+Z*Z)^.5/2-1
x=x+m*u
y=y+m*v
z=z+m*w
j=j+1
until j>15 or m<.1
poke4(i,j)
end
end
</syntaxhighlight>

== Additional Resources ==

* Code from past bytebattles https://livecode.demozoo.org/

Byte Battle

2022-02-19T14:37:44Z

Pestis: /* Load-function */

== Bytebattles ==

Bytebattles are a form of live coding, similar to Shader Showdowns, where two contestants compete in writing a visual effect in 25 minutes. The coding environment is the [[Fantasy Consoles|TIC-80 fantasy console]]. However, unlike Shader Showdowns, there is an additional limit: the final code should be 256 characters or less. This requires the contestants to use efficient code (e.g. single letter variables) and to minimize the code (e.g. remove the whitespace), all within the time limit. Unlike in normal TIC-80 sizecoding, there is no compression, so every character counts.

== General notation in this article ==

{|
! Symbol || Meaning
|-
| <code>i</code> || Pixel index
|-
| <code>s</code> || Alias for math.sin
|-
| <code>x</code> || Pixel x-coordinate
|-
| <code>y</code> || Pixel y-coordinate
|}

== Basic optimizations ==

* Functions, that are called three or more times should be aliased. For example, <code>e=elli</code> with <code>e()e()e()</code> is 3 characters shorter than <code>elli()elli()elli()</code>. Functions with 5-character-long names may already benefit from aliasing with two calls: <code>r=rectb</code> with <code>r()r()</code> is 1 character shorter than <code>rectb()rectb()</code>.
* <code>t=0</code> with <code>t=t+.1</code> is 3 characters shorter than <code>t=time()/399</code>.
* <code>for i=0,32639 do x=i%240y=i/240 end</code> is 2-3 characters shorter than <code>for y=0,135 do for x=0,239 do end end</code>.
* <code>(x*x+y*y)^.5</code> is 6 characters shorter than <code>math.sqrt(x*x+y*y)</code>.
* <code>s(w-11)</code> and <code>s(w+8)</code> both approximate <code>math.cos(w)</code>, so only <code>math.sin</code> needs to be aliased. <code>s(w-11)</code> is far more accurate, with the cost of one more character.

== One-lining ==

Most whitespace can be removed from LUA code. For example: <code>x=0y=0</code> is valid. All new lines can be removed or replaced with space, making the whole code a single line:

<syntaxhighlight lang="lua">
function TIC()for i=0,32639 do poke4(i,i)end end
</syntaxhighlight>

'''Warning: Letters <code>a-f</code> and <code>A-F</code> after a number cause problems.''' <code>a=0b=0</code> is not valid code. It is advisable to only used one letter variables in the ranges <code>g-z</code> and <code>G-Z</code> from the start; this will make eventual one-lining easier.

== Load-function ==

Function <code>load</code> takes a string of code and returns a function with no named arguments, with the code as its body. It's particularly useful for shortening the TIC function after one-lining:

<syntaxhighlight lang="lua">
TIC=load'for i=0,32639 do poke4(i,i)end'
</syntaxhighlight>

As a rule of thumb, one-lining and using the load trick can bring a ~ 275 character code down to 256.

<code>load</code> can be even used to minimize a function with parameters: <code>...</code> returns the parameters. For example, the following example saves 3 bytes:

<syntaxhighlight lang="lua">
SCN=load'r=...poke(16320,r)'
</syntaxhighlight>

Multiple parameters can be fetched with <code>x,y=...</code>.

'''Warning: The backslash causes problems when using the load trick.''' In particular, if you have a string with escaped characters in the original code e.g. <code>print("foo\nbar")</code>, then this needs to be double-escaped: <code>load'print("foo\\nbar")'</code>

== Dithering ==

If you have a floating point color value, TIC-80 <code>pix</code> and <code>poke4</code> functions round it (toward zero). To add dithering, add a small value, between 0 and 1, to the color. The best technique depends whether you have <code>x</code> and <code>y</code> available or only <code>i</code> and how many bytes you can spare:

{|
! Expression || Length || Result || Notes
|-
| || || [[File:No dithering.png]] || No dithering
|-
| <code>s(i)*99%1</code> || 9 || [[File:Random dithering.png]] || "random" dithering, use *9 if desperate
|-
| <code>i*481/960%1</code> || 11 || [[File:Chess dithering.png]] || chess horse, <code>(x/2+y/4)%1</code> if you have x&y
|-
| <code>(x*2-y%2)%4/4</code> || 13 || [[File:Block dithering.png]] || 2x2 block dithering
|-
| <code>(i*2-i//80%2)%4/4</code> || 17 || [[File:Block dithering from i.png]] || 2x2 block dithering (almost), from i only
|}

A quick example demonstrating the 2x2 block dithering:

<syntaxhighlight lang="lua">
function TIC()
cls()
for i=0,2399 do
x=i%240
y=i//240
poke4(i,x/30+(x*2-y%2)%4/4)
end
end
</syntaxhighlight>

== Palettes ==

The following palettes assume that <code>j</code> goes from 0 to 47. Usually there's no need to make a new loop for this: just reuse another loop with <code>j=i%48</code>.

{|
! Expression || Length || Result || Notes
|-
| <code>poke(16320+j,j*5)</code> || 17 || [[File:Gray palette.png]] ||
|-
| <code>poke(16320+j,j%3*j*5)</code> || 21 || [[File:Blue-green-cyan palette.png]] || Good for objects & background
|-
| <code>poke(16320+j,j%3*j/.4)</code> || 22 || [[File:Blue palette.png]] || Use <code>(j+1)%3</code>, <code>(j+2)%3</code> or <code>2*j%3</code> for different colors
|-
| <code>poke(16320+j,s(j)^2*255)</code> || 24 || [[File:Rainbow palette.png]] || Change the phase of the palette with s(j+p)
|-
| <code>poke(16320+j,s(j)^2*j*6)</code> || 24 || [[File:Rainbow faded palette.png]] || Change the phase of the palette with s(j+p)
|-
| <code>poke(16320+j,s(j/15)*255)</code> || 25 || [[File:Blue-brown palette.png]] || <code>s(j/15)^2</code> is less bright
|-
| <code>poke(16320+j,s(j-j%-3)^2*255)</code> || 29 || [[File:Green-beige palette.png]] || <code>j%3*2</code> for a more blue/beige variant, <code>-j%3*4</code> for beige/blue variant
|-
| <code>poke(16320+j,255/(1+2^(4+j%3-j/5)))</code> || 35 || [[File:Bright beige palette.png]] || <code>2*j%3</code> for a pink variant
|-
| <code>poke(16320+j,255/(1+2^(5-j%3-j/5)))</code> || 35 || [[File:Bright blue palette.png]] || <code>2*j%3</code> for a green variant
|-
| <code>poke(16320+j,s(j/15+s(j%3*3))^2*255)</code>|| 37 || [[File:Green-purple palette.png]] || Cyclic, based on [https://iquilezles.org/www/articles/palettes/palettes.htm]
|}

The last one is an entire family of palettes. You can replace <code>s(j%3*3)</code> with any function that depends on <code>j%3</code>; this ensures the palette remains cyclic. Some ideas for tweaking the palettes:
* Invert the colors by adding a <code>-1-</code> in the expression
* Flip the blue/red channels & have the entire palette running backwards by using <code>poke(16367-j,...)</code>
* Abuse the default Sweetie 16 palette, by only setting some of the RGB channels, while keeping others as they are. For example, setting all the blue channels to zero: <code>poke(16322+j*3,0)</code>. Here <code>j</code> is between 0 and 15.

Code for testing palettes:

<syntaxhighlight lang="lua">
function TIC()
cls()
for j=0,47 do poke(16320+j,s(j/15)*255)end
for c=0,15 do rect(c*5,0,5,5,c)end
end
s=math.sin
</syntaxhighlight>

== Motion blur ==

In TIC-80 API, the <code>pix</code> and <code>poke4</code> functions round numbers towards zero. This can be abused for a motion blur: <code>poke4(i,peek4(i)-.9)</code> maps colors 1 to 15 into one lower value, but value 0 stays at it is. Like so:

<syntaxhighlight lang="lua">
function TIC()
t=time()/9
circ(t%240,t%136,9,15)
for i=0,32639 do poke4(i,peek4(i)-.9)end
end
</syntaxhighlight>

== Updating only some pixels ==

Pixel-based effects, especially raycasting and raymarching, can become excessively slow. A simple trick to update only ~ half of the pixels, giving a dithered/motion blur look and making the update smoother:

<syntaxhighlight lang="lua">
function TIC()
t=time()/499
for i=t%2,32639,1.9 do poke4(i,i/4e3+t)end
end
</syntaxhighlight>

== Examples of effects ==

The effects have not been crunched to keep them readable.

=== Plasma ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/499
for i=0,32639 do
x=i%240
y=i/240
v=s(x/50+t)+s(y/22+t)+s(x/32)
poke4(i,v*2%8)
end
end
s=math.sin
</syntaxhighlight>

=== Rotozoomer ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/999
a=s(t-11)
b=s(t)
for i=0,32639 do
x=i%240-120
y=i/240-68
u=a*x-b*y
v=b*x+a*y
poke4(i,(u//1~v//1)//16)
end
end
s=math.sin
</syntaxhighlight>

=== Tunnel ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/199
for i=0,32639 do
x=i%240-s(t/7)*99-120
y=i/240-s(t/9)*49-68
u=math.atan2(y,x)*6/6.29
v=99/(x*x+y*y)^.5+t
poke4(i,u//1~v//1)
end
end
s=math.sin
</syntaxhighlight>

=== Raymarcher ===

The map is a bunch of repeated spheres here.

<syntaxhighlight lang="lua">
function TIC()
for i=0,32639 do
-- ray (u,v,w), not normalized!
u=i%240/120-1
v=i/32639-.5
w=1
-- camera origo (x,y,z)
x=3
y=0
z=time()/999 -- camera moves with time
j=0
repeat
X=x%6-3 -- domain repetition
Y=y%6-3
Z=z%6-3
-- ray not normalized=>reduce scale
m=(X*X+Y*Y+Z*Z)^.5/2-1
x=x+m*u
y=y+m*v
z=z+m*w
j=j+1
until j>15 or m<.1
poke4(i,j)
end
end
</syntaxhighlight>

== Additional Resources ==

* Code from past bytebattles https://livecode.demozoo.org/

Byte Battle

2022-02-19T09:10:48Z

Pestis: /* Basic optimizations */

== Bytebattles ==

Bytebattles are a form of live coding, similar to Shader Showdowns, where two contestants compete in writing a visual effect in 25 minutes. The coding environment is the [[Fantasy Consoles|TIC-80 fantasy console]]. However, unlike Shader Showdowns, there is an additional limit: the final code should be 256 characters or less. This requires the contestants to use efficient code (e.g. single letter variables) and to minimize the code (e.g. remove the whitespace), all within the time limit. Unlike in normal TIC-80 sizecoding, there is no compression, so every character counts.

== General notation in this article ==

{|
! Symbol || Meaning
|-
| <code>i</code> || Pixel index
|-
| <code>s</code> || Alias for math.sin
|-
| <code>x</code> || Pixel x-coordinate
|-
| <code>y</code> || Pixel y-coordinate
|}

== Basic optimizations ==

* Functions, that are called three or more times should be aliased. For example, <code>e=elli</code> with <code>e()e()e()</code> is 3 characters shorter than <code>elli()elli()elli()</code>. Functions with 5-character-long names may already benefit from aliasing with two calls: <code>r=rectb</code> with <code>r()r()</code> is 1 character shorter than <code>rectb()rectb()</code>.
* <code>t=0</code> with <code>t=t+.1</code> is 3 characters shorter than <code>t=time()/399</code>.
* <code>for i=0,32639 do x=i%240y=i/240 end</code> is 2-3 characters shorter than <code>for y=0,135 do for x=0,239 do end end</code>.
* <code>(x*x+y*y)^.5</code> is 6 characters shorter than <code>math.sqrt(x*x+y*y)</code>.
* <code>s(w-11)</code> and <code>s(w+8)</code> both approximate <code>math.cos(w)</code>, so only <code>math.sin</code> needs to be aliased. <code>s(w-11)</code> is far more accurate, with the cost of one more character.

== One-lining ==

Most whitespace can be removed from LUA code. For example: <code>x=0y=0</code> is valid. All new lines can be removed or replaced with space, making the whole code a single line:

<syntaxhighlight lang="lua">
function TIC()for i=0,32639 do poke4(i,i)end end
</syntaxhighlight>

'''Warning: Letters <code>a-f</code> and <code>A-F</code> after a number cause problems.''' <code>a=0b=0</code> is not valid code. It is advisable to only used one letter variables in the ranges <code>g-z</code> and <code>G-Z</code> from the start; this will make eventual one-lining easier.

== Load-function ==

Function <code>load</code> takes a string of code and returns a function with no named arguments, with the code as its body. It's particularly useful for shortening the TIC function after one-lining:

<syntaxhighlight lang="lua">
TIC=load'for i=0,32639 do poke4(i,i)end'
</syntaxhighlight>

As a rule of thumb, one-lining and using the load trick can bring a ~ 275 character code down to 256.

<code>load</code> can be even used to minimize a function with parameters: <code>...</code> returns the parameters. For example, the following example saves 3 bytes:

<syntaxhighlight lang="lua">
SCN=load'r=...poke(16320,r)'
</syntaxhighlight>

'''Warning: The backslash causes problems when using the load trick.''' In particular, if you have a string with escaped characters in the original code e.g. <code>print("foo\nbar")</code>, then this needs to be double-escaped: <code>load'print("foo\\nbar")'</code>

== Dithering ==

If you have a floating point color value, TIC-80 <code>pix</code> and <code>poke4</code> functions round it (toward zero). To add dithering, add a small value, between 0 and 1, to the color. The best technique depends whether you have <code>x</code> and <code>y</code> available or only <code>i</code> and how many bytes you can spare:

{|
! Expression || Length || Result || Notes
|-
| || || [[File:No dithering.png]] || No dithering
|-
| <code>s(i)*99%1</code> || 9 || [[File:Random dithering.png]] || "random" dithering, use *9 if desperate
|-
| <code>i*481/960%1</code> || 11 || [[File:Chess dithering.png]] || chess horse, <code>(x/2+y/4)%1</code> if you have x&y
|-
| <code>(x*2-y%2)%4/4</code> || 13 || [[File:Block dithering.png]] || 2x2 block dithering
|-
| <code>(i*2-i//80%2)%4/4</code> || 17 || [[File:Block dithering from i.png]] || 2x2 block dithering (almost), from i only
|}

A quick example demonstrating the 2x2 block dithering:

<syntaxhighlight lang="lua">
function TIC()
cls()
for i=0,2399 do
x=i%240
y=i//240
poke4(i,x/30+(x*2-y%2)%4/4)
end
end
</syntaxhighlight>

== Palettes ==

The following palettes assume that <code>j</code> goes from 0 to 47. Usually there's no need to make a new loop for this: just reuse another loop with <code>j=i%48</code>.

{|
! Expression || Length || Result || Notes
|-
| <code>poke(16320+j,j*5)</code> || 17 || [[File:Gray palette.png]] ||
|-
| <code>poke(16320+j,j%3*j*5)</code> || 21 || [[File:Blue-green-cyan palette.png]] || Good for objects & background
|-
| <code>poke(16320+j,j%3*j/.4)</code> || 22 || [[File:Blue palette.png]] || Use <code>(j+1)%3</code>, <code>(j+2)%3</code> or <code>2*j%3</code> for different colors
|-
| <code>poke(16320+j,s(j)^2*255)</code> || 24 || [[File:Rainbow palette.png]] || Change the phase of the palette with s(j+p)
|-
| <code>poke(16320+j,s(j)^2*j*6)</code> || 24 || [[File:Rainbow faded palette.png]] || Change the phase of the palette with s(j+p)
|-
| <code>poke(16320+j,s(j/15)*255)</code> || 25 || [[File:Blue-brown palette.png]] || <code>s(j/15)^2</code> is less bright
|-
| <code>poke(16320+j,s(j-j%-3)^2*255)</code> || 29 || [[File:Green-beige palette.png]] || <code>j%3*2</code> for a more blue/beige variant, <code>-j%3*4</code> for beige/blue variant
|-
| <code>poke(16320+j,255/(1+2^(4+j%3-j/5)))</code> || 35 || [[File:Bright beige palette.png]] || <code>2*j%3</code> for a pink variant
|-
| <code>poke(16320+j,255/(1+2^(5-j%3-j/5)))</code> || 35 || [[File:Bright blue palette.png]] || <code>2*j%3</code> for a green variant
|-
| <code>poke(16320+j,s(j/15+s(j%3*3))^2*255)</code>|| 37 || [[File:Green-purple palette.png]] || Cyclic, based on [https://iquilezles.org/www/articles/palettes/palettes.htm]
|}

The last one is an entire family of palettes. You can replace <code>s(j%3*3)</code> with any function that depends on <code>j%3</code>; this ensures the palette remains cyclic. Some ideas for tweaking the palettes:
* Invert the colors by adding a <code>-1-</code> in the expression
* Flip the blue/red channels & have the entire palette running backwards by using <code>poke(16367-j,...)</code>
* Abuse the default Sweetie 16 palette, by only setting some of the RGB channels, while keeping others as they are. For example, setting all the blue channels to zero: <code>poke(16322+j*3,0)</code>. Here <code>j</code> is between 0 and 15.

Code for testing palettes:

<syntaxhighlight lang="lua">
function TIC()
cls()
for j=0,47 do poke(16320+j,s(j/15)*255)end
for c=0,15 do rect(c*5,0,5,5,c)end
end
s=math.sin
</syntaxhighlight>

== Motion blur ==

In TIC-80 API, the <code>pix</code> and <code>poke4</code> functions round numbers towards zero. This can be abused for a motion blur: <code>poke4(i,peek4(i)-.9)</code> maps colors 1 to 15 into one lower value, but value 0 stays at it is. Like so:

<syntaxhighlight lang="lua">
function TIC()
t=time()/9
circ(t%240,t%136,9,15)
for i=0,32639 do poke4(i,peek4(i)-.9)end
end
</syntaxhighlight>

== Updating only some pixels ==

Pixel-based effects, especially raycasting and raymarching, can become excessively slow. A simple trick to update only ~ half of the pixels, giving a dithered/motion blur look and making the update smoother:

<syntaxhighlight lang="lua">
function TIC()
t=time()/499
for i=t%2,32639,1.9 do poke4(i,i/4e3+t)end
end
</syntaxhighlight>

== Examples of effects ==

The effects have not been crunched to keep them readable.

=== Plasma ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/499
for i=0,32639 do
x=i%240
y=i/240
v=s(x/50+t)+s(y/22+t)+s(x/32)
poke4(i,v*2%8)
end
end
s=math.sin
</syntaxhighlight>

=== Rotozoomer ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/999
a=s(t-11)
b=s(t)
for i=0,32639 do
x=i%240-120
y=i/240-68
u=a*x-b*y
v=b*x+a*y
poke4(i,(u//1~v//1)//16)
end
end
s=math.sin
</syntaxhighlight>

=== Tunnel ===

<syntaxhighlight lang="lua">
function TIC()
t=time()/199
for i=0,32639 do
x=i%240-s(t/7)*99-120
y=i/240-s(t/9)*49-68
u=math.atan2(y,x)*6/6.29
v=99/(x*x+y*y)^.5+t
poke4(i,u//1~v//1)
end
end
s=math.sin
</syntaxhighlight>

=== Raymarcher ===

The map is a bunch of repeated spheres here.

<syntaxhighlight lang="lua">
function TIC()
for i=0,32639 do
-- ray (u,v,w), not normalized!
u=i%240/120-1
v=i/32639-.5
w=1
-- camera origo (x,y,z)
x=3
y=0
z=time()/999 -- camera moves with time
j=0
repeat
X=x%6-3 -- domain repetition
Y=y%6-3
Z=z%6-3
-- ray not normalized=>reduce scale
m=(X*X+Y*Y+Z*Z)^.5/2-1
x=x+m*u
y=y+m*v
z=z+m*w
j=j+1
until j>15 or m<.1
poke4(i,j)
end
end
</syntaxhighlight>

== Additional Resources ==

* Code from past bytebattles https://livecode.demozoo.org/