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Cart #bc_cloud_parallax-0 | 2025-03-04 | Code ▽ | Embed ▽ | No License
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tline-GFX for practice and understanding.

https://www.lexaloffle.com/bbs/?tid=147597
I will share the code used in this post to implement it step by step.
Coding the ideal effect all at once can be complicated and difficult to implement.
Isolating all the elements and solving them one by one will bring you closer to your goal.

Step1

Draw one line from top to bottom with tline().

 
bottom=127

for i=0,bottom do
	tline(0,i,127,i,0,i/8)
end

Step2

Shift the reference y coordinate so that it scrolls from bottom to top.

 
bottom=127
t=time()*4

for i=0,bottom do
	tline(0,i,127,i,0,t+i/8)
end

Step3

Stretch the bottom edge to the same size as the screen, and stretch the top edge to twice that size.

 
width=128
swidth=256
sw=swidth/width

d=(1-1/sw)/8/height --creates a transition that doubles the width (default: 1tile/8).
for i=0,bottom do
	tline(0,i,127,i,0,i/8,(1/8/sw+d*i)) --0.5/8 to 1/8(default)
end

Step4

Slide it to the left to adjust it to a trapezoid.

 
width=128
swidth=256
sw=swidth/width

height=128
left=32

l=(swidth-width-left)/2/sw
dl=l/height --creates a change in the slide that halves the amount of change
d=(1-1/sw)/8/height --creates a transition that doubles the width (default: 1tile/8).
for i=0,height-1 do
	tline(0,i,127,i,(l-dl*i)/8,i/8,(1/8/sw+d*i)) --0.5/8 to 1/8
end

Step5

Stretch display height.

 
height=128
sheight=64
sh=sheight/height

for i=0,sheight-1 do
	y=i/sh
	tline(0,i,127,i,0,y/8)
end

Step6

Combine all the steps.

 
width=128
swidth=256
sw=swidth/width

height=128
sheight=64
sh=sheight/height

t=time()*4

l=(swidth-width-left)/2/sw
dl=l/height --creates a change in the slide that halves the amount of change
d=(1-1/sw)/8/height --creates a transition that doubles the width (default: 1tile/8).
for i=0,sheight-1 do
	y=i/sh
	tline(0,i,127,i,(l-dl*i)/8,t+y/8,(1/8/sw+d*i)) --0.5/8 to 1/8
end

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