rainbow generator

Community Forums/Showcase/rainbow generator

RemiD

(Posted 2016) [#1]

Hello, :)

Just playing with Blitz3d to see if i could reproduce a rainbow in 3d with a mesh (made of several arcs) and vertices colors :

with a grey sky :

with a blue sky :

animated gif :
rd-stuff.fr/rainbow-generator-(greysky)-500w312h-10fps.gif

source code here : http://www.blitzbasic.com/codearcs/codearcs.php?code=3288

Rick Nasher

(Posted 2016) [#2]

Nice piece of code. But appears the blue sky filters out the other colors.
I did a quick experiment and changed the '3' to '1' as you suggested in below line which gives a brighter colored result - at least on my system.

EntityBlend(Rainbow_Mesh,1)  ;1 or 3

Now let's add some clouds, sun, rain hills, trees a few rabbits and we're in Teletubby land ;-)

Rick Nasher

(Posted 2016) [#3]

Btw: I couldn't locate the pot of gold at the end of the raibow..

RemiD

(Posted 2016) [#4]

Yes it looks better with a grey/white sky.

With a whiter sky it is better to use blendmode alpha (1) instead of blendmode add (3)

Btw: I couldn't locate the pot of gold at the end of the raibow..

take a look at that :
en.wikipedia.org/wiki/Rainbow#Full-circle_rainbow
it may help : ;)

Rick Nasher

(Posted 2016) [#5]

Ah that explains it all. :-) Or.. perhaps the leprechaun can only be found when in Ireland?

Blitzplotter

(Posted 2016) [#6]

nice work, to be sure ;)

RemiD

(Posted 2016) [#7]

More for fun than for a real need ;)

I bet it could look even nicer with a glow effect on it...

Hardcoal

(Posted 2016) [#8]

Fun is a need :)
And sometimes best things comes from the need for fun :p
Plus, who doesn't like rainbows..
Ask Noah

Bobysait

(Posted 2016) [#9]

Nice looking.
Perhaps you could/should skip vertexcolor (for once ^_^) and use a texture instead (a single row texture like 8*1 pixels)

And by the way, the arc equation is pretty simple to implement, you'll save yourself a lot of time by just using cos/sin instead of all this pivot stuff

(a small sample of using a texture -> it also use alpha on the texture to fade the borders)

Graphics3D 800,600,0,2
SetBuffer BackBuffer()

AmbientLight		( 0,0,0 )

Local Light		=	CreateLight		( 2 )
					MoveEntity		( Light, 100,400,500 )
					LightRange		( Light, 1500 )
					
Local Cam		=	CreateCamera	( )
					MoveEntity		( Cam, 0,5,0 )
					CameraClsColor	( Cam, 100,150,220 )
					
Local Ground	=	CreatePlane		( 8 )
					EntityColor		( Ground, 20,50,10 )

; Rainbow Texture
	Local RTex		=	CreateTexture	( 8, 2, 3+32 ) ; 1+2 -> color + alpha (32-> clamp V)
						SetBuffer TextureBuffer(RTex)
							LockBuffer()
								For j = 0 To 1
									Local RainbowCA% = $00000000 ; first row is alpha 0
									If j = 1 Then RainbowCA = $FF000000 ; second row is alpha 255
									WritePixelFast 0,j, $00000000 + $A000FF ; alpha 0 (mix between first and last color)
									WritePixelFast 1,j, RainbowCA + $FF0000 ; Red
									WritePixelFast 2,j, RainbowCA + $FF8000 ; Orange
									WritePixelFast 3,j, RainbowCA + $FFFF00 ; Yellow
									WritePixelFast 4,j, RainbowCA + $50FF50 ; Green
									WritePixelFast 5,j, RainbowCA + $0080FF ; Blue
									WritePixelFast 6,j, RainbowCA + $0000FF ; Indigo
									WritePixelFast 7,j, RainbowCA + $8000FF ; Violet
								Next
							UnlockBuffer()
						SetBuffer BackBuffer()

; Rainbow setup
	; Rainbow Radius
	Local RainbowR#	=	100.0
	Local RainbowA0# =	-75.0 ; Arc From Angle A0 To Angle A1
	Local RainbowA1# =	75.0
	; Rainbow Width ( "linewidth" )
	Local RainbowW#	=	16.0
	; Details ( Arcs )
	Local RainbowSeg%=	64 ; you can decrease this to 20-30, but we will start spotting the segments ^^

; Rainbow Mesh
	Local Rainbow	=	CreateMesh		( )
						; you can use fx 16 to draw the 2 sides of the triangles (here the rainbow is in front of the camera, so it's useless )
						EntityFx		( Rainbow, 1+8 ) ; fullbright and disable fog
						; you can use blend 1 or 3 (1 will be more solid but less lighted)
						EntityBlend		( Rainbow, 3 )
						; you can also use EntityAlpha to fade the rainbow
						EntityTexture	( Rainbow, RTex ) ; use the rainbow texture
						PositionEntity	( Rainbow, 0,-30,150 ) ; move it far enough so we can see it
	Local Surf		=	CreateSurface	( Rainbow )
	Local NSeg		=	16
	Local n, Ang
	
	; draw an arc
	For n = 0 To RainbowSeg
		Local DAng# = Float(n)/RainbowSeg;
		Local rx# = Cos(90 + RainbowA0 + (RainbowA1-RainbowA0)*DAng);
		Local ry# = Sin(90 + RainbowA0 + (RainbowA1-RainbowA0)*DAng);
		Local tv# = Sin(n*180 / RainbowSeg); define the tex V coord (lower = more alpha) -> tweak this equation to create different effects
		; outer vertex
		AddVertex Surf, RainbowR*rx, RainbowR*ry, 0, 0.05, tv
		;For inner vertex U tiles a bit to get the alpha of first pixel
		AddVertex Surf, (RainbowR-RainbowW)*rx, (RainbowR-RainbowW)*ry, 0, 1.07, tv
		; build the triangle strip
		If n>0
			AddTriangle (Surf, n*2-2, n*2-1, n*2+1)
			AddTriangle (Surf, n*2-2, n*2+1, n*2)
		EndIf
	Next


Repeat
	RenderWorld()
	Flip True
Until KeyDown(1)
End

The mesh is composed of a single "line" of triangle (a triangle strip), so you can get higher details with lower triangles. (just notice that below 25 for RainbowSeg, you'll start to see the segment)

RemiD

(Posted 2016) [#10]

@Bobysait>>yes i could have used another approach to create the arcs but i do what i can with what i know :P

Nice example too. :)

RemiD

(Posted 2016) [#11]

It is weird how that even with the same alpha, the same blendmode, the same background color, the result does not seem to look the same...

RemiD

(Posted 2016) [#12]

Forget about what i said (in post#11), using the same alpha, the same blendmode, the same background color, the results look similar :

Hardcoal

(Posted 2016) [#13]

AdamStrange

(Posted 2016) [#14]

@RemiD The second image (the one on the right) has a very nice 'smooth' look to it, plus the nice fade towards the bottom.

the other one has a blocky feel - you can see the geometry underneath it. - looks like 9 segments on the left?

Me preference would be the one on the right as it has a professional look to it. The blocky one feels a bit cheap in comparison...

RemiD

(Posted 2016) [#15]

The one at right is the example by Bobysait
The one at left is my example

However you can add more sections to have a more round shape, no worry, just edit the code !

I find interesting how it is possible to achieve a similar result using only a mesh and vertices colors, or with a mesh and texels colors (a texture)

RemiD

(Posted 2016) [#16]

less blocky more roundy version for Adam :

and you can also understand how it is made with the wire view.