Perlin noise

Blitz3D Forums/Blitz3D Programming/Perlin noise

MusicianKool

(Posted 2010) [#1]

So I have a small 2d PN Generator but I want to get interpolation to work. can't quite figure it out.

Graphics3D 800,600,32,2 
SetBuffer BackBuffer()
Global size = 128*2
octaves = 8
Dim noise#(size-1,size-1,octaves-1)
img = CreateImage(size,size)
ig = ImageBuffer(img)

For o = 0 To octaves -1
	For x = 0 To (size/(o+1)-1)
		For y = 0 To (size/(o+1)-1)
			r#= Float (Float Rnd(0,1)*Float(Float 1/Float octaves))
			noise#(x,y,o)= r#
		Next
	Next	
Next


LockBuffer(ig)

For x = 0 To size-1
	For y = 0 To size-1
		For o = 0 To octaves - 1
			x1# = Float x/(Float o+1)
			y1# = Float y/(Float o+1)
			x2# = Float x/(Float o+1)+1
			y2# = Float y/(Float o+1)+1
			If x2# > size-1 Then x2# = 0
			If y2# > size-1 Then y2# = 0
			
			avg# = smooth#(x,y,o)
			x3 = x+1
			y3 = y+1
			If x3 > size-1 Then x3 = 0
			If y3 > size-1 Then y3 = 0
			avg1# = smooth#(x,y,o)
			avg2# = smooth#(x3,y,o)
			avg3# = smooth#(x,y3,o)
			avg4# = smooth#(x3,y3,o)
			
			tx# = x1# - Int(x1#)
			a# = interpolate#(avg1#,avg2#,tx#)
			b# = interpolate#(avg3#,avg4#,tx#)

			ty# = y1# - Int(y1#)
			t# = interpolate#(a#,b#,ty#)

			;t# = t# + noise#(x1#,y1#,o)
			;t# = t# + avg#
		Next
		col = 255 * t#
		If col > 255 Then col = 255
		If col < 0 Then col = 0
		WritePixelFast x,y,getArgb(col,col,col),ig
		t# = 0
	Next
Next

UnlockBuffer(ig)

DrawImage img,0,0:Flip
WaitKey()
End

Function GetARGB(r,g,b):		Return b Or(g Shl 8)Or(r Shl 16):	End Function

Function Interpolate#(a#, b#, x#)
	Return  a*(1-x) + b*x
End Function

Function Smooth#(x,y,o)
	tx1 = (x - 1)/(Float o+1)
	ty1 = (y - 1)/(Float o+1)
	tx2 = (x + 1)/(Float o+1)
	ty2 = (y + 1)/(Float o+1)
	x = x/(Float o+1)
	y = y/(Float o+1)
	If x = 0 Then tx1 = size-1
	If y = 0 Then ty1 = size-1
	If x = size-1 Then tx1 = 0
	If y = size-1 Then ty1 = 0
	If x = 0 Then tx2 = size-1
	If y = 0 Then ty2 = size-1
	If x = size-1 Then tx2 = 0
	If y = size-1 Then ty2 = 0
	avg# = 0
	avg# = noise#(tx1,ty1,o)+avg#
	avg# = noise#(x,ty1,o)+avg#
	avg# = noise#(tx2,ty1,o)+avg#
	avg# = noise#(tx1,y,o)+avg#
	avg# = noise#(x,y,o)+avg#
	avg# = noise#(tx2,y,o)+avg#
	avg# = noise#(tx1,ty2,o)+avg#
	avg# = noise#(x,ty2,o)+avg#
	avg# = noise#(tx2,ty2,o)+avg#
	Return avg#/9
End Function

Charrua

(Posted 2010) [#2]

how do you know that isn't working, i don't understand your problem.
is your code?
seen your signature music, octaves and then pixels?
are you tring to do something with textures or for audio?

when a run the example i see a randomized image, gray scale, ok you use the same color for r,g,b. Against what can i compare the result to know isn't ok?

if you spect some smoothed values, the problem should be in the operations between floats and integers, their when mixed in operations give us some headaches, but i see some floats and seems to be carefully written.

Juan

MusicianKool

(Posted 2010) [#3]

I'm trying to achieve a smooth height map.

like the image from
http://freespace.virgin.net/hugo.elias/models/m_perlin.htm

instead it ends up blocks, and it's because of the incorrect usage of linear interpolation. Maybe it's because I'm adding them backwards I really don't know.

Charrua

(Posted 2010) [#4]

when averagin in the for o=0 to Octaves-1 .. loop
you only use the last interpolate value: t# = interpolate#(a#,b#,ty#)
i think that the rest should be accumulated:
t# = t# + interpolate#(a#,b#,ty#)

but this is just a "may be" really i don't know the basis of the algorithm.

modifying this line, the image is better, using Octaves=16 or 32 implies more smoothed (averaged) pictures.

Juan