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## 3D Perlin Noise Map Ridges

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### #1kennyb2142  Members

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Posted 13 October 2011 - 06:45 PM

Hey so, I've been reading everything I can find on how to use the 3d perlin noise to generate overhangs and ridges but I seem to be not on the right track?
This is what I got using this method:
Add two perlin octaves together. If they are under 0 I turn them into blocks. If they are over 0 I continue and move on to the next one.

Once the sum is under 0, I add the amplitude to them and then proceed. If they are under the water level I draw a lake/ocean over that certain level.. But
It seems I'm missing something, there are lots of random blocks everywhere and only some attached ridges.

It used to look like this with my old method:

What could I doing wrong? Here's my code for creating cubes:
for (byte chunkX = 0; chunkX < xyChunks; chunkX++)
{
for (byte chunkY = 0; chunkY < xyChunks; chunkY++)
{
biomeType = r.Next(0, 5);
for (int xAxis = 0 + (16 * (int)chunkX); xAxis < chunkWidth + (16 * (int)chunkX); xAxis++)
{
for (int yAxis = 0 + (16 * (int)chunkY); yAxis < chunkLength + (16 * (int)chunkY); yAxis++)
{
for (int zAxis = 0; zAxis < 5; zAxis++)
{
//15,10 | 30, 8 | 20, 5 <----- Octave 4/5 combos that are good so far
//float octave1 = PerlinSimplexNoise.noise((xAxis + worldSeed), (yAxis + worldSeed), 1, 0.0001f);
//float octave2 = PerlinSimplexNoise.noise((xAxis + worldSeed), (yAxis + worldSeed), 1, 0.0005f);
//float octave3 = PerlinSimplexNoise.noise((xAxis + worldSeed), (yAxis + worldSeed), 1, 0.005f);
float octave4 = PerlinSimplexNoise.noise((xAxis + worldSeed), (yAxis + worldSeed), zAxis, 0.009f);
float octave5 = PerlinSimplexNoise.noise((xAxis + worldSeed), (yAxis + worldSeed), zAxis, 0.03f);

//float cubeGroundBase = octave1 + octave2 + octave3 + octave4 + octave5;
float cubeGroundBase = octave4 + octave5;
if (cubeGroundBase > 0)
continue;

octave4 *= 20f;
octave5 *= 5f;

cubeGroundBase = octave4 + octave5;
if (67 + cubeGroundBase < 59)
cubeGroundBase = -8;

if ((67 + (int)cubeGroundBase) <= 64) //Check if water
{
int sandLevel = (waterLevel + 3) + (int)cubeGroundBase; //update sand level from base

Sand[chunkX, chunkY].Add(new Vector3(xAxis, sandLevel, yAxis)); //Add to water list

cubeCollision[chunkX, chunkY][xAxis, yAxis].Add(new BoundingBox(new Vector3(xAxis - .5f, sandLevel - .5f, yAxis - .5f)
, new Vector3(xAxis + .5f, sandLevel + .5f, yAxis + .5f))); //add bounding box to list

Water[chunkX, chunkY].Add(new Vector3(xAxis, waterLevel, yAxis)); //Also add to list
}
else //it's grass or dirt
{
int groundLevel = groundBase + (int)cubeGroundBase; //update ground level with base

Grass[chunkX, chunkY].Add(new Vector3(xAxis, groundLevel, yAxis)); //Add grass to list

cubeCollision[chunkX, chunkY][xAxis, yAxis].Add(new BoundingBox(new Vector3(xAxis - .5f, groundLevel - .5f, yAxis - .5f)
, new Vector3(xAxis + .5f, groundLevel + .5f, yAxis + .5f))); //add cubeboundingbox to list

Dirt[chunkX, chunkY].Add(new Vector3(xAxis, groundLevel - 1, yAxis)); //Add grass to list
}
}
}
}
}
}


I'm only doing 5 for the height? I'm not sure if that's even how you would go about doing this?

### #2kennyb2142  Members

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Posted 14 October 2011 - 08:04 PM

Anyone? I'm still trying to figure this out and I don't think I'm grasping the concept

### #3Suspense  Members

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Posted 15 October 2011 - 11:29 AM

How did your old method work? What did you change from then to now?

### #4kennyb2142  Members

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Posted 17 October 2011 - 09:15 PM

How did your old method work? What did you change from then to now?

Hey, thanks for the reply my old method was not using the "density" idea, I just sent the x and y coords into the perlin noise then multiplied them and used the result for the cube height.

Now though I gave up on the density and added an octave using the old method (and modified it a little to give more variation) to produce maps like this:

Although I'm still trying to figure out the whole cliffs and overhangs thing if you could give me some pointers from here?

### #5Calneon  Members

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Posted 19 October 2011 - 08:22 PM

Is it something like this you're after?

That's done by adding 3d noise to a 2d heightmap. The 3d noise is generated like you would 2d noise, just with a third dimension (im sure you'll find ways to do this).

### #6kennyb2142  Members

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Posted 06 June 2012 - 08:11 PM

Is it something like this you're after?

That's done by adding 3d noise to a 2d heightmap. The 3d noise is generated like you would 2d noise, just with a third dimension (im sure you'll find ways to do this).

Yeah that's what I want, but I'm so confused.. What value do I input for the third dimension? And how do I go about looping the perlin values.. like x, y, then z?

### #7jefferytitan  Members

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Posted 06 June 2012 - 09:09 PM

I gather that Calneon's approach is to generate a 2D heightmap so that there is a general landscape (no caves etc). After that they generate a 3D Perlin noise field which is only used for subtracting from the existing landscape. So you literally generate a "density change" figure for every x, y, z. If that co-ordinate is already empty, you ignore it (you don't want lumps of rock just hanging in the air). If the co-ordinate contains rock you remove that rock if the Perlin noise at that spot exceeds a certain threshold. You could of course increase or decrease density of the rock as well, to allow a more interesting digging or erosion mechanic.

### #8winsrp  Members

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Posted 19 June 2012 - 12:15 PM

that kind of landscape is not hard to make, took me a while to figure it out also, worst than a company secrect, no one want to tell

you need to use a 3d perlin function, in combination with a 2d perlin function.

whit 2d perlin you make a height map, just like you are now. So you probably do something like

for x = 0 to widht
for z = 0 to depth
get perlin 2d for height
for y = 0 to perlin2d
make cube


In order to add the 3d, you need to call one 3d perlin value and use it as density.

for x = 0 to widht
for z = 0 to depth
get perlin 2d for height
for y = 0 to perlin2d
get perlin 3d for density
if density > 0 then
make cube.


You would normally also want to use the perlin 3d after you have some ground under you, otherwise you will get empty spaces as in your first screen.

for x = 0 to widht
for z = 0 to depth
get perlin 2d for height
for y = 0 to perlin2d
if y > waterlevel+(some number lets say 8, so you have some nice beach)
get perlin 3d for density
if density > 0 then
make cube.
else
make cube (density is not important on lower levels)


Now in order to avoid some of the anoying floating islands you just apply a gradient to the density of the 3d perlin such as

for x = 0 to widht
for z = 0 to depth
get perlin 2d for height
for y = 0 to perlin2d
if y > waterlevel+(some number lets say 8, so you have some nice beach).
get perlin 3d for density
if (density*(1-gradient)) > 0 then
make cube.
else
make cube (density is not important on lower levels)

.

Which this you will have your 3d terrain in no time.

Calneon, how the hell you did the lighting... that thing is killing me....

Edited by winsrp, 19 June 2012 - 12:16 PM.

### #9JTippetts  Moderators

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Posted 19 June 2012 - 09:04 PM

I wrote a couple articles about this type of thing some time back, that served as the basis for an article in Game Developer magazine. I also re-wrote the thing for my Accidental library, if you are interested.

### #10Alrik  Members

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Posted 21 June 2012 - 05:45 AM

hi,
i don't understand this lines of code:

get perlin 2d for height
for y = 0 to perlin2d

perlin returns a value between 0 and 1 so how do you implement the for statement?
i also try to create such a world like on the screenshot but it looks strange.

### #11winsrp  Members

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Posted 21 June 2012 - 11:30 AM

well perlin normally return a number from -1 to 1.. if yours returns from 0 to 1, then maybe some conversions have been applied to it.

something like (0.5 + 0.5 * perlin value.)

and that line means set a variable with the perlin height number

normaly in this step you would also the above transformation and a height amplification

like (0.5 + 0.5 * perlin value.)* max height value.

Then make a look from 0 to the pelin value, assuming that your height array starts at 0. where 0 value = bottom of the world, some number in between lets say 64 = water level and 128 would be something like the highest mountain value.

Edited by winsrp, 21 June 2012 - 11:33 AM.

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