Coherent perlin noise on a sphere

[Padman]

Hi,

I'm doing a planet generator for my game. But I've some problems with the c++ libnoise.

I successfully generated a quadtree (maybe with a bad algo... ^^') and successfully transformed it into a sphere according to this great blog.

 

But now, I want to apply a perlin noise using the c++ libnoise library. But the render is not really good... But I think I'm in the right way. My problem is about the noise coherence between each faces of my cube. The faces are not joined. Here is a screenshot.

 

 

I do this following code to generate one face of my cube :

//generating the front face...
Surface* frontFace = model->AddSurface();
for(int i = 0 ; i<numSquare ; i++)
{
 for(int j = 0 ; j<numSquare ; j++)
 {
	 float x = -1+i*segment;
	 float y = -1+j*segment;
	 float z = -1;
	 float dx = (x * sqrtf(1.0 - (y*y/2.0) - (z*z/2.0) + (y*y*z*z/3.0))) * Radius; //transform into sphere
	 float dy = (y * sqrtf(1.0 - (z*z/2.0) - (x*x/2.0) + (z*z*x*x/3.0))) * Radius;
	 float dz = (z * sqrtf(1.0 - (x*x/2.0) - (y*y/2.0) + (x*x*y*y/3.0))) * Radius;
	 float ndz = dz + perlinModule.GetValue(dx,dy,dz);//generate noise
	 int v0 = frontFace->AddVertex(dx,dy,ndz);
	 x = -1+(i*segment)+segment;
	 y = -1+j*segment;
	 z = -1;
	 dx = (x * sqrtf(1.0 - (y*y/2.0) - (z*z/2.0) + (y*y*z*z/3.0))) * Radius;
	 dy = (y * sqrtf(1.0 - (z*z/2.0) - (x*x/2.0) + (z*z*x*x/3.0))) * Radius;
	 dz = (z * sqrtf(1.0 - (x*x/2.0) - (y*y/2.0) + (x*x*y*y/3.0))) * Radius;
	 ndz = dz + perlinModule.GetValue(dx,dy,dz);
	 int v1 = frontFace->AddVertex(dx,dy,ndz);
	 x = -1+(i*segment)+segment;
	 y = -1+(j*segment)+segment;
	 z = -1;
	 dx = (x * sqrtf(1.0 - (y*y/2.0) - (z*z/2.0) + (y*y*z*z/3.0))) * Radius;
	 dy = (y * sqrtf(1.0 - (z*z/2.0) - (x*x/2.0) + (z*z*x*x/3.0))) * Radius;
	 dz = (z * sqrtf(1.0 - (x*x/2.0) - (y*y/2.0) + (x*x*y*y/3.0))) * Radius;
	 ndz = dz + perlinModule.GetValue(dx,dy,dz);
	 int v2 = frontFace->AddVertex(dx,dy,ndz);
	 x = -1+i*segment;
	 y = -1+(j*segment)+segment;
	 z = -1;
	 dx = (x * sqrtf(1.0 - (y*y/2.0) - (z*z/2.0) + (y*y*z*z/3.0))) * Radius;
	 dy = (y * sqrtf(1.0 - (z*z/2.0) - (x*x/2.0) + (z*z*x*x/3.0))) * Radius;
	 dz = (z * sqrtf(1.0 - (x*x/2.0) - (y*y/2.0) + (x*x*y*y/3.0))) * Radius;
	 ndz = dz + perlinModule.GetValue(dx,dy,dz);
	 int v3 = frontFace->AddVertex(dx,dy,ndz);
	 frontFace->AddTriangle(v2,v1,v0);
	 frontFace->AddTriangle(v0,v3,v2);
 }
}

 

I don't know how to solve this. I didn't find good explanations on the web. I'm not really good in maths but I've some logic ideas (I think ...), it's a miracle if this code works xD. Maybe it's my cube generation algorythm which is bad...

I understood that some others use a lerp function to join "smoothly" each faces, but I don't know how I can apply this to my code. ^^' If someone can help it would be great.

Thx !

 

PS: I'm french so really sorry for my english

[shadmar]

It will fail if your box dimentions are greater than 1.

This works in lua : http://www.leadwerks.com/werkspace/topic/10244-lua-tip-box-to-sphere/page__hl__lua+tip

[Padman]

Thanks for your help. But I aldready know that ^^'. Sorry if I don't explain correctly my problem. My problem is to apply a perlin noise on my sphere. I don't know how to generate a coherent noised sphere. In my screenshot, all my cube faces are separated. I don't know how to join them "smoothly".

[shadmar]

I dont know, use tileable noise?

http://gamedev.stackexchange.com/questions/23625/how-do-you-generate-tileable-perlin-noise

[Guppy]

It seems that your problem is that you have double verticies along your edges ( zooming in this also seems to cause gaps ) you should either merge them or store them and look it up.

 

But I think It may just be easier to take a different approach all together to creating the sphere

[Padman]

Thank you for your help Guppy. You're right, I have double vertices on my edges because of my bad quadtree generator algorythm ^^. So I recoded it and now I can have a perfect noised sphere. Thank you all for your help. Now ... I have to apply textures on my planet according to the height of my vertices... It's time to work hard (and first read some docs). ^^