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surface normals

Started by Chaucer Mar 6, 2003 at 5:14 PM 2 replies 350+ views

Original Post

Mar 6, 2003 at 5:14 PM

Hello, I''m having a problem getting my surface normals on my terrain to be correct. I''m creating my vertices like this. 2--3 0--1 in this order 0-1-2 2-1-3 I''m calculating surface normals like this:

  
void Terrain::FindNormals()
{
	int count=0;
	for(int j=0;j<GetNumVertices()/3;j++)
	{
		D3DXVECTOR3 vertex[3];
		vertex[0] = m_pVertices[count+0].position;
		vertex[1] = m_pVertices[count+2].position;
		vertex[2] = m_pVertices[count+1].position;
		CalculateNormal(vertex, &m_pVertices[count+0].normal);
		count+=3;
	}
}

here''s my calculate normal function:

  
void CalculateNormal(D3DVECTOR v[3], D3DVECTOR *normal)
{
	D3DVECTOR a, b;

	a.x = v[0].x - v[1].x;
	a.y = v[0].y - v[1].y;
	a.z = v[0].z - v[1].z;

	b.x = v[0].x - v[2].x;
	b.y = v[0].y - v[2].y;
	b.z = v[0].z - v[2].z;

	//find cross product to get the normal

	normal->x = (a.y*b.z) - (a.z*b.y);
	normal->y = (a.z*b.x) - (a.x*b.z);
	normal->z = (a.x*b.y) - (a.y*b.x);

	D3DXVec3Normalize((D3DXVECTOR3*)normal, (D3DXVECTOR3*)v);			
}

Can anyone see where I''m not getting it right? Thanks.

emptyhead

Mar 6, 2003 at 5:21 PM

quote:

D3DXVec3Normalize((D3DXVECTOR3*)normal, (D3DXVECTOR3*)v);

I think you mean:
D3DXVec3Normalize(normal, normal);

emptyhead
Watch out for advice from the successfull, they don''t want company

Chaucer

Mar 6, 2003 at 5:45 PM

Thanks. That helps but now I''m only getting strips of lit terrain instead of nothing on the terrain being lit.

Osc

Mar 7, 2003 at 8:56 AM

You''re only setting the normal for one in every three vertices...

  
D3DXVECTOR3 vertex[3];
vertex[0] = m_pVertices[count+0].position;
vertex[1] = m_pVertices[count+2].position;
vertex[2] = m_pVertices[count+1].position;

D3DXVECTOR3 normal;
CalculateNormal(vertex, &normal);

m_pVertices[count+0].normal = normal;
m_pVertices[count+1].normal = normal;
m_pVertices[count+2].normal = normal;

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