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Terrain Normals

Started by guts Jul 14, 2003 at 8:04 AM 3 replies 450+ views

Original Post

Jul 14, 2003 at 8:04 AM

Hi! I''m currently calculating vertices, texcoords and indices this way:

	bool SwitchSides = true;
	for(int x=0;x<=size-2;x+=step)
	{
		if(SwitchSides)
		{
			for(int y=size-1;y>=0;y-=step)
			{
				mpVertices[mNumVer].x = x;
				mpVertices[mNumVer].y =(int)GetHeight(x, y); 
				mpVertices[mNumVer].z =y;                
				mpTexcoords[mNumVer].x = mpVertices[x1].x / (float)size;
				mpTexcoords[mNumVer].y = mpVertices[x1].z / (float)size;
				mNumVer++;

				mpVertices[mNumVer].x = x + step;  
				mpVertices[mNumVer].y = (int)GetHeight(x + step, y);
				mpVertices[mNumVer].z = (int)y; 
				mpTexcoords[mNumVer].x = mpVertices[x1].x / (float)size; 
				mpTexcoords[mNumVer].y = mpVertices[x1].z / (float)size;
				mNumVer++;                                 
			}
		} 
		else 
		{
			for(int y=0;y<=size-1;y+=step)
			{
				mpVertices[mNumVer].x = x + step;  
				mpVertices[mNumVer].y =(int)GetHeight(x + step, y);
				mpVertices[mNumVer].z =(int) y;                          
				mpTexcoords[mNumVer].x = mpVertices[x1].x / (float)size; 
				mpTexcoords[mNumVer].y = mpVertices[x1].z / (float)size;  
				mNumVer++;

				mpVertices[mNumVer].x = (int)x;  
				mpVertices[mNumVer].y = (int)GetHeight(x, y);
				mpVertices[mNumVer].z = (int)y; 
				mpTexcoords[mNumVer].x = mpVertices[x1].x / (float)size; 
				mpTexcoords[mNumVer].y = mpVertices[x1].z / (float)size;
				mNumVer++;
			}
		}
		SwitchSides = !SwitchSides;
	}


	int idx = 0;
	mNumInd = mNumVer;
	mpIndices = new int[mNumInd];

	for (idx=0; idx < mNumInd; idx++)
		mpIndices[idx] = idx;
[/CODE]

My problem is that I don''t have an idea how to calculate normals for triangle strips.
Maybe this sounds kind of impertinent, but would somebody please post the source code that calculates these normals (I tried it for a long time and now I''m really sick of this...)

thanks in advance ...
guts

Zorodius

Jul 14, 2003 at 8:10 AM

The normal of a triangle is the cross product of two of its sides taken as vectors from a common vertex. (more info)

"Last time, I asked: ''What does mathematics mean to you?'' And some people answered: ''The manipulation of numbers, the manipulation of structures.'' And if I had asked what music means to you, would you have answered: ''The manipulation of notes?''" - S. Lang

guts

Jul 15, 2003 at 5:39 AM

Yes of course ...
But I want to calulate normals for each vertex...

edotorpedo

Jul 15, 2003 at 6:02 AM

Well, if you''re not required to calculate these normals each frame, here''s what I do (a rectangular grid provided):


CVector n;

n = position[i].getNormal(position[i + numVertices], position[i + 1]);

n.add(position[i].getNormal(position[i + 1], position[i - numVertices]));

n.add(position[i].getNormal(position[i - numVertices], position[i - 1]));

n.add(position[i].getNormal(position[i - 1], position[i + numVertices]));

n.normalize();
n.mirror();

Basically what I''m doing is averaging the normals created by up-right, right-down, down-left, left-up vertices. The getNormal() function returns the normal on position, if it''s connected with its parameter vertices in one triangle.

Edo

Sander

Jul 15, 2003 at 6:03 AM

Calculate all the triangle normals. Then for each vertex, take the average of all the triangle normals that vertex is touching and normalize the result.

Sander Maréchal
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