Okay, here it is. As a disclaimer, I should say I haven't attempted to make this work efficiently I just want to see it work period. Currently I'm making three passes through all the points to do this which probably can be improved upon, but here's the current sequence of events:
There's a 2D array of lattice points called Lattice that is handling all the physics and then there's a 2D array of vertices, that are used to actually draw the triangles.
1. Loop through all lattice points and set the position of the corresponding vertex to the position of the lattice point.
2. Loop through the vertices and calculate the normal vector for each triangle and add this normal vector to the normal vector each vertex is carrying around. You can see that the loop runs from like 0 to SIZE-1 in both directions, but the triangles are calculated by accessing elements
[j], [i+1][j], [j+1], etc so vertices that are involved in more than one triangle should be getting the contribution from the normal of each triangle they are a part of.
3. Loop through vertices again now that normals are all calculated and draw triangles.
Here's the main DrawLattice() function:
void DrawLattice (void) { for( int i = 0 ; i < LENGTH ; i++ ) { for( int j = 0 ; j < LENGTH ; j++ ) { vertices[j].ClearNormal() ; vertices[j].SetPosition( Lattice[j].position ) ; } } for( i = 0 ; i < LENGTH-1 ; i++ ) { for( int j = 0 ; j < LENGTH-1 ; j++ ) { float face_normal[3] ; // Upper triangle CalculateNormal( vertices[i+1][j].position, vertices[j].position, vertices[i+1][j+1].position, face_normal) ; vertices[i+1][j].normal[0] += face_normal[0] ; vertices[i+1][j].normal[1] += face_normal[1] ; vertices[i+1][j].normal[2] += face_normal[2] ; vertices[j].normal[0] += face_normal[0] ; vertices[j].normal[1] += face_normal[1] ; vertices[j].normal[2] += face_normal[2] ; vertices[i+1][j+1].normal[0] += face_normal[0] ; vertices[i+1][j+1].normal[1] += face_normal[1] ; vertices[i+1][j+1].normal[2] += face_normal[2] ; // Lower triangle CalculateNormal( vertices[j].position, vertices[j+1].position, vertices[i+1][j+1].position, face_normal ) ; vertices[j].normal[0] += face_normal[0] ; vertices[j].normal[1] += face_normal[1] ; vertices[j].normal[2] += face_normal[2] ; vertices[j+1].normal[0] += face_normal[0] ; vertices[j+1].normal[1] += face_normal[1] ; vertices[j+1].normal[2] += face_normal[2] ; vertices[i+1][j+1].normal[0] += face_normal[0] ; vertices[i+1][j+1].normal[1] += face_normal[1] ; vertices[i+1][j+1].normal[2] += face_normal[2] ; } } glBegin(GL_TRIANGLES) ; for( int j = 0 ; j < LENGTH-1 ; j++ ) { for( int i = 0 ; i < LENGTH-1 ; i++ ) { // Upper triangle vertices[i+1][j].Normalize() ; glNormal3fv( vertices[i+1][j].normal ) ; glVertex3fv( vertices[i+1][j].position ) ; vertices[j].Normalize() ; glNormal3fv( vertices[j].normal ) ; glVertex3fv( vertices[j].position ) ; vertices[i+1][j+1].Normalize() ; glNormal3fv( vertices[i+1][j+1].normal ) ; glVertex3fv( vertices[i+1][j+1].position ) ; // Lower triangle vertices[j].Normalize() ; glNormal3fv( vertices[j].normal ) ; glVertex3fv( vertices[j].position ) ; vertices[j+1].Normalize() ; glNormal3fv( vertices[j+1].normal ) ; glVertex3fv( vertices[j+1].position ) ; vertices[i+1][j+1].Normalize() ; glNormal3fv( vertices[i+1][j+1].normal ) ; glVertex3fv( vertices[i+1][j+1].position ) ; } } glEnd() ; }
and the CalculateNormal() function as well:
void CalculateNormal( float *p1, float *p2, float *p3, float *normal ){ float a[3] ; float b[3] ; a[0] = p2[0] - p1[0] ; a[1] = p2[1] - p1[1] ; a[2] = p2[2] - p1[2] ; b[0] = p3[0] - p1[0] ; b[1] = p3[1] - p1[1] ; b[2] = p3[2] - p1[2] ; normal[0] = a[1]*b[2] - a[2]*b[1] ; normal[1] = a[2]*b[0] - a[0]*b[2] ; normal[2] = a[0]*b[1] - a[1]*b[0] ; float length = sqrt( normal[0]*normal[0] + normal[1]*normal[1] + normal[2]*normal[2] ) ; normal[0] /= length ; normal[1] /= length ; normal[2] /= length ;}
I think that should be all the relevant parts, let me know if anything is not clear and thanks to anyone who takes a stab at this.
[Edited by - My_Mind_Is_Going on July 24, 2007 8:09:16 PM]
