could anyone please help me calculating vertex normals in OpenGL? I am loading an obj file and adding Gouraud shading by calculating vertex normals without using glNormal3f or glLight functions.. I have declared functions like operators, crossproduct, innerproduct,and etc.. I have understood that in order to get vertex normals, I first need to calculate surface normal aka normal vector with crossproduct.. and also since I am loading an obj file.. and I am placing the three points of Faces of the obj file in id1,id2,id3 something like that
I would be grateful if anyone can help me writing codes or give me a guideline how to start the codes. please ... thanks..
its to draw
FACE cur_face = cube.face[i];
glColor3f(cube.vertex_color[cur_face.id1].x,cube.vertex_color[cur_face.id1].y,cube.vertex_color[cur_face.id1].z);
glVertex3f(cube.vertex[cur_face.id1].x,cube.vertex[cur_face.id1].y,cube.vertex[cur_face.id1].z);
glColor3f(cube.vertex_color[cur_face.id2].x,cube.vertex_color[cur_face.id2].y,cube.vertex_color[cur_face.id2].z);
glVertex3f(cube.vertex[cur_face.id2].x,cube.vertex[cur_face.id2].y,cube.vertex[cur_face.id2].z);
glColor3f(cube.vertex_color[cur_face.id3].x,cube.vertex_color[cur_face.id3].y,cube.vertex_color[cur_face.id3].z);
glVertex3f(cube.vertex[cur_face.id3].x,cube.vertex[cur_face.id3].y,cube.vertex[cur_face.id3].z);
}
This is the equation for color calculation
VECTOR kd;
VECTOR ks;
kd=VECTOR(0.8, 0.8, 0.8);
ks=VECTOR(1.0, 0.0, 0.0);
double inner = kd.InnerProduct(ks);
int i, j;
for(i=0;i<cube.vertex.size();i++)
{
VECTOR n = cube.vertex_normal[i];
VECTOR l = VECTOR(100,100,0) - cube.vertex[i];
VECTOR v = VECTOR(0,0,1) - cube.vertex[i];
float xl = n.InnerProduct(l)/n.Magnitude();
VECTOR x = (n * (1.0/ n.Magnitude())) * xl;
VECTOR r = x - (l-x);
VECTOR color = kd * (n.InnerProduct(l)) + ks * pow((v.InnerProduct(r)),10);
cube.vertex_color[i] = color;