在C ++中构建UV Sphere

Question

I'm trying to make a UV sphere in C++ using Qt Creator, I want to build the sphere without using the openGL commands. I'm trying trying to add the vertices to lObject and then add the normals and triangles. The sphere will have a radius of 1. First problem is that it doesn't render a sphere when drawn, so maybe I'm not adding the right vertices or maybe I'm not adding the triangles correctly. Any help on what I'm doing wrong would be great.

Here's what I've tried:

NodeObject* ObjectFactory::buildSphere(int slices, int stacks)
{ 
    // Allocate a new node object
    NodeObject* lObject = new NodeObject();

    for(int i=0; i<stacks; i++)
    {
        double lnum1 = 360.0/stacks;
        double lTheta = ((double)i)*(lnum1*(M_PI/180.0));       
        double lNextTheta = ((double)(i+1))*lnum1*(M_PI/180.0);    

        for(int j=0; j<slices; j++)
        {
            double lnum2 = 180.0/slices;
            double lPhi = ((double)i)*(lnum2*(M_PI/180.0));     
            double lNextPhi = ((double)(i+1))*lnum1*(M_PI/180.0);

            lObject->addVertex(0.0, 1.0, 0.0); //Top

            lObject->addVertex(sin(lTheta)*cos(lPhi), sin(lTheta)*sin(lPhi), cos(lTheta));
            lObject->addVertex(sin(lNextTheta)*cos(lNextPhi), sin(lNextTheta)*sin(lNextPhi),    cos(lNextTheta));

            lObject->addVertex(sin(lTheta)*cos(lPhi), -(sin(lTheta)*sin(lPhi)), cos(lTheta));
            lObject->addVertex(sin(lNextTheta)*cos(lNextPhi), -(sin(lNextTheta)*sin(lNextPhi)),              cos(lNextTheta));

            lObject->addVertex(0.0, -1.0, 0.0); //Bottom

            lObject->addNormal(0.0,1.0,0.0);
            lObject->addNormal(0.0,-1.0,0.0);
            lObject->addNormal(sin(lTheta)*cos(lPhi),sin(lTheta)*sin(lPhi), cos(lTheta));

            for(int k=0; k<pSlices*6; k++)
            {
                if(i==0) { lObject->addTriangle(0,1,2,0,0,0); }
                else if(i+1 == stacks) {lObject->addTriangle(2,0,1,0,0,0); }
                else
                {
                    lObject->addTriangle(k, k+1, k+2,k,k+1,k+2);
                }
            }
        }

    }
    return lObject;
}

Answer 1

In you third for loop what is the value for pSlices? Also why are you adding top and bottom for each stack?

And for better practice generate the vertices first, then do other stuff.

You can use a simple data structure for holding the data such as, also generate one layer of vertices at the inner loop.:

QVector3D sphereVertices[stacks][slices];

For first layer fill it with (0.0, 1.0, 0.0); For last layer fill it with (0.0, -1.0, 0.0);

Then iterate over the vertices to calculate normals and create triangles in CCW.

for ( int i = 0; i < stacks -1; i++){ //-1 is due to we are using the next stack to create the face
    for ( int j = 0; j < slices -1; j++){ //we are also using the next slice
        //Add these vertex indices
        //First triangle indices
        //i*slices + j, (i+1)*slices + j, (i+1)*slices + j + 1
        //Second triangle indices
        //i*slices + j, (i+1)*slices + j + 1, i*slices + j + 1
        //Furthermore you can calculate triangle normal by using these vertices
        //https://www.opengl.org/wiki/Calculating_a_Surface_Normal
    }
}