球体着色OpenGL

Question

我正在尝试为球体着色。我不知道从哪里开始。我计算了顶点，并使用 GL_TRIANGLE_FAN 将它们连接起来，我还绘制了每个顶点的法线。问题是我什至不知道如何开始做一些阴影/照明。我正在使用 OpeGL 3+。这是我的一些代码：

Sphere的顶点计算（我在网上找到并实现了）：

void CreateUnitSphere(int dtheta,int dphi) //dtheta, dphi angle
{

    GLdouble x,y,z;
    GLdouble magnitude=0;
    int no_vertice=-1;
    int n;
    int k;
    int theta,phi;
    const double PI = 3.1415926535897;
    GLdouble DTOR = (PI/180);//degrees to radians


    //setting the color to white
    for (k=0; k<10296*3; k+=1)
    {
        sphere_vertices[k].color[0] = 1.0f;
        sphere_vertices[k].color[1] = 1.0f;
        sphere_vertices[k].color[2] = 1.0f;
    }


   for (theta=-90;theta<=90-dtheta;theta+=dtheta) {
      for (phi=0;phi<=360-dphi;phi+=dphi) {


     x = cos(theta*DTOR) * cos(phi*DTOR);
     y = cos(theta*DTOR) * sin(phi*DTOR);
         z = sin(theta*DTOR);

    //calculating Vertex 1
    no_vertice+=1;
    sphere_vertices[no_vertice].position[0] = x;
    sphere_vertices[no_vertice].position[1] = y;
    sphere_vertices[no_vertice].position[2] = z;

         x = cos((theta+dtheta)*DTOR) * cos(phi*DTOR);
         y = cos((theta+dtheta)*DTOR) * sin(phi*DTOR);
         z = sin((theta+dtheta)*DTOR);

    //calculating Vertex 2
    no_vertice+=1;
    sphere_vertices[no_vertice].position[0] = x;
    sphere_vertices[no_vertice].position[1] = y;
    sphere_vertices[no_vertice].position[2] = z;

    x = cos((theta+dtheta)*DTOR) * cos((phi+dphi)*DTOR);
        y = cos((theta+dtheta)*DTOR) * sin((phi+dphi)*DTOR);
        z = sin((theta+dtheta)*DTOR);

    //calculating Vertex 3
    no_vertice+=1;
    sphere_vertices[no_vertice].position[0] = x;
    sphere_vertices[no_vertice].position[1] = y;
    sphere_vertices[no_vertice].position[2] = z;

        if (theta > -90 && theta < 90) {

            x = cos(theta*DTOR) * cos((phi+dphi)*DTOR);
            y = cos(theta*DTOR) * sin((phi+dphi)*DTOR);
            z = sin(theta*DTOR);

    //calculating Vertex 4
    no_vertice+=1;
    sphere_vertices[no_vertice].position[0] = x;
    sphere_vertices[no_vertice].position[1] = y;
    sphere_vertices[no_vertice].position[2] = z;

         }

    }

   }

no_vertice = -1;
int no_index=10296; 

//calculate normals and add them to the array of vertices
   for (no_vertice=0; no_vertice<=10296; no_vertice+=1) {

    no_index+=1;

    //getting the sphere's vertices
    x=sphere_vertices[no_vertice].position[0];
    y=sphere_vertices[no_vertice].position[1];
    z=sphere_vertices[no_vertice].position[2];

    //normalising vector "norm(Vertex - Center)"
    magnitude = sqrt((x*x) + (y*y) + (z*z));

    //adding the new vector (the one divided by the magnitude
    sphere_vertices[no_index].position[0] = (x/magnitude)/0.8;
    sphere_vertices[no_index].position[1] = (y/magnitude)/0.8;
    sphere_vertices[no_index].position[2] = (z/magnitude)/0.8;

    ///adding the vertex's normal (line drawing issue)
    no_index+=1;
    sphere_vertices[no_index].position[0] = sphere_vertices[no_vertice].position[0];
    sphere_vertices[no_index].position[1] = sphere_vertices[no_vertice].position[1];
    sphere_vertices[no_index].position[2] = sphere_vertices[no_vertice].position[2];

    }

}

这是我的球体，没有“GL_TRIANGLE_FAN”，只有“GL_LINE_STRIP” 这就是我使用“glDrawArrays”的方式：

glDrawArrays(GL_LINE_STRIP, 0, 10296);
glDrawArrays(GL_LINES, 10297, 30888);

从 0 到 10296 是球体的顶点。 10297-30888 是球体的法线顶点。

这是我的顶点文件：

precision highp float;

in vec3 in_Position; //declare position
in vec3 in_Color;

// mvpmatrix is the result of multiplying the model, view, and projection matrices */
uniform mat4 mvpmatrix;
out vec3 ex_Color;

void main(void) {

// Multiply the mvp matrix by the vertex to obtain our final vertex position (mvp was created in *.cpp)

gl_Position = mvpmatrix * vec4(in_Position, 1.0);

ex_Color = in_Color;

}

和我的片段文件

#version 330
precision highp float;

in vec3 ex_Color;
out vec4 gl_FragColor;

void main(void) {

gl_FragColor = vec4(ex_Color,1.0);

}

现在我知道我需要将法线传递给顶点和片段着色器，但我该怎么做以及如何/在哪里实现光计算，线性插值？ 谢谢

Answer 1

基本上你需要在顶点着色器中计算光照并将顶点颜色传递给片段着色器，如果你想要逐顶点光照，或者将法线和光照方向作为可变变量传递并计算每个像素的所有内容灯光。

这里的主要技巧是，当您将法线传递给片段着色器时，它会在每个片段的顶点之间进行插值，因此着色非常平滑但也较慢。

Here is a very nice article to start with.