顶点着色器中的Phong照明

我正在尝试使用适用于Android的OpenGL ES 2.0来显示具有法线和颜色的简单多维数据集。为此，我创建了一个着色器程序，附加了我的顶点和片段着色器，并链接了我的程序，如下所示：

// Create empty OpenGL ES Program
mProgram = GLES20.glCreateProgram();
MyGLRenderer.checkGlError("glCreateProgram");

// Add the vertex shader to program
vertexShaderCode = Utilities.convertResourceToString(context, R.raw.vert_shader_hw3);
int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
GLES20.glAttachShader(mProgram, vertexShader);
MyGLRenderer.checkGlError("glAttachShader");

// Add the fragment shader to program
fragmentShaderCode = Utilities.convertResourceToString(context, R.raw.frag_shader_hw3);
int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
GLES20.glAttachShader(mProgram, fragmentShader);
MyGLRenderer.checkGlError("glAttachShader");

// Bind attributes
GLES20.glBindAttribLocation(mProgram, 0, "aPosition");
MyGLRenderer.checkGlError("glBindAttribLocation");

GLES20.glBindAttribLocation(mProgram, 1, "aNormal");
MyGLRenderer.checkGlError("glBindAttribLocation");

GLES20.glBindAttribLocation(mProgram, 2, "aColor");
MyGLRenderer.checkGlError("glBindAttribLocation");

// Create OpenGL program executables
GLES20.glLinkProgram(mProgram);
MyGLRenderer.checkGlError("glLinkProgram");

// Add program to OpenGL ES environment
GLES20.glUseProgram(mProgram);
MyGLRenderer.checkGlError("glUseProgram");

然后它立即崩溃，打印到LogCat：glUseProgram: glError 1281我检查了文档，然后找到glError 1281，即GL_INVALID_VALUE，如果program既不是0也不是OpenGL生成的值，则会生成该错误。

谷歌搜索了大约10个小时之后，我决定转向StackOverflow寻求帮助。知道让我的顶点着色器代码使glUseProgram表现为这种方式可能有什么问题吗？

这是我的顶点着色器代码，我尝试实现phong照明：

uniform mat4 uMVPMatrix;
uniform mat4 uMVMatrix;
uniform vec3 uLightPosition;
uniform vec4 uAmbient;
uniform vec4 uDiffuse;
uniform vec4 uSpecular;
uniform vec4 uEmission;
uniform float uShininess;

attribute vec4 aPosition;
attribute vec3 aNormal;
attribute vec4 aColor;

varying vec4 vColor;

vec4 phong()
{
    //  P is the vertex coordinate on body
    vec3 P = vec3(uMVMatrix * aPosition);

    //  N is the object normal at P
    vec3 N = vec3(uMVMatrix * vec4(aNormal, 0.0)); 

    //  Light Position for light 0
    vec3 LightPos = uLightPosition;

    //  L is the light vector
    vec3 L = normalize(LightPos - P);

    //  R is the reflected light vector R = 2(L.N)N - L
    vec3 R = reflect(-L, N);

    //  V is the view vector (eye at the origin)
    vec3 V = normalize(-P);

    //  Diffuse light intensity is cosine of light and normal vectors
    float Id = max(dot(L,N) , 0.0);

    //  Shininess intensity is cosine of light and reflection vectors to a power
    float Is = (Id>0.0) ? pow(max(dot(R,V) , 0.0) , uShininess) : 0.0;

    //  Vertex color
    return uEmission + uAmbient + Id*uDiffuse + Is*uSpecular;
}

void main()
{
    gl_Position = uMVPMatrix * aPosition;
    vColor = phong() * 0.5*(gl_Position/gl_Position.w + 1.0);
}