glGetUniformLocation为什么返回-1

ibmc490365333 2015-11-01 09:46:38

SDL2+OpenGL ES2编程，Linux4.2.5,mesa11.0.4,Intel集成显卡，gdb调试发现glGetUniformLocation返回-1，窗口黑屏，怎么办？如果直接删掉uniform变量相关的代码就能正常显示三角形,GLSL代码是不是写错了？
我正在学着用OpenGL ES



#include <SDL2/SDL.h>

#include <GLES2/gl2.h>

#include <stdio.h>



void changemvp(GLfloat mvp[16]);



int main(int argc, char **argv){

    SDL_Init(SDL_INIT_VIDEO);



    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);

    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);

    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);

    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);

    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);



    SDL_DisplayMode dm;

    SDL_GetDesktopDisplayMode(0, &dm);



    SDL_Window *win = SDL_CreateWindow("Hello", 0, 0, dm.w, dm.h, SDL_WINDOW_OPENGL);

    SDL_GLContext glc = SDL_GL_CreateContext(win);



    const GLchar * vShaderStr =  

        "attribute vec4 vPosition;"

        "attribute vec4 vColor;"

	"uniform mat4 mvp"

        "varying vec4 v_color;"

        "void main()                 "

        "{                           "

        "    gl_Position = mvp * vPosition;"

        "    v_color = vColor;"

        "}";

    

    const GLchar * fShaderStr =  

        "precision mediump float;"

        "varying vec4 v_color;"

        "void main()"

        "{"

        "  gl_FragColor = v_color;"

        "}";



    GLuint vertexShader;

    GLuint fragmentShader;

    GLuint programObject;



    vertexShader = glCreateShader(GL_VERTEX_SHADER);

    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);



    glShaderSource(vertexShader, 1, &vShaderStr, NULL);

    glShaderSource(fragmentShader, 1, &fShaderStr, NULL);

    glCompileShader(vertexShader);

    glCompileShader(fragmentShader);



    programObject = glCreateProgram ( );



    glAttachShader ( programObject, vertexShader );

    glAttachShader ( programObject, fragmentShader );



    glLinkProgram ( programObject );

    glDeleteShader(vertexShader);

    glDeleteShader(fragmentShader);



    glUseProgram(programObject);



    glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );

    glClear(GL_COLOR_BUFFER_BIT);

    glViewport(0,0,dm.w,dm.h);





    GLfloat vVertices[] = {  0.0f,  0.5f, 0.0f, 0.67f, 0.4f, 0.47f,

                             -1.0f, -0.5f, 0.0f, 1.0f, 0.4f, 0.97f,

                             0.5f, -0.5f, 0.0f, 0.0f, 0.4f, 0.57f

    };

    #define stride 6

    #define vPosition_offset 0

    #define vPosition_size 3

    #define vColor_offset 3

    #define vPosition_size 3



    GLfloat mvp[16]={1,0,0,0,

		     0,1,0,0,

		     0,0,1,0,

		     0,0,0,1

		    };

    glBindAttribLocation ( programObject, 0, "vPosition" );

    glBindAttribLocation ( programObject, 1, "vColor" );

    glVertexAttribPointer ( 0, vPosition_size, GL_FLOAT, GL_FALSE, stride*sizeof(float), vVertices+vPosition_offset );

    glVertexAttribPointer ( 1, vPosition_size, GL_FLOAT, GL_FALSE, stride*sizeof(float), vVertices+vColor_offset );

    int mvploc = glGetUniformLocation(programObject, "mvp");

    glUniformMatrix4fv(mvploc, 1, GL_FALSE, mvp);

    glEnableVertexAttribArray ( 0 );

    glEnableVertexAttribArray ( 1 );

    glDrawArrays(GL_TRIANGLES, 0, 3);

    SDL_GL_SwapWindow(win);





    SDL_Event e;

    while(1){

        int r = SDL_PollEvent(&e);

        if(!r)continue;

        if(e.type == SDL_KEYDOWN)goto quit;

	if(e.type == SDL_MOUSEMOTION){

		changemvp(mvp);

	}

    }



    quit:

    SDL_GL_DeleteContext(glc);

    SDL_DestroyWindow(win);

    SDL_Quit();

}



void changemvp(GLfloat mvp[16]){

}