如何在OpenGL ES應用程序中指定立方體的每面顏色？

Question

我在下面的代碼中定義了一個立方體。我想每個6個面像的指定顏色：

前臉：COLOR1

背面：COLOR2

左臉：COLOR3

右臉：color4

頂部face：color5

底面：color6

請注意，在OpenGL ES中，我們只有三角形而不是四邊形。我正在尋找解決我的問題的工作示例代碼，因爲工作示例代碼的價值超過千言萬語，就像他們對圖片所說的那樣。

這裏是立方體：

float vertices[] = { -width, -height, -depth, // 0 
           width, -height, -depth, // 1 
           width, height, -depth, // 2 

          -width, height, -depth, // 3 

          -width, -height, depth, // 4 


           width, -height, depth, // 5 

           width, height, depth, // 6 

          -width, height, depth // 7 
     }; 
    short indices[] = { 0, 2, 1, 
       0, 3, 2, 

       1,2,6, 
       6,5,1, 

       4,5,6, 
       6,7,4, 

       2,3,6, 
       6,3,7, 

       0,7,3, 
       0,4,7, 

       0,1,5, 
       0,5,4 
         }; 

這是繪圖代碼：

gl.glFrontFace(GL10.GL_CCW); 
     // Enable face culling. 
     gl.glEnable(GL10.GL_CULL_FACE); 
     // What faces to remove with the face culling. 
     gl.glCullFace(GL10.GL_BACK); 
     // Enabled the vertices buffer for writing and to be used during 
     // rendering. 
     gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); 

     // Specifies the location and data format of an array of vertex 
     // coordinates to use when rendering. 
     gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVerticesBuffer); 


      // Bind the texture according to the set texture filter 
      gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[filter]); 
      gl.glEnable(GL10.GL_TEXTURE_2D); 


     if (mColorBuffer != null) { 
      // Enable the color array buffer to be used during rendering. 
      gl.glEnableClientState(GL10.GL_COLOR_ARRAY); 
      gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer); 
     } 



     gl.glDrawElements(GL10.GL_TRIANGLES, mNumOfIndices, 
       GL10.GL_UNSIGNED_SHORT, mIndicesBuffer); 

     // ALL the DRAWING IS DONE NOW 

     // Disable the vertices buffer. 
     gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); 


      gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); 


     // Disable face culling. 
     gl.glDisable(GL10.GL_CULL_FACE); 

Answer 1

這是桌面GLUT代碼，但核心的邏輯應當直接轉化爲OpenGL ES的：

#include <GL/glut.h> 
#include <cstdlib> 

void glutTexturedCube(GLdouble size) 
{ 
    GLfloat color1[] = { 255, 0, 0 }; 
    GLfloat color2[] = { 0, 255, 0 }; 
    GLfloat color3[] = { 0, 0, 255 }; 
    GLfloat color4[] = { 255, 255, 0 }; 
    GLfloat color5[] = { 0, 255, 255 }; 
    GLfloat color6[] = { 255, 255, 255 }; 

    GLfloat color[] = { 
     color1[0], color1[1], color1[2], 
     color1[0], color1[1], color1[2], 
     color1[0], color1[1], color1[2], 
     color1[0], color1[1], color1[2], 
     color1[0], color1[1], color1[2], 
     color1[0], color1[1], color1[2], 

     color2[0], color2[1], color2[2], 
     color2[0], color2[1], color2[2], 
     color2[0], color2[1], color2[2], 
     color2[0], color2[1], color2[2], 
     color2[0], color2[1], color2[2], 
     color2[0], color2[1], color2[2], 

     color3[0], color3[1], color3[2], 
     color3[0], color3[1], color3[2], 
     color3[0], color3[1], color3[2], 
     color3[0], color3[1], color3[2], 
     color3[0], color3[1], color3[2], 
     color3[0], color3[1], color3[2], 

     color4[0], color4[1], color4[2], 
     color4[0], color4[1], color4[2], 
     color4[0], color4[1], color4[2], 
     color4[0], color4[1], color4[2], 
     color4[0], color4[1], color4[2], 
     color4[0], color4[1], color4[2], 

     color5[0], color5[1], color5[2], 
     color5[0], color5[1], color5[2], 
     color5[0], color5[1], color5[2], 
     color5[0], color5[1], color5[2], 
     color5[0], color5[1], color5[2], 
     color5[0], color5[1], color5[2], 

     color6[0], color6[1], color6[2], 
     color6[0], color6[1], color6[2], 
     color6[0], color6[1], color6[2], 
     color6[0], color6[1], color6[2], 
     color6[0], color6[1], color6[2], 
     color6[0], color6[1], color6[2], 
    }; 

    GLfloat vert[] = { 
     // top (+z) 
     -1, -1, 1, 
     1, -1, 1, 
     -1, 1, 1, 
     -1, 1, 1, 
     1, -1, 1, 
     1, 1, 1, 

     // bottom (-z) 
     -1, -1, -1, 
     -1, 1, -1, 
     1, -1, -1, 
     1, -1, -1, 
     -1, 1, -1, 
     1, 1, -1, 

     // right (+x) 
     1, -1, -1, 
     1, 1, -1, 
     1, -1, 1, 
     1, -1, 1, 
     1, 1, -1, 
     1, 1, 1, 

     // left (-x) 
     -1, -1, -1, 
     -1, -1, 1, 
     -1, 1, -1, 
     -1, 1, -1, 
     -1, -1, 1, 
     -1, 1, 1, 

     // front (+y) 
     -1, -1, -1, 
     1, -1, -1, 
     -1, -1, 1, 
     -1, -1, 1, 
     1, -1, -1, 
     1, -1, 1, 

     // back (-y) 
     -1, 1, -1, 
     -1, 1, 1, 
     1, 1, -1, 
     1, 1, -1, 
     -1, 1, 1, 
     1, 1, 1, 
    }; 

    GLushort idxs[] = { 
     0, 1, 2, 
     3, 4, 5, 

     6, 7, 8, 
     9,10,11, 

     12,13,14, 
     15,16,17, 

     18,19,20, 
     21,22,23, 

     24,25,26, 
     27,28,29, 

     30,31,32, 
     33,34,35 
    }; 

    glEnableClientState(GL_COLOR_ARRAY); 
    glEnableClientState(GL_VERTEX_ARRAY); 
    glColorPointer(3, GL_FLOAT, 0, color); 
    glVertexPointer(3, GL_FLOAT, 0, vert); 

    glPushMatrix(); 
    glColor4f(1, 1, 1, 1); 
    glScaled(size, size, size); 
    glDrawElements(GL_TRIANGLES, sizeof(idxs)/sizeof(idxs[0]), GL_UNSIGNED_SHORT, idxs); 
    glPopMatrix(); 

    glDisableClientState(GL_COLOR_ARRAY); 
    glDisableClientState(GL_VERTEX_ARRAY); 
} 

static GLuint texName; 

void init(void) 
{ 
    glClearColor(0,0,0,0); 

    glEnable(GL_DEPTH_TEST); 
    glShadeModel(GL_SMOOTH); 
    glEnable(GL_CULL_FACE); 
} 

void display(void) 
{ 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 

    // projection 
    glMatrixMode(GL_PROJECTION); glLoadIdentity(); 
    int viewport[4]; glGetIntegerv(GL_VIEWPORT, viewport); 
    gluPerspective(60.0, (GLdouble)viewport[2]/(GLdouble)viewport[3], 1.0, 100.0); 

    // view transform 
    glMatrixMode(GL_MODELVIEW); glLoadIdentity(); 
    glTranslatef(0,0,-4); 

    // render 
    glPushMatrix(); 
    const float ANGLE_SPEED = 30; // degrees/sec 
    float angle = ANGLE_SPEED * (glutGet(GLUT_ELAPSED_TIME)/1000.0f); 
    glRotatef(angle*0.5f, 1, 0, 0); 
    glRotatef(angle, 0, 1, 0); 
    glRotatef(angle*0.7f, 0, 0, 1); 

    glutTexturedCube(1); 

    glutSwapBuffers(); 
} 

void reshape(int w, int h) 
{ 
    glViewport(0, 0, (GLsizei) w, (GLsizei) h); 
} 

void keyboard (unsigned char key, int x, int y) 
{ 
    switch (key) 
     { 
     case 27: exit(0); break; 
     default: break; 
     } 
} 

void idle() 
{ 
    glutPostRedisplay(); 
} 

int main(int argc, char** argv) 
{ 
    glutInit(&argc, argv); 
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH); 
    glutInitWindowSize(640, 480); 
    glutInitWindowPosition(100, 100); 
    glutCreateWindow (argv[0]); 
    glutDisplayFunc(display); 
    glutReshapeFunc(reshape); 
    glutKeyboardFunc(keyboard); 
    glutIdleFunc(idle); 

    init(); 
    glutMainLoop(); 
    return 0; 
}