如何修复 openGL 中的位图照明？

Question

我需要有关使用 OpenGL 编写 C++ 代码的帮助 API。我编写了一个程序，可以在屏幕上绘制 4 个 3D 立方体和文本（使用位图）。现在我想添加照明。

我添加了 glMaterial 代码来描述立方体的 material。我不想将 material 属性应用于位图文本。因此，我将 material 的代码放在 绘制立方体之前，我还将绘制立方体的代码和 material 放在 [=11= 之间] 和 popMatrix 对。但是，当我运行代码时，我发现文本改变了颜色。

下面是我正在使用的一些代码：

void init() {
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ligAmb);
glEnable(GL_LIGHTING);
glLightfv(GL_LIGHT0, GL_DIFFUSE, lig[0][0]);
glLightfv(GL_LIGHT0, GL_SPECULAR, lig[0][1]);
glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, ligDir);
glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, exp_one);
glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, cutoff);
glEnable(GL_LIGHT0);
glLightfv(GL_LIGHT1, GL_DIFFUSE, lig[1][0]);
glLightfv(GL_LIGHT1, GL_SPECULAR, lig[1][1]);
glEnable(GL_LIGHT1);
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

}

void drawCube(Point3D colors[], Point3D vertices[]) {
glBegin(GL_QUADS);
glColor3fv(colors[1]);
glVertex3fv(vertices[1]);
glColor3fv(colors[5]);
glVertex3fv(vertices[5]);
glColor3fv(colors[7]);
glVertex3fv(vertices[7]);
glColor3fv(colors[3]);
glVertex3fv(vertices[3]);
glColor3fv(colors[7]);
glVertex3fv(vertices[7]);
glColor3fv(colors[6]);
glVertex3fv(vertices[6]);
glColor3fv(colors[2]);
glVertex3fv(vertices[2]);
glColor3fv(colors[3]);
glVertex3fv(vertices[3]);
glColor3fv(colors[2]);
glVertex3fv(vertices[2]);
glColor3fv(colors[6]);
glVertex3fv(vertices[6]);
glColor3fv(colors[4]);
glVertex3fv(vertices[4]);
glColor3fv(colors[0]);
glVertex3fv(vertices[0]);

glColor3fv(colors[5]);
glVertex3fv(vertices[5]);
glColor3fv(colors[4]);
glVertex3fv(vertices[4]);
glColor3fv(colors[6]);
glVertex3fv(vertices[6]);
glColor3fv(colors[7]);
glVertex3fv(vertices[7]);

glColor3fv(colors[4]);
glVertex3fv(vertices[4]);
glColor3fv(colors[5]);
glVertex3fv(vertices[5]);
glColor3fv(colors[1]);
glVertex3fv(vertices[1]);
glColor3fv(colors[0]);
glVertex3fv(vertices[0]);

glColor3fv(colors[0]);
glVertex3fv(vertices[0]);
glColor3fv(colors[1]);
glVertex3fv(vertices[1]);
glColor3fv(colors[3]);
glVertex3fv(vertices[3]);
glColor3fv(colors[2]);
glVertex3fv(vertices[2]);
glEnd();



}

void displayObject() {

glPushMatrix();
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glLightfv(GL_LIGHT0, GL_POSITION, ligPos[0]);

glLightfv(GL_LIGHT1, GL_POSITION, ligPos[1]);
typedef GLint vertex3[3];

Point3D vertices[8] = { {-1.0, -1.0, -1.0},
                {-1.0, -1.0,  1.0},
                {-1.0,  1.0, -1.0},
                {-1.0,  1.0,  1.0},
                { 1.0, -1.0, -1.0},
                { 1.0, -1.0,  1.0},
                { 1.0,  1.0, -1.0},
                { 1.0,  1.0,  1.0} };

glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_INT, 0, vertices);
GLubyte vertIndex[] = { 6,2,3,7,5,1,0,4,7,3,1,5,4,0,2,6,2,0,1,3,7,5,4,6 
};

glDrawElements(GL_QUADS, 24, GL_UNSIGNED_BYTE, vertIndex);
glPopMatrix();




Point3D colorsb[8] = { {0.,0.,1.},
                    {0.,0.,1.},
                    {0.,0.,1.},
                    {0.,0.,1.},
                    {0.,0.,1.},
                    {0.,0.,1.},
                    {0.,0.,1.},
                    {0.,0.,1.} };

Point3D colorsg[8] = { {0.,1.,0.},
                    {0.,1.,0.},
                    {0.,1.,0.},
                    {0.,1.,0.},
                    {0.,1.,0.},
                    {0.,1.,0.},
                    {0.,1.,0.},
                    {0.,1.,0.} };

Point3D colorsr[8] = { {1.,0.,0.},
                    {1.,0.,0.},
                    {1.,0.,0.},
                    {1.,0.,0.},
                    {1.,0.,0.},
                    {1.,0.,0.},
                    {1.,0.,0.},
                    {1.,0.,0.} };

Point3D colorsy[8] = { {1.,1.,0.},
                    {1.,1.,0.},
                    {1.,1.,0.},
                    {1.,1.,0.},
                    {1.,1.,0.},
                    {1.,1.,0.},
                    {1.,1.,0.},
                    {1.,1.,0.} };



glPushMatrix();

glTranslatef(-0.5f, 4.0f, -6.0f);
glRotatef(10.0, 0.0, 1.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);

glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[0][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[0][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[0][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[0]);

drawCube(colorsb, vertices);
glPopMatrix();

glPushMatrix();
glTranslatef(6.0f, -0.5f, -6.0f);
glRotatef(10.0, 1.0, 0.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);

glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[1][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[1][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[1][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[1]);
drawCube(colorsg, vertices);
glPopMatrix();

glPushMatrix();
glTranslatef(-0.5f, -4.5f, -6.0f);
glRotatef(10.0, 0.0, 1.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);

glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[2][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[2][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[2][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[2]);
drawCube(colorsr, vertices);
glPopMatrix();

glPushMatrix();
glTranslatef(-6.0f, -0.5f, -6.0f);
glRotatef(10.0, 1.0, 0.0, 0.0);
glRotatef(loop, 0.0, 1.0, 0.0);

glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, mat[3][0]);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat[3][1]);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat[3][2]);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shi[3]);
drawCube(colorsy, vertices);
glPopMatrix();
}




void display() {



    displayObject();


    wordColor = "green";
    char str[] = { "Red" };

    glColor3f(0.0, 1.0, 0.0);

    glRasterPos2f(-0.5, 0.0);

    for (int i = 0; i < strlen(str); i++)
    {

        glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, str[i]);
    }

    glPopMatrix();
    loop += 0.05;
    glFlush();
    glutSwapBuffers();

    glutPostRedisplay();

    }

Answer 1

OpenGL 是一个状态机，这意味着它会保持状态，直到您再次明确更改它。因此，当您在绘制一帧期间仅在绘制文本后注意设置照明时，它会在绘制下一帧的文本之前发生。

解决方案是，无论您要绘制什么，您总是在绘制之前设置每个相关状态。对于文本，它就像在绘制文本之前禁用照明一样简单（实际上是在调用 glRasterPos 之前）。

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