linux - Debian 和 Win7、Ubuntu 上的 OpenGL 阴影体积差异

Question

在带有最新 opengl 的 windows7 和带有 freeglut3 应用程序的 Ubuntu 12.04 中，我可以使用阴影体积法正确绘制阴影。然而，当我在旧版本的 Debian GNU/Linux 6.0.6 上运行我的代码时，阴影没有被正确绘制，不幸的是我应该绘制这些阴影:(

我认为我有剔除问题，因为当我绘制彩色阴影体积时，我可以正确地看到体积。但是，剔除体积的正面和背面会产生问题，无法绘制阴影。我看不到任何阴影。

这是我的转换阴影代码:

    glDisable(GL_LIGHTING);
    glDepthMask(GL_FALSE);
    glDepthFunc(GL_LEQUAL);

    glEnable(GL_STENCIL_TEST);
    glColorMask(0, 0, 0, 0);
    glStencilFunc(GL_ALWAYS, 1, 0xffffffff);

    // first pass, stencil operation decreases stencil value
    glFrontFace(GL_CCW);
    glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
    for (int i = 0; i < triangles.size(); ++i)
        if (triangles[i]->visible)
            for (int j = 0; j < 3; ++j)
            {
                Triangle *k = triangles[i]->neigh[j];
                if ((k == NULL) || (!k->visible))
                {
                    // here we have an edge, we must draw a polygon
                    p1 = triangles[i]->p[j];
                    p2 = triangles[i]->p[(j+1)%3];

                    //calculate the length of the vector
                    v1.x = (p1.x - wlp[0])*100;
                    v1.y = (p1.y - wlp[1])*100;
                    v1.z = (p1.z - wlp[2])*100;

                    v2.x = (p2.x - wlp[0])*100;
                    v2.y = (p2.y - wlp[1])*100;
                    v2.z = (p2.z - wlp[2])*100;

                    //draw the polygon
                    glBegin(GL_TRIANGLE_STRIP); 
                        glVertex3f(p1.x, p1.y, p1.z);
                        glVertex3f(p1.x + v1.x, p1.y + v1.y, p1.z + v1.z);
                        glVertex3f(p2.x, p2.y, p2.z);
                        glVertex3f(p2.x + v2.x, p2.y + v2.y, p2.z + v2.z);
                    glEnd();
                }
            }

    // second pass, stencil operation increases stencil value
    glFrontFace(GL_CW);
    glStencilOp(GL_KEEP, GL_KEEP, GL_DECR);
    for (int i = 0; i < triangles.size(); ++i)
        if (triangles[i]->visible)
            for (int j = 0; j < 3; ++j)
            {
                Triangle *k = triangles[i]->neigh[j];
                if ((k == NULL) || (!k->visible))
                {
                    // here we have an edge, we must draw a polygon
                    p1 = triangles[i]->p[j];
                    p2 = triangles[i]->p[(j+1)%3];

                    //calculate the length of the vector
                    v1.x = (p1.x - wlp[0])*100;
                    v1.y = (p1.y - wlp[1])*100;
                    v1.z = (p1.z - wlp[2])*100;

                    v2.x = (p2.x - wlp[0])*100;
                    v2.y = (p2.y - wlp[1])*100;
                    v2.z = (p2.z - wlp[2])*100;

                    //draw the polygon
                    glBegin(GL_TRIANGLE_STRIP);
                        glVertex3f(p1.x, p1.y, p1.z);
                        glVertex3f(p1.x + v1.x, p1.y + v1.y, p1.z + v1.z);
                        glVertex3f(p2.x, p2.y, p2.z);
                        glVertex3f(p2.x + v2.x, p2.y + v2.y, p2.z + v2.z);
                    glEnd();
                }
            }

    glFrontFace(GL_CCW);
    glColorMask(1, 1, 1, 1);

    //draw a shadowing rectangle covering the entire screen
    glColor4f(0.0f, 0.0f, 0.0f, 0.4f);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glStencilFunc(GL_NOTEQUAL, 0, 0xffffffff);
    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
    glPushMatrix();
    glLoadIdentity();
    glBegin(GL_TRIANGLE_STRIP);
        glVertex3f(-1, 1,-1);
        glVertex3f(-1,-1,-1);
        glVertex3f( 1, 1,-1);
        glVertex3f( 1,-1,-1);
    glEnd();
    glPopMatrix();
    glDisable(GL_BLEND);

    glDepthFunc(GL_LEQUAL);
    glDepthMask(GL_TRUE);
    glEnable(GL_LIGHTING);
    glDisable(GL_STENCIL_TEST);
    glShadeModel(GL_SMOOTH);
    glPopMatrix();

这是我的初始化:

glEnable(GL_DEPTH_TEST);    // Enable depth Buffering 
glEnable(GL_COLOR_MATERIAL);    // Enable color tracking
glEnable(GL_NORMALIZE); // Enables vector normalization (optional)
glClearColor( 0.4f, 0.4f, 0.8f, 1.0f );     // Set initial value of color buffer (Set background color also)
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);  // Really Nice Perspective Calculations
glDepthFunc(GL_LEQUAL); 

// Lighting initialization
glEnable(GL_TEXTURE_2D);
glShadeModel(GL_SMOOTH);
glEnable(GL_LIGHTING);
glLightfv(GL_LIGHT1, GL_POSITION , light.position); //Set position.
glLightfv(GL_LIGHT1, GL_AMBIENT , light.ambient);   //Set ambient light.
glLightfv(GL_LIGHT1, GL_DIFFUSE , light.diffuse);   //Set diffuse component.
glLightfv(GL_LIGHT1, GL_SPECULAR , light.specular); //Set specular component.
glEnable(GL_LIGHT1);

glMaterialfv(GL_FRONT, GL_AMBIENT, mat.ambient);            // Set Material Ambience
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat.diffuse);            // Set Material Diffuse
glMaterialfv(GL_FRONT, GL_SPECULAR, mat.specular);      // Set Material Specular

glCullFace(GL_BACK);                                // Set Culling Face To Back Face
glEnable(GL_CULL_FACE);                             // Enable Culling
glClearColor(0.1f, 1.0f, 0.5f, 1.0f);               // Set Clear Color (Greenish Color)

// Initialize camera
glMatrixMode(GL_PROJECTION);    // Switch  to projection matrix
glLoadIdentity();   // Clear current matrix to identity matrix
gluPerspective(80, 1 , 0.5 , 1000000);  // Set projection of camera (You can modify the arguments if needed.)

glMatrixMode(GL_MODELVIEW);

Answer 1

确保您传递给 glutInitDisplayMode() 的模式包含 GLUT_STENCIL，否则您可能无法获得模板缓冲区。