Question

I am using GL_TRIANGLE_STRIP to draw my terrain to the screen, however when I compile and run the program I get nothing. When I change GL_TRIANGLE_STRIP to GL_LINES it shows up and works. What can I do to get it working with GL_TRIANGLE_STRIP?

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

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0f, 0.0f, -10.0f);
glRotatef(30.0f, 1.0f, 0.0f, 0.0f);
glRotatef(-_angle, 0.0f, 1.0f, 0.0f);

GLfloat ambientColor[] = {.5, .5, .5, 1.0f};
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);
float scale = 5.0f / max(63.0,63.0);
glScalef(scale, scale*10, scale);
glTranslatef(-(float)(63.0) / 2, 0.0f, -(float)(63.0) / 2);
     /*GLfloat lightColor0[] = {0.6f, 0.6f, 0.6f, 1.0f};
     GLfloat lightPos0[] = {-0.5f, 4, 32, 0.0f};
     glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
     glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);*/



glColor3f(0.3f, 0.9f, 0.0f);
for(int x = 0;x<64;x++){
    glBegin(GL_LINES);
    for(int z = 0;z<63;z++){
        glNormal3f(0,1,0);
        Vertex(x,map[x][z],z);
        Vertex(x,map[x][z+1],z+1);
    }
    glEnd();
}
for(int z = 0;z<64;z++){
    glBegin(GL_LINES);
    for(int x = 0;x<63;x++){
        Vertex(x,map[x][z],z);
        Vertex(x+1,map[x+1][z],z);
    }
    glEnd();
}

I’m not sure this is important but for my terrain I have code that makes it a 3d Gaussian distribution.

Answer 1

An explanation of TRIANGLE_STRIP is found by a Google search. There is an illustration on Wikipedia.

My advice is to print out the first five vertices of your vertex data, and draw it by hand on paper. The fact that GL_LINES work suggest that the right vertices are there, you might just drawing them in the wrong order.

Another piece of advice is to disable backface culling.

glDisable(GL_CULL_FACE);