如何在屏幕的0,0，-1 opengl座標上繪製黑點？

Question

其實我正在繪製一個立方體，我正在檢查立方體的旋轉問題，但爲此我需要在屏幕的0,0，-1 opengl座標上繪製一個點，我使用透視投影， MyGLSurfaceView和android 1.5 opengl 1.x

如何在屏幕的0,0，-1 opengl座標上繪製黑色或白色點？

Answer 1

如果您希望能夠直接在窗口空間中繪圖，那麼最簡單的方法是使用單位矩陣臨時加載模型視圖和投影，然後用您需要的位置繪製一個GL_POINT。所以這會是這樣的：

glMatrixMode(GL_MODELVIEW); 
glPushMatrix(); 
glLoadIdentity(); 

glMatrixMode(GL_PROJECTION); 
glPushMatrix(); 
glLoadIdentity(); 

// draw the point here; specifics depending on whether you 
// favour VBOs, VBAs, etc 

// e.g. (assuming you don't have any client state enabled 
// on entry and don't care about leaving the vertex array 
// enabled on exit) 
GLfloat vertexLocation[] = {0.0f, 0.0f, -1.0f}; 

glColor4f(0.0f, 0.0f, 0.0f, 1.0f); 
glEnableClientState(GL_VERTEX_ARRAY); 
glVertexPointer(3, GL_FLOAT, 0, vertexLocation); 

glDrawArrays(GL_POINTS, 0, 1); 

// end of example to plot a GL_POINT 

glPopMatrix(); 

glMatrixMode(GL_MODELVIEW); 
glPopMatrix(); 

// and possibly restore yourself to some other matrix mode 
// if, atypically, the rest of your code doesn't assume modelview