OpenGL放大效率

我是OpenGL的初學者，也是我的第一個應用程序，我嘗試使用三角形的重心細分方法生成分形。我不知道OpenGL的透視變化功能，我的第一個想法是縮放和改變視點算法，每次按下一個按鍵時，只需重新繪製具有不同起點座標和縮放因子的整個分形（相機移動箭頭和+/- - 用於縮放）。假設對於重心細分的6次迭代繪製約56000個三角形（6^0 + 6^1 + 6^2 + 6^3 + 6^4 + 6^5 + 6^6個三角形）這個算法效率很低。所以我試圖用gluPerspective（）進行縮放，結果令人傷心的是黑屏，而不是分形。我有兩個主要問題：OpenGL放大效率

不OpenGL函數的角度變化和觀點（gluPerspective（），gluLookAt（），glFrustum（）等）重繪使用不同的座標整個數字，或使用獲得的更有效的方法相同的結果？在我的情況下，他們的使用會更有效率嗎？

我在代碼中做了什麼錯誤。爲什麼我會變黑屏？

#include <GL/glfw.h> 
#include <iostream> 
#include <math.h> 

using namespace std; 

struct punct{ GLdouble x, y;}; //"punct" means "point" in my native language 
punct A, B, C; 
int n=0, mode=1; 
double l=1.6, ox=0, oy=0, scale=1; 

punct mid (punct A, punct B); 
void initiate(); 
void line (punct A, punct B); 
void triangle (punct A, punct B, punct C); 
void divide (punct A, punct B, punct C,int i); 

int main() 
{ 
    int  width, height; 
    bool running = true; 
    char input=NULL; 

    glfwInit(); 

    if(!glfwOpenWindow(800, 800, 0, 0, 0, 0, 0, 0, GLFW_FULLSCREEN)) 
    { 
     glfwTerminate(); 
     return 0; 
    } 

    glfwSetWindowTitle("Baricentric"); 

    while(running) 
    { 
     glfwGetWindowSize(&width, &height); 
     height = height > 0 ? height : 1; 

     glViewport(0, 0, width, height); 

     glClearColor(0.0f, 0.0f, 0.0f, 0.0f); 
     glClear(GL_COLOR_BUFFER_BIT); 

     //This functions make my screen black 
     //glMatrixMode(GL_MODELVIEW); 
     //glLoadIdentity(); 
     //gluPerspective (50*scale, width/height, 10.0, 100.0); 

     initiate(); 

     if(glfwGetKey(GLFW_KEY_KP_ADD) && glfwGetKey(GLFW_KEY_LCTRL)) input='+'; 
     if(!glfwGetKey(GLFW_KEY_KP_ADD) && input=='+') { 
     if(n<7) n++; 
     input='\n'; 
     } 
     if(glfwGetKey(GLFW_KEY_KP_SUBTRACT) && glfwGetKey(GLFW_KEY_LCTRL)) input='-'; 
     if(!glfwGetKey(GLFW_KEY_KP_SUBTRACT) && input=='-') { 
      if(n>0)n--; 
      input='\n'; 
     } 

     if(glfwGetKey(GLFW_KEY_KP_1)||glfwGetKey('1')) input='1'; 
     if(!glfwGetKey(GLFW_KEY_KP_1) && input=='1') { 
      mode=1; 
      input='\n'; 
     } 

     if(glfwGetKey(GLFW_KEY_KP_0)||glfwGetKey('0')) input='0'; 
     if(!glfwGetKey(GLFW_KEY_KP_0) && input=='0') { 
      mode=0; 
      input='\n'; 
     } 

     if(glfwGetKey(GLFW_KEY_KP_ADD) && !glfwGetKey(GLFW_KEY_LCTRL)) l+=0.002*(n+0.5); //'l' is replaced with 'scale' when using gluPerspective() 
     if(glfwGetKey(GLFW_KEY_KP_SUBTRACT) && !glfwGetKey(GLFW_KEY_LCTRL)) l-=0.002*(n+0.5); //'l' is replaced with 'scale' when using gluPerspective() 
     if(glfwGetKey(GLFW_KEY_UP)) oy-=0.002*(n+0.5); 
     if(glfwGetKey(GLFW_KEY_DOWN)) oy+=0.002*(n+0.5); 
     if(glfwGetKey(GLFW_KEY_RIGHT)) ox+=0.002*(n+0.5); 
     if(glfwGetKey(GLFW_KEY_LEFT)) ox-=0.002*(n+0.5); 


     if (n) divide (A,B,C,1); 


     glfwSwapBuffers(); 

     running = !glfwGetKey(GLFW_KEY_ESC) && glfwGetWindowParam(GLFW_OPENED); 
    } 

    glfwTerminate(); 

    return 0; 
} 

punct mid (punct A, punct B) { 
    punct C; 
    C.x=(A.x+B.x)/2; 
    C.y=(A.y+B.y)/2; 
    return C; 
} 

void initiate() { 

    A.x = -(l/2)+ox; A.y = -(l*sqrt(3)/4)+oy; 
    B.x = l/2+ox; B.y = A.y; 
    C.x = 0+ox; C.y = (l*sqrt(3)/4)+oy; 

    glBegin (GL_QUADS); 
     glColor3f(0.93,0.84,0.82); glVertex3d(-1, 1, 0); 
     glColor3f(0.01,0.95,0.83); glVertex3d(-1, -1, 0); 
     glColor3f(0.80,0.71,0.80); glVertex3d(1, -1, 0); 
     glColor3f(0.8,1,0.8); glVertex3d(1, 1, 0); 
    glEnd(); 

    glBegin (GL_TRIANGLES); 
     glColor3f(0,0.6,0.88); glVertex3d(C.x, C.y, 0); 
     glColor3f(0,0.77,0.73); glVertex3d(B.x, B.y, 0); 
     glColor3f(0.01,0.66,0.62); glVertex3d(A.x, A.y, 0); 
    glEnd(); 

    if (mode==0) { 
     glLineWidth (0.1); 
     glColor3f(0,0,0.36); 
     glBegin (GL_LINE_LOOP); 
      glVertex3d(C.x, C.y, 0); 
      glVertex3d(B.x, B.y, 0); 
      glVertex3d(A.x, A.y, 0); 
     glEnd(); 
    } 
} 


void divide (punct A, punct B, punct C, int i) { 
    if(i<=n) { 
     punct a, b, c, G; 
     c=mid(A,B); 
     b=mid(A,C); 
     a=mid(B,C); 
     G.x=(A.x+B.x+C.x)/3; 
     G.y=(A.y+B.y+C.y)/3; 
     if(mode==1) { 
      triangle(G,a,C); 
      triangle(G,b,C); 
      triangle(G,a,B); 
      triangle(G,c,B); 
      triangle(G,c,A); 
      triangle(G,b,A); 
     } 
     line(c,C); 
     line(a,A); 
     line(b,B); 
     divide(G,a,C,i+1); 
     divide(G,b,C,i+1); 
     divide(G,a,B,i+1); 
     divide(G,c,B,i+1); 
     divide(G,c,A,i+1); 
     divide(G,b,A,i+1); 
    } 

} 

void line (punct A, punct B) { 
    glBegin (GL_LINE_STRIP); 
     glVertex3d(A.x,A.y,0); 
     glVertex3d(B.x,B.y,0); 
    glEnd(); 
} 

void triangle (punct A, punct B, punct C) { 
    glBegin (GL_TRIANGLES); 
     glColor3f(0,0.6,0.88); glVertex3d(C.x, C.y, 0); 
     glColor3f(0,0.77,0.73); glVertex3d(B.x, B.y, 0); 
     glColor3f(0.01,0.66,0.62); glVertex3d(A.x, A.y, 0); 
    glEnd(); 
}

來源

2013-05-30 Ioan Dinu

像許多之前，你已經愛上了思維的OpenGL的誤解是一個場景圖。不是這種情況。

OpenGL是一個繪圖API。您的操作系統提供畫布（窗口，PBuffer，Pixmap等），OpenGL以點，線或三角形的形式提供繪圖工具。

不OpenGL的角度變化和觀點功能（gluPerspective（），gluLookAt（），glFrustum（）等）重繪使用不同的座標整個身影，

他們所要做的就是改變值幾個矩陣。屏幕上的任何內容都不會因此而改變。你必須重新繪製整個事物才能做出明顯的改變。

來源

2013-05-30 20:35:03 datenwolf

OpenGL放大效率

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