计算机图形学基础（1）——画线算法

画线算法

• DDA（数值微分法）

void DDALine(int x0,int y0,int x1,int y1){
float delta,x,y,dx,dy;
    dx = x1-x0;
    dy = y1-y0;
    delta = dy/dx;
    y = y0;
    x = x0;
if(delta>=1){   //斜率大于等于1 
for(y=y0;y<=y1;y++){
            DrawPixel(int(x+0.5),y);
            x+=1./delta;
        }
    }
else    for(x=x0;x<=x1;x++){    //斜率小于1 
        DrawPixel(x,int(y+0.5));
        y+=delta;
    }
}

• 中点画线法

 void MidPointLine(int x0,int y0,int x1,int y1){
int a,b,x,y,d,delta1,delta2,k;
    a = y0-y1;
    b = x1-x0;
x = x0;
y = y0;
    k = (y1-y0)>=(x1-x0)?-1:1;
    DrawPixel(x,y);
if(k==1){        //斜率为0~1
        delta1 = 2*a;
        delta2 = 2*(a+b);
        d = 2*a+b;
while(x<x1){
if(d<0){
x++;
y++;
                d+=delta2;
            }
else{
x++;
                d+=delta1;
            }
            DrawPixel(x,y);
        }
    }
else{          //斜率为1~∞
        delta1 = 2*b;
        delta2 = 2*(a+b);
        d = a+2*b;
while(y<y1){
if(d>0){
x++;
y++;
                d+=delta2;
            }
else{
y++;
                d+=delta1;
            }
            DrawPixel(x,y);
        }
    }
} 

• Bersenham画线算法（e=k-0.5）

void BersenhamLine(int x0,int y0,int x1,int y1){
int x,y,dx,dy,e;
x = x0;
y = y0;
    dx = x1-x0;
    dy = y1-y0;
    e = 2*dy - dx;     //new_e = 2*e*dx,此处代码里出现的均为new_e
while(x<x1){
        DrawPixel(x,y);
x++;
        e+=2*dy;
if(e>=1){
y++;
            e-=2*dx;
        }
    }
} 

没有图，有点无聊，附上喜欢的图：

ps3大神绝景版，水墨渲染厉害了