[ntustgraphics99] [電腦圖學]嗨，大家好，有鑑於大家保證,一定,硬要,需要一個討論平台
- From: 天亮damody <t1238142000@xxxxxxxxx>
- To: ntustgraphics99@xxxxxxxxxxxxx
- Date: Mon, 15 Nov 2010 16:29:52 +0800
2010/11/15 天亮damody <t1238142000@xxxxxxxxx>
> 各位同學大家好：
> 助教我"黃亮軒"申請了一個maillist來跟大家討論，
> 所謂的maillist就是你寄給ntustgraphics99@xxxxxxxxxxxxx的信，助教能看到，大家也能看到，
> 我回的信大家也都能收到，這樣就比較不會有重複的問題一直問，別人問助教得到的結果，其它人不知道等問題，
> 希望大家多多利用這個資源多多討論^^
> 最後給大家一點參考如何切點跟看正面
> Frustum.h是給大家一點參考
> 決定視野內的點最好還是用投影片上的ccw比較準。
>
> 下面是簡單用視野去切點，但沒有寫怎麼找到要畫的邊切好的兩點。
> void Maze::
> Draw_View(const float focal_dist)
> //======================================================================
> {
> using namespace std;
> frame_num++;
> LineSeg line(view_cell->edges[0]);
> cout << line.start[0] << " " << line.start[1] << " " << line.end[0] <<
> " " << line.end[1] << endl;
> point clip1, clip2;
> Frustum viewf(viewer_dir, viewer_fov, viewer_posn[X], viewer_posn[Y]);
> clip1 = line.Cross_Param_point(viewf.edgelines[0]); //clip1 左邊切到的點
> float bill = viewf.edgelines[0].Cross_Param(line);
> float bill2 = viewf.edgelines[1].Cross_Param(line);
> clip2 = line.Cross_Param_point(viewf.edgelines[1]); //clip2 右邊切到的點
> if (bill>0 && bill<1 || bill2>0 && bill2<1)
> cout << clip1.x << " " << clip1.y << " " << clip2.x << " " <<
> clip2.y << endl;
> else
> cout << "error : " << bill << " " << bill2 << endl;
> }
>
>
> --
> 有心情就是有壓力^^
>
--
有心情就是有壓力^^
#pragma once
#include "LineSeg.h"
#include <cmath>
static double rad(double num) { return num / 180.0 * 3.14159; };
static double deg(double num) { return num * 180.0 / 3.14159; };
static float rad(float num) { return (float)(num / 180.0 * 3.14159); };
static float deg(float num) { return (float)(num * 180.0 / 3.14159); };
class Frustum {
public:
LineSeg edgelines[2];
Frustum(float viewangle, float fov, float pos_x, float pos_y)
{
edgelines[0] = LineSeg(pos_x, pos_y, pos_x + 1*cos(
rad(viewangle - fov/2) ), pos_y + 1*sin( rad(viewangle - fov/2) ));
edgelines[0].end[0] +=
(edgelines[0].end[0]-edgelines[0].start[0])*100;
edgelines[0].end[1] +=
(edgelines[0].end[1]-edgelines[0].start[1])*100;
edgelines[1] = LineSeg(pos_x, pos_y, pos_x + 1*cos(
rad(viewangle + fov/2) ), pos_y + 1*sin( rad(viewangle + fov/2) ));
edgelines[1].end[0] +=
(edgelines[1].end[0]-edgelines[1].start[0])*100;
edgelines[1].end[1] +=
(edgelines[1].end[1]-edgelines[1].start[1])*100;
}
Frustum(float start_x, float start_y, float right_end_x, float
right_end_y, float left_end_x, float left_end_y)
{
edgelines[0] = LineSeg(
start_x,start_y,right_end_x,right_end_y);
edgelines[0].end[0] +=
(edgelines[0].end[0]-edgelines[0].start[0])*100;
edgelines[0].end[1] +=
(edgelines[0].end[1]-edgelines[0].start[1])*100;
edgelines[1] = LineSeg( start_x,start_y,left_end_x,left_end_y);
edgelines[1].end[0] +=
(edgelines[1].end[0]-edgelines[1].start[0])*100;
edgelines[1].end[1] +=
(edgelines[1].end[1]-edgelines[1].start[1])*100;
}
};/************************************************************************
File: LineSeg.cpp
Author:
Stephen Chenney, schenney@xxxxxxxxxxx
Modifier
Yu-Chi Lai, yu-chi@xxxxxxxxxxx
Comment:
(c) 2001-2002 Stephen Chenney,
University of Wisconsin at Madison
Class header file for LineSeg
class.
Platform: Visio Studio.Net 2003 (converted to 2005)
*************************************************************************/
#include "LineSeg.h"
//**********************************************************************
//
// * Constructor from an edge
//======================================================================
LineSeg::
LineSeg(Edge *e)
//======================================================================
{
start[0] = e->endpoints[Edge::START]->posn[Vertex::X];
start[1] = e->endpoints[Edge::START]->posn[Vertex::Y];
end[0] = e->endpoints[Edge::END]->posn[Vertex::X];
end[1] = e->endpoints[Edge::END]->posn[Vertex::Y];
}
//**********************************************************************
//
// * Constructor for specifyng start and end point
//======================================================================
LineSeg::
LineSeg(float xs, float ys, float xe, float ye)
//======================================================================
{
start[0] = xs;
start[1] = ys;
end[0] = xe;
end[1] = ye;
}
//**********************************************************************
//
// * Return the parameter value at which this segment crosses the given
// segment. This will return parameter values outside the range 0,1
// THIS FUNCTION IS EXTREMELY USEFUL FOR CLIPPING, but it
// DOES NOT tell you whether the edge is "entering" or "leaving".
// But you can use tests like Edge::Point_Side() to figure that out.
//======================================================================
float LineSeg::
Cross_Param(LineSeg e)
//======================================================================
{
float dx1, dy1, dx2, dy2;
float denom, s;
// This computation comes from writing each segment in parametric form,
// and solving a simulataneous equation to determine the parameter
// value of the intersection point on this LineSeg.
dx1 = e.end[0] - e.start[0];
dy1 = e.end[1] - e.start[1];
dx2 = end[0] - start[0];
dy2 = end[1] - start[1];
if ( ( denom = dx2 * dy1 - dy2 * dx1 ) == 0.0 )
// Parallel segments.
return 1.0e20f;
s = ( e.start[0] - start[0] ) * dy1 - ( e.start[1] - start[1] ) * dx1;
return s / denom;
}
point LineSeg::
Cross_Param_point(LineSeg e)
//======================================================================
{
float dx1, dy1, dx2, dy2;
float denom, s;
// This computation comes from writing each segment in parametric form,
// and solving a simulataneous equation to determine the parameter
// value of the intersection point on this LineSeg.
dx1 = e.end[0] - e.start[0];
dy1 = e.end[1] - e.start[1];
dx2 = end[0] - start[0];
dy2 = end[1] - start[1];
if ( ( denom = dx2 * dy1 - dy2 * dx1 ) == 0.0 )
// Parallel segments.
denom = 0.01;
s = ( e.start[0] - start[0] ) * dy1 - ( e.start[1] - start[1] ) * dx1;
float balance = s / denom;
point res(start[0] + ( end[0] - start[0] ) * balance, start[1] + (
end[1] - start[1] ) * balance);
return res;
}/************************************************************************
File: LineSeg.h
Author:
Stephen Chenney, schenney@xxxxxxxxxxx
Modifier
Yu-Chi Lai, yu-chi@xxxxxxxxxxx
Comment:
(c) 2001-2002 Stephen Chenney,
University of Wisconsin at Madison
Class header file for LineSeg
class.
Platform: Visio Studio.Net 2003 (converted to 2005)
*************************************************************************/
#ifndef _LINESEG_H_
#define _LINESEG_H_
#include "Edge.h"
struct point
{
point(){}
point(float _x, float _y):x(_x),y(_y)
{}
float x,y;
};
class LineSeg {
public:
// First constructor takes the endpoints.
LineSeg(float xs, float ys, float xe, float ye);
// Second constructor takes an edge. The LineSeg created has
the same
// start and end points as the edge.
LineSeg(Edge*);
LineSeg(){}
public:
// Return the parameter value at which this segment crosses the
given
// segment. This will return parameter values outside the range
0,1
// THIS FUNCTION IS EXTREMELY USEFUL FOR CLIPPING, but it
// DOES NOT tell you whether the edge is "entering" or
"leaving".
// But you can use tests like Edge::Point_Side() to figure that
out.
float Cross_Param(LineSeg);
point Cross_Param_point(LineSeg);
public:
float start[2]; // Starting point, x and y.
float end[2]; // Ending point, x and y.
};
#endif
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