"OpenGL Basics"--encapsulating OpenGL functions using an object-oriented approach (II)

Today, a line class is encapsulated. Responsible for drawing lines on the form that was written yesterday.

OpenGL drawing is achieved by setting a number of parameters to the Glbegin function, with three different parameters for drawing a line:

Gl_lines: Draw a segment that connects two points (the drawn endpoint is between the Glbegin function and the Glend function)

Gl_line_strip: Draw End-to-end polyline

Gl_line_loop: Draws the end-to-end polyline and connects the starting and ending points at the last. Closed path

The following is the code for the line class:

/*********************************************** file Name: Line.h function: Canvas. You can draw dots, lines and ellipses, rectangular ************************************************/#ifndef _line_h_#define _line_h_#include " Point.h "#include" Window.h "class Line:public Object {Public:line () {This->mode = this->line_mode_default;this- >status = This->line_init;} Starting point, set the starting point each time. All at the same time the record is at the start point State. If this is already the starting point//Then delete the previous starting point void MoveTo (point& p) {if (This->status = = This->line_start) {points.pop_back (); return;} Points.push_back (p); this->status = This->line_start;} Draw the end point of the line, if it starts at the end point. Forbid join void LineTo (point& p) {if (This->status = = This->line_start) {this->points.push_back (P);this-> status = This->line_end;return;}} Join the node array void addpoints (point* p,int size) {for (int i = 0; i < size; i++) {this->points.push_back (p[i]);}} Set Line color void SetColor (color& color) {this->color = color;} Set draw line mode void SetMode (int mode) {switch (mode) {case line_mode_default:mode = gl_lines; break;case Line_mode_loop:mode = GL _line_loop; Break;case Line_mode_notloop:mode = Gl_line_strip; break;} This->mode = mode;} public:static const int line_mode_loop = 0;//Set Line end-to-end static const int Line_mode_notloop = 1;//do not set line end-to-end static const int LI Ne_mode_default = 2;//Default Draw segment private://draw line State static const int line_init = 0;//initial state static const int Line_start = 1;//start Point State STA Tic const int line_end = 2;//end point State private:int mode;//Draw line mode, default feel does not connect vector<point> points;//point set int status;//draw line State color color;//Specifies the color public:void show () {//will be called by window to paint the virtual function glcolor3f (color. R, color. G, color. B); Glbegin (mode); for (int i = 0; i < points.size (); i++) {glvertex2i (Points[i]). X, Points[i]. Y);} Glend ();}}; #endif

Here is an example of a pentagram:

(Inside the window and application, point class in the blog (a))

#include "Window.h" #include "Application.h" #include "Line.h"//Hide Console form #pragma comment (linker, "/subsystem:\" windows\ "/entry:\" Maincrtstartup\ "") int main (int argc, char* argv[]) {int w = N, h = 300; Window window (String ("Hello"), Window.create, W, h); Line line;//to draw the Pentagram Line.setmode (line. Line_mode_loop); Point P[5] = {Point (ten, a), point (+), point (+), point (+), point (+),};line.setcolor (Color (255, 0, 0)); line.addpoints (P, 5); Window.add (&line); application* app = new Application (), App->init (argc, argv), App->add (window), app->show ();d elete App;return 0;} //*/

：

This is the direct use of OpenGL's line-drawing function. The computer graphics algorithm used to draw straight line has DDA algorithm and Bresenham algorithm.

"OpenGL Basics"--encapsulating OpenGL functions using an object-oriented approach (II)