Solved

OpenGL Help with drawLine Function

Posted on 2011-09-28
2
598 Views
Last Modified: 2013-12-06
Hello Everyone,

I am writing a program in which I must implement the mid-point line algorithm to draw a line.  I have the algorithm working but I am unable to figure out why the line is not displaying to the screen.  BTW I can only use glVertex to plot each pixel. Below is the drawLine function.
void drawLine(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2)
{
	GLfloat pk;
	GLfloat pk1;
	GLfloat color = 1.23234;
	Point2D vertex;
	Point2D slope;
	slope.x = x2 - x1;
	slope.y = y2 - y1;

	pk = ((2*slope.y) - slope.x);

	vertex.x = x1;
	vertex.y = y1;

	glColor3f(5.0f, 3.0f, 2.0f);

	for(; vertex.x <= x2; vertex.x++)
	{
		if(pk < 0 )
		{
			//vertex.x++;
			glBegin(GL_POINTS);
			glVertex2f(vertex.x, vertex.y);
			glEnd();
			vertex.round();
			//mySetPixel(vertex.x, vertex.y, &color);
			pk1 = pk + 2 * (slope.y);
			pk = pk1;
		}
		else
		{
			//vertex.x++;
			vertex.y++;
			glBegin(GL_POINTS);
			glVertex2f(vertex.x, vertex.y);
			glEnd();
			pk1 = pk + 2 * (slope.y) - 2 * (slope.x);
			pk = pk1;
		}
	}

Open in new window

0
Comment
Question by:brich744
2 Comments
 
LVL 16

Accepted Solution

by:
George Tokas earned 250 total points
ID: 36813269
Why don't you use the line functions?
glBegin(GL_LINES);
glVertex3f(vertex1.x, vertex1.y,vertex1.z);
glVertex3f(vertex2.x, vertex2.y,vertex2.z);
glEnd();
The certex declaration will be for 3 dimentions where z = 0.
Change the width of the line with: glLineWidth() and don't forget for antialiasing the GL_LINE_SMOOTH parameter.

George Tokas.

0
 
LVL 12

Assisted Solution

by:HappyCactus
HappyCactus earned 250 total points
ID: 36813743
What is the GL_POINT_SIZE query result? what about setting the glpointsize() value?
Are the gl context correctly setup? try to draw a simple triangle, does it display correctly? if not, maybe your problem is not how the line is drawn, but how your GL environment is setup.
0

Featured Post

IT, Stop Being Called Into Every Meeting

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

Join & Write a Comment

Templates For Beginners Or How To Encourage The Compiler To Work For You Introduction This tutorial is targeted at the reader who is, perhaps, familiar with the basics of C++ but would prefer a little slower introduction to the more ad…
Performance in games development is paramount: every microsecond counts to be able to do everything in less than 33ms (aiming at 16ms). C# foreach statement is one of the worst performance killers, and here I explain why.
The goal of this video is to provide viewers with basic examples to understand and use switch statements in the C programming language.
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

760 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

19 Experts available now in Live!

Get 1:1 Help Now