?
Solved

OpenGL Help with drawLine Function

Posted on 2011-09-28
2
Medium Priority
?
605 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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 16

Accepted Solution

by:
George Tokas earned 1000 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 1000 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

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
The goal of this video is to provide viewers with basic examples to understand recursion in the C programming language.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

777 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