open gl static drawing

Question

0.00/5 (No votes)

See more:

i am developing a paint like application using opengl with c++. But everytime i draw an object using mouse the previous image or object is lost. how can i solve this please help!

Posted 23-Jun-11 19:53pm

prison

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Cedric Moonen · Answer 1 · 2011-06-23T20:39:00

This is the default behaviour and should be kept this way. You need to redraw your full "model" for each screen. This means that when the user draws a line, instead of immediately drawing, you should keep its properties in memories (along with all previous lines drawn) and trigger a refresh of the screen (in OpenGL, you would most probably have a main loop that refreshes the screen at a specific rate).
In your draw function, you would then need to redraw all your elements.

enhzflep · Answer 2 · 2011-06-24T00:36:00

From what I understand, each time openGL draws a frame, it culls whatever was there last time. So each frame you need to specify the location/transformation of each object + camera + lights.

In order to display more than 1 object, you'll need a way of storing information about this object that can be used when drawing it.

So, each time you create an object with the mouse, save all the information needed to draw it & add this information to a list(that you create and maintain) of all objects in the scene.

Then when it comes time to draw the scene, just step through the list of created objects, transforming & drawing each one as you go.

simple openGlut pseudocode may resemble:

myDrawFunc
vector pos1, pos2

glLoadIdentity
glTranslatef(pos1)
-- do the steps to draw object1
..
..
..

glLoadIdentity
glTranslatef(pos2)
do the steps to draw object2
..
..
..

I'm only _very_ new to this, having first tried my hand at openGL earlier this week. But this is the understanding that I (think?!) I have.
Cheers. :)

open gl static drawing

2 solutions

Solution 1

Solution 3

Add your solution here

Preview 0