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Richard145
12-08-2006, 12:11 PM
Please Help,

I am trying to animate the state of a model (built with Triangular shapes) at various time steps. I would like to save the states of the model as a series of .ppm (or some other image file format)at each time step and then render the images in sequence (kind of like an animated "flip-book").

I am so new to OpenGL, I am unsure of even where to start. Is there a link or some simple code examples to illustrate this?

Thanks in advance for ANY help/hints.

ZbuffeR
12-09-2006, 03:38 AM
So you want to do, for each time step :

1) draw model with triangles.
glBegin(GL_TRIANGLES)
glVertex3f(...);
...
glEnd();

2) get back image from openGL frame buffer to an array.
glReadPixels(...);
http://www.opengl.org/resources/faq/technical/rasterization.htm#rast0015

3) write the image data array to file, using an image library or doing it yourself.
The ppm and its family is pretty simple to do : http://netpbm.sourceforge.net/doc/ppm.html


Then, once images are written, you load them from the disk (either all at once or one by one, depends of the total size of course), and display them : to display using OpenGL you have 2 ways :
A) glDrawPixels(), see link for glReadPixels
B) use a texture mapped quad : needs a bit more opengl knowledge, but the fastest way, specially if you can store each image in a texture before hand, and just switch current texture.

free free to ask for more details on one or all these steps ;)