high resolution screenshots

OpenGL Development JOGL Development
#1

Hey, this may be a bit of a newbie question. I’d like to try to find a way to take high resolution, eg poster-sized screenshots of my Jogl app.

PBuffers work, but it looks like they’re limited by the video card’s maximum resolution. And I can’t rely on the currentness of my user base’s hardware - it sounds like older hardware may not support PBuffers.

It looks like Unix’s OpenGL has a software rendered PixMap method (GLX.glxCreatePixmap), and that there is a way to do a similar thing in Windows (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/opengl/oglport_286d.asp).

Is there a standard way in Jogl of doing software rendering that may have a higher maximum resolution than PBuffers allow?

#2

Not directly. The standard technique for doing this is tiled rendering. The scene is rendered repeatedly, changing the view frustum each time to achieve non-overlapping pieces of the larger image. The overall image is then assembled afterward in an image editor. Here are a couple of links:

http://www.mesa3d.org/brianp/sig97/offscrn.htm (found with a Google search for “tiled rendering utility” – I assume you can find the source code somewhere)

http://croquetweak.blogspot.com/2005/03/print-quality-screenshots.html (found with a Google search for “opengl high resolution screenshot frustum”)

Either way you’ll need to port the tiled rendering code to Java, but this shouldn’t be too difficult.

#3

[quote]Either way you’ll need to port the tiled rendering code to Java, but this shouldn’t be too difficult.
[/quote]
No you don’t, because I’ve already done it!

See here for the code.

#4

Huh. The forum didn’t post my response.

Anyway, thanks a lot - that’s exactly what I need.

But I’m having difficulties with matrices now. I have both a gluPerspective (replaced with trPerspective outside the tiling loop as prescribed) and a gluLookAt() call in my drawing code. The matrix code isn’t mine, so I don’t understand it well.

Any guidance? I’ll try to read up on these matrix operations a bit more in the meantime.

#5

Glad to see someone getting some use out of it :slight_smile:

re matrices: I’m a bit weak in this area too, but I’ll have a poke around in my own code and see if I can isolate what I did. I’m a bit busy at the moment though, so bear with me.

#6

Excellent! Thanks. I’ve filed an RFE to incorporate this class into com.sun.opengl.util.

#7

Ah, good, I got it working. Just some newbie issues.

  • I had to make sure that no matrix operations were being performed while gl.glMatrixMode(GL.GL_PROJECTION) was active. Operations on other matrices, like GL.GL_MODELVIEW do not affect the projection matrix.
  • Had to make sure that the tile size wasn’t larger than the current buffer I was displaying into. I’m using a GLCanvas inside a JPanel, so I just set the tile size to super.getHeight() and super.getWidth() for perfect results.

Also, to retrieve the image to a BufferedImage instead of a file, I took a tip from the new Screenshot class:

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
ByteBuffer imageBuffer = ByteBuffer.wrap(((DataBufferByte) image.getRaster().getDataBuffer()).getData());
…
tr.setImageBuffer(GL.GL_BGR, gl.GL_UNSIGNED_BYTE, imageBuffer);
…

#8

Thanks again for this contribution. The TileRenderer class has been incorporated into the com.sun.opengl.util package under BSD licensing terms with the permission of the author, Brian Paul, and a new demos.misc.TiledRendering demo has been added.

#9

Huzzah! Immortalised at last! (sort of)