Well, I guess the size itself is not a bug, but a feature of GLUT. But there is an inconsistency: The spec for glutStrokeCharacter

http://www.opengl.org/developers/documentation/glut/spec3/node78.html

talks about "units" (of magnitude 100, as you've already noticed), while the spec for glutStrokeWidth

http://www.opengl.org/developers/documentation/glut/spec3/node79.html

talks about "pixels". The latter is probably a cut-n-paste bug from the spec for glutBitmapWidth.

Just as I suspected. And here's what the glutStrokeWidth and glutStrokeLength man pages in the GLUT sources say: int glutStrokeWidth(void *font, int character); int glutStrokeLength(void *font, const unsigned char *string); glutStrokeWidth returns the width in modeling units of a stroke character in a supported stroke font glutStrokeLength returns the length in modeling units of a string (8-bit characters). This length is equivalent to summing all the widths returned by glutStrokeWidth for each character in the string. So the "int" return type (instead of GLdouble, as I expected) seems possible because of that "units" talk, and the "pixel" talk doesn't seem to belong there in the spec. Sigh, one just needs to know how to read the spec (and the source).. Okay, that gives me another chance to try silly things (centered or right-justified text blocks, in this case;-). Looking forward to "real" font add-ons to HOpenGL, of course, if Vincenzo gets round to it. Btw, while we are sharing tricks and plans - using feedback to output vectorized snapshots wasn't as difficult as I thought (as usual, the redbook_HS examples, here "Feedback.hs", were helpful). A dummy fragment for exporting SVG (http://www.w3.org/TR/SVG/) from HOpenGL is appended (just dealing with lines and polygons, just output the polygons as they come -> possibly incorrect output), and the more complete original for exporting EPS from OpenGL (output polygons in back-to-front order and emulate flat shading) can be found at: Mark Kilgard Achieving Quality PostScript output for OpenGL http://www.opengl.org/developers/code/mjktips/Feedback.html Unfortunately, the resulting vector graphics can be quite large, certainly larger that a JPEG snapshot:-(. They are scalable, which is nice, and with a bit of hacking, one could put several of them into an SVG file, and animate through the snapshots, but then the size problem becomes a real headache. Haven't tried compression yet, nor hidden polygon removal, but I'm currently not inclined to fill in the missing bits in the code, simply because I'm not using it - it was worth a try, though.. Cheers, Claus ----------------------------------- a little HOpenGL to SVG hack import Numeric(showGFloat) .. -- extract x and y coordinates from feedback info, ignore rest svgXYproject (ThreeDColor (Vertex3 x y z) (Prelude.Right (Color4 r g b a))) = (showGFloat (Just 2) x . showString "," . showGFloat (Just 2) (-y) . showString " ") "" -- extract rgb values from feedback info, ignore rest svgRGBproject (ThreeDColor (Vertex3 x y z) (Prelude.Right (Color4 r g b a))) = (showGFloat Nothing (r*100) . showString "%," . showGFloat Nothing (g*100) . showString "%, " . showGFloat Nothing (b*100) . showString "%") "" -- incomplete, as usual.. -- svg (PassThroughToken (PassThroughValue n)) = -- svg (PointToken i) = svg (LineToken i j) = "<polyline stroke=\"rgb("++svgRGBproject i++")\" " ++"points=\""++(concatMap svgXYproject [i,j])++"\"/>" -- what's this? svg (LineResetToken i j) = "<polyline stroke=\"rgb("++svgRGBproject i++")\" " ++"points=\""++(concatMap svgXYproject [i,j])++"\"/>" -- colour the polygon by its first vertex.. svg (PolygonToken is) = "<polygon fill=\"rgb("++svgRGBproject (head is)++")\" " ++"points=\""++(concatMap svgXYproject is)++"\"/>" svg _ = error "Author is too lazy for a complete svg FeedbackToken" -- Write contents of entire buffer. printBuffer :: GLint -> FeedbackBuffer -> IO () printBuffer size buffer = do Just tokens <- getFeedbackTokens size buffer (WindowPosition x y, WindowSize w h) <- get VarViewport putStrLn "<?xml version=\"1.0\" standalone=\"no\"?>" putStrLn "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 20010904//EN\"" putStrLn " \"http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd\">" putStrLn $ "<svg width=\""++show ((fromIntegral w)/50)++"cm\" " ++"height=\""++show ((fromIntegral h)/50)++"cm\" " ++"viewBox=\"0 0 "++show w++" "++show h++"\"" putStrLn " xmlns=\"http://www.w3.org/2000/svg\"" putStrLn " xmlns:xlink=\"http://www.w3.org/1999/xlink\">" putStrLn $ "<g transform=\"translate(0,"++show h++")\">" mapM_ (putStrLn . svg) tokens putStrLn "</g>" putStrLn "</svg>" -- main function, call this in your display callback instead of -- the direct rendering part (here assumed to be executing a -- display list) when you want to output a single scene as SVG. -- feedback buffer overflow tends to be the main error source, -- but I've got no idea how to estimate the size correctly.. printDisplay :: DisplayList -> DisplayAction printDisplay dl = do feedBuffer <- makeFeedbackBuffer 1048576 ThreeDColor' feedbackBuffer feedBuffer renderMode Feedback callList dl size <- renderMode Render printBuffer size feedBuffer freeFeedbackBuffer feedBuffer