RE: Mathematica's color limitations
- To: mathgroup at smc.vnet.net
- Subject: [mg34435] RE: [mg34406] Mathematica's color limitations
- From: "DrBob" <majort at cox-internet.com>
- Date: Sun, 19 May 2002 04:15:15 -0400 (EDT)
- Reply-to: <drbob at bigfoot.com>
- Sender: owner-wri-mathgroup at wolfram.com
When I evaluate your "color wheel" and use //Timing, it takes about 2.8 seconds. At the default size there are significant gaps as you've mentioned --- points uncolored --- but if I expand the chart manually, the gaps sometimes almost entirely disappear. Using ImageSize to expand the chart doesn't work as well, for some reason! Also, adding AspectRatio->Automatic to the Show command makes the wheel circular. Bobby -----Original Message----- From: Michael Math [mailto:michael-math at science.edu] To: mathgroup at smc.vnet.net Subject: [mg34435] [mg34406] Mathematica's color limitations Mathematica seems to have some limitations dealing with colors, and I was wondering if there are any workarounds or solutions to these problems. First, I am having a hard time getting my color output to display in the colors I specify. I am trying to make three dimensional plots which heavily involve color and require the output to be freely rotated to make sense of the image. The RealTime3D package does not obey the colors I give under Mathematica 4.0 (under Windows). Does anyone know if this has been fixed in 4.1? I have also tried the MathGL3d OpenGLViewer, but it does not work either. Basically what I am doing is creating a field of points, along these lines: pts = Table[{Hue[a,b,c],Point[{a,b,c}]}, {a,0,1,0.05},{b,0,1,0.05},{c,0,1,0.05}]; Show[Graphics3D[pts]]; This is the most basic form, however in other plots I am varying the size of the points and not drawing some of the points. The Default3D view draws everything fine, except that I can't rotate it freely. Yes I can draw several plots and animate them but it takes a long time and isn't quite the same - for example, I can't zoom in and out. RealTime3D displays all my points as black and fixed size. The OpenGLViewer does not give the right color to my points, but it seems to get the size ok. The color is the most important thing! The second problem I am having is that there does not seem to be any easy way to generate a plot where color is based on all the coordinates in the plot. As a result of this I have to resort to the above point method. All the cases where Mathematica lets you specify color seem to be through the ColorFunction option, which takes the z value in the plot as the input to the color function. This is not acceptable to me, as I need to know at least the x and y values in order to determine the color (and possibly z as well). So for example, to display a color wheel I have to do something like this: Show[Graphics[{ Table[{Hue[a/(2 Pi), 1, r], Point[N[{r*Sin[a], r*Cos[a]}]]}, {a, 0, 2 Pi, Pi/256}, {r, 0, 1, 0.01}] } ]]; This takes too long and even with all these points still does not fill in all the points in the circle. I have tried converting hues and rgb colors to flat integers, but then I wind up with 3D shapes that I am not sure how to generate - for example, in one case I appear to need the formula for something resembling an exponential spiral. Help? :-) Michael