C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Random Colors For Use In Defining Different Regions          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Adam Hartshorne Guest Posted: Sat Jan 28, 2006 1:15 am    Post subject: Random Colors For Use In Defining Different Regions Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam Back to top Adam Hartshorne Guest Posted: Sat Jan 28, 2006 1:15 am    Post subject: Re: Random Colors For Use In Defining Different Regions Mike Wahler wrote: Quote: "Adam Hartshorne" <adam (AT) dcs (DOT) warwick.ac.uk> wrote in message news:43daaa5f$1_3@mk-nntp-2.news.uk.tiscali.com... Adam Hartshorne wrote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam I think I should have said I obviously know how to produce 3 random numbers to plug into RGB, but I was looking for a more sensible arrangement than this. I don't understand why you call it 'not sensible' Also, I should have added I'm also looking to be able limit the range of the colors as well. Say to avoid ever having black or white etc. You could generate a (pseudo)random number withing a specified range. See the C FAQ for details. If any undesired values fall inside a range, you can define several ranges, delimited by the undesired values, and randomly select a range before randomly selecting a value from it. If necessary you could also use the same approach to randomly select 'cells' or ranges of cells in your mesh. -Mike However that isn't making any conditions that the n number of colors created are differing in appearance. You can limit the range of the random numbers for the creation of each R,G and B value, but that makes no stipulation that a color maybe not be used because a similar one has already been created. Adam Back to top Mike Wahler Guest Posted: Sat Jan 28, 2006 1:15 am    Post subject: Re: Random Colors For Use In Defining Different Regions "Adam Hartshorne" <adam (AT) dcs (DOT) warwick.ac.uk> wrote in message news:43daaa5f$1_3@mk-nntp-2.news.uk.tiscali.com... Quote: Adam Hartshorne wrote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam I think I should have said I obviously know how to produce 3 random numbers to plug into RGB, but I was looking for a more sensible arrangement than this. I don't understand why you call it 'not sensible' Quote: Also, I should have added I'm also looking to be able limit the range of the colors as well. Say to avoid ever having black or white etc. You could generate a (pseudo)random number withing a specified range. See the C FAQ for details. If any undesired values fall inside a range, you can define several ranges, delimited by the undesired values, and randomly select a range before randomly selecting a value from it. If necessary you could also use the same approach to randomly select 'cells' or ranges of cells in your mesh. -Mike Back to top Adam Hartshorne Guest Posted: Sat Jan 28, 2006 1:15 am    Post subject: Re: Random Colors For Use In Defining Different Regions Adam Hartshorne wrote: Quote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam I should have added I'm also looking to be able limit the range of the colors as well. Say to avoid ever having black or white etc. Adam Back to top Adam Hartshorne Guest Posted: Sat Jan 28, 2006 1:15 am    Post subject: Re: Random Colors For Use In Defining Different Regions Adam Hartshorne wrote: Quote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam I think I should have said I obviously know how to produce 3 random numbers to plug into RGB, but I was looking for a more sensible arrangement than this. Also, I should have added I'm also looking to be able limit the range of the colors as well. Say to avoid ever having black or white etc. Adam Back to top Adam Hartshorne Guest Posted: Sat Jan 28, 2006 1:15 am    Post subject: Re: Random Colors For Use In Defining Different Regions Adam Hartshorne wrote: Quote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam I think I should have said I obviously know how to produce 3 random numbers to plug into RGB, but I was looking for a more sensible arrangement than this. Also, I should have added I'm also looking to be able limit the range of the colors as well. Say to avoid ever having black or white etc. Adam Back to top Mike Wahler Guest Posted: Sat Jan 28, 2006 2:38 am    Post subject: Re: Random Colors For Use In Defining Different Regions "Adam Hartshorne" <adam (AT) dcs (DOT) warwick.ac.uk> wrote in message news:43dab25d$1_3@mk-nntp-2.news.uk.tiscali.com... Quote: Mike Wahler wrote: "Adam Hartshorne" <adam (AT) dcs (DOT) warwick.ac.uk> wrote in message news:43daaa5f$1_3@mk-nntp-2.news.uk.tiscali.com... Adam Hartshorne wrote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam I think I should have said I obviously know how to produce 3 random numbers to plug into RGB, but I was looking for a more sensible arrangement than this. I don't understand why you call it 'not sensible' Also, I should have added I'm also looking to be able limit the range of the colors as well. Say to avoid ever having black or white etc. You could generate a (pseudo)random number withing a specified range. See the C FAQ for details. If any undesired values fall inside a range, you can define several ranges, delimited by the undesired values, and randomly select a range before randomly selecting a value from it. If necessary you could also use the same approach to randomly select 'cells' or ranges of cells in your mesh. -Mike However that isn't making any conditions that the n number of colors created are differing in appearance. If the RGB values are different, the colors will be different. Admittedly, the human eye cannot easily distinguish among colors with very close values. BUT: Again, you can impose your own restrictions upon the sets of values you generate. E.g. delimit your ranges, such as: make sure all red values are at least some distance (value) apart. E.g. if your possible range is from 500 to 32000, generate a random value between 5 and 320, and then multiply it by 100. You could do this with any size factor you like (e.g. 5,10, 32). Just remember if you want to include the highest and lowest possible values in the set, use a factor that divides it evenly. If you want to exclude the first 'x' values from the set, just use 'x' as the bottom of your range. Use the same technique to exclude from the highest 'x' values. All this isn't really a language issue, but of algorithms, applicable in any language. All I can say in closing is to try to be creative. -Mike Back to top Martin Eisenberg Guest Posted: Sat Jan 28, 2006 6:00 pm    Post subject: Re: Random Colors For Use In Defining Different Regions Adding to what Mike wrote, you might prefer the HSL or HSV color spaces over RGB for random generation. http://en.wikipedia.org/wiki/HSL_color_space http://en.wikipedia.org/wiki/HSV_color_space Martin -- Quidquid latine scriptum sit, altum viditur. Back to top David Harmon Guest Posted: Sat Jan 28, 2006 9:00 pm    Post subject: Re: Random Colors For Use In Defining Different Regions On Fri, 27 Jan 2006 23:08:44 +0000 in comp.lang.c++, Adam Hartshorne <adam (AT) dcs (DOT) warwick.ac.uk> wrote, Quote: I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. I would suggest generating an even spread of colors (where you have to define both "spread" and "even") then arranging them into random order with std::random_suffle(). But this isn't really a C++ question; you might do better in comp.graphics.algorithms Back to top rossum Guest Posted: Sat Jan 28, 2006 10:00 pm    Post subject: Re: Random Colors For Use In Defining Different Regions On Fri, 27 Jan 2006 23:08:44 +0000, Adam Hartshorne <adam (AT) dcs (DOT) warwick.ac.uk> wrote: Quote: Hi All, I was wondering if somebody could post a few lines of code which would produce random colors, which will be used in defining different regions on a mesh. So in addition to having n random colors, I feel that there should also be some condition to ensure that they aren't too similar in appearance, given that is likely to range from 2-20 say. Any help much appreciated, Adam Each individual colour value in RGB ranges from 0 to 255. Start by picking a set of reasonably well separated values from the whole range, say: 20, 60, 100, 140, 180, 220. Avoid 0 and 255 if you want to avoid white and black. Randomly pick one of these for the Red component. Randomly pick a different one for the Green and a different one again for the Blue. If you don't mind shades of grey then they don't even have to be different. If they do have to be different then swap the one picked with the end value in the preset list and pick any one except the last. Pseudocode: colourPresets = { 20, 60, 100, 140, 180, 220 } presetLast = 5 colourIndex = colourPresets[random(0 to presetLast)] redComponent = colourPresets[colourIndex] swap(colourPresets[colourIndex], colourPresets[presetLast]) decrement presetLast colourIndex = colourPresets[random(0 to presetLast)] greenComponent = colourPresets[colourIndex] swap(colourPresets[colourIndex], colourPresets[presetLast]) decrement presetLast colourIndex = colourPresets[random(0 to presetLast)] greenComponent = colourPresets[colourIndex] Alternatively just preselect 20 or so suitable colours as others have suggested. rossum -- The ultimate truth is that there is no ultimate truth Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.