Re: [GRASS-user] r.out.pov scale question
Adam, find attached my (old) r.out.povscript script which does the needed calculations. Perhaps giving some ideas. the Povray scales are a bit tricky. cheers Markus On Wed, Oct 27, 2010 at 6:07 PM, Adam Dershowitz, Ph.D., P.E. adershow...@exponent.com wrote: I have been trying to use r.out.pov but something is not clear to me from the documentation, and examples I can find on the web. If I use hftype=0 (the default) then, as I understand it it, each step, from 0-65535 represents one map unit (meters in my case). That is giving me too much stair-stepping in POVRAY. I think that part of the issue is that there is too much rounding of elevations. So, I decided to try hrtype=1. As I understand it that will scale the height of the image to use more of the range (my map just goes from 61-1086 meters). But, I can't seem to figure out how much it scales by. There is also the scale= option in r.out.pov, but I am not sure if that is a multiplier or a divider? This is important because I need to then scale the heighfield in my POV file. If I use hrtype=0 then this is correct: scale dx, 65535, dy But, if I use hftype=1, what is the correct value for the above scale command? Is it 65535/1086 (max height in the map?) 65535/(1086-61) (vertical range of my map?) If I use scale=10 then should it be? scale dx, 65535/10, dy scale dx, 65535*10, dy scale dx, 10, dy Or should I use scale=0.1? Or should I use r.out.pov scale=65535/1086 Thanks, --Adam ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user r.out.povscript Description: Binary data ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.out.pov scale question
Thanks. This is helpful for some ideas. Although, it uses a vertical scale that is just a constant of 65535. But, my followup email probably crossed with yours. --Adam On Nov 3, 2010, at 4:22 AM, Markus Neteler wrote: Adam, find attached my (old) r.out.povscript script which does the needed calculations. Perhaps giving some ideas. the Povray scales are a bit tricky. cheers Markus On Wed, Oct 27, 2010 at 6:07 PM, Adam Dershowitz, Ph.D., P.E. adershow...@exponent.com wrote: I have been trying to use r.out.pov but something is not clear to me from the documentation, and examples I can find on the web. If I use hftype=0 (the default) then, as I understand it it, each step, from 0-65535 represents one map unit (meters in my case). That is giving me too much stair-stepping in POVRAY. I think that part of the issue is that there is too much rounding of elevations. So, I decided to try hrtype=1. As I understand it that will scale the height of the image to use more of the range (my map just goes from 61-1086 meters). But, I can't seem to figure out how much it scales by. There is also the scale= option in r.out.pov, but I am not sure if that is a multiplier or a divider? This is important because I need to then scale the heighfield in my POV file. If I use hrtype=0 then this is correct: scale dx, 65535, dy But, if I use hftype=1, what is the correct value for the above scale command? Is it 65535/1086 (max height in the map?) 65535/(1086-61) (vertical range of my map?) If I use scale=10 then should it be? scale dx, 65535/10, dy scale dx, 65535*10, dy scale dx, 10, dy Or should I use scale=0.1? Or should I use r.out.pov scale=65535/1086 Thanks, --Adam ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user r.out.povscript ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] r.out.pov scale question
I have not heard anything back on this, so decided to go to the source code of r.out.pov. I figured out the answer and wanted to post it, in case it is useful to anyone else, or someone might want to add it to the help page. Here is what I figured out. 1) scale, and hftype are independent. So, first each cell is multiplied by scale (so, if a cell elevation is 12m and scale is 10, then the new value is 120.) The default value of scale is 1.0. If hftype is set to 1, then each cell is multiplied by 65535/(maximum elevation value in the map). So, when using hftype=1, the correct scaling in the POV ray file is the maximum height in the map. For example, if the maximum elevation is 1086 m, then this should go in the POV file: scale 1391, 1086, 1810 // dx,dz,dy of extent in meters Finally, I believe that there is a bug in r.out.pov! It seems that bias is read in, in order to apply a bias to the height field, however hfBias is the variable that is actually being used for the calculations, and it is never assigned a value. And bias is not actually used in any calculations. --Adam On Oct 27, 2010, at 9:07 AM, Adam Dershowitz, Ph.D., P.E. wrote: I have been trying to use r.out.pov but something is not clear to me from the documentation, and examples I can find on the web. If I use hftype=0 (the default) then, as I understand it it, each step, from 0-65535 represents one map unit (meters in my case). That is giving me too much stair-stepping in POVRAY. I think that part of the issue is that there is too much rounding of elevations. So, I decided to try hrtype=1. As I understand it that will scale the height of the image to use more of the range (my map just goes from 61-1086 meters). But, I can't seem to figure out how much it scales by. There is also the scale= option in r.out.pov, but I am not sure if that is a multiplier or a divider? This is important because I need to then scale the heighfield in my POV file. If I use hrtype=0 then this is correct: scale dx, 65535, dy But, if I use hftype=1, what is the correct value for the above scale command? Is it 65535/1086 (max height in the map?) 65535/(1086-61) (vertical range of my map?) If I use scale=10 then should it be? scale dx, 65535/10, dy scale dx, 65535*10, dy scale dx, 10, dy Or should I use scale=0.1? Or should I use r.out.pov scale=65535/1086 Thanks, --Adam ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
