Nested foreach functioning unpredictably when drawing colored spheres in 3 dimensions

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7
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I'm visualising color systems with TikZ to my students, and here I'm creating a 3D set of axes which represent red, green, blue and their combinations as shaded spheres.

RGB space

For some reason, the result looks alright on the Blue axis, but doesn't work as expected on Green and Red axes as when their values are increased the spheres stay gray. Where's the problem?

I've taken care that everything is represented in code in the same order, RGB. Code first sets up some variables about axes (x, y, z), then step size/distance between spheres and then the max value for assumed 8-bit color, 255.

The point is that the nested for eaches go through all integer values between 0Ã¢Â€Â“255 for red, green and blue (all combinations), the second tikzmath creates scaled variables to be used with color information, and then with every pass a shaded sphere is drawn with the proper color and positioning on the axes.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=red/maxvalue*100;greens=green/maxvalue*100;blues=blue/maxvalue*100;

shadedraw[ball color=red!reds!green!greens!blue!blues!] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture

enddocument

asked Aug 26 at 4:41

JoonasD6

937

add a commentÂ |Â

up vote
7
down vote

favorite

I'm visualising color systems with TikZ to my students, and here I'm creating a 3D set of axes which represent red, green, blue and their combinations as shaded spheres.

RGB space

For some reason, the result looks alright on the Blue axis, but doesn't work as expected on Green and Red axes as when their values are increased the spheres stay gray. Where's the problem?

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=red/maxvalue*100;greens=green/maxvalue*100;blues=blue/maxvalue*100;

shadedraw[ball color=red!reds!green!greens!blue!blues!] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture

enddocument

asked Aug 26 at 4:41

JoonasD6

937

add a commentÂ |Â

up vote
7
down vote

favorite

I'm visualising color systems with TikZ to my students, and here I'm creating a 3D set of axes which represent red, green, blue and their combinations as shaded spheres.

RGB space

For some reason, the result looks alright on the Blue axis, but doesn't work as expected on Green and Red axes as when their values are increased the spheres stay gray. Where's the problem?

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=red/maxvalue*100;greens=green/maxvalue*100;blues=blue/maxvalue*100;

shadedraw[ball color=red!reds!green!greens!blue!blues!] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture

enddocument

asked Aug 26 at 4:41

JoonasD6

937

I'm visualising color systems with TikZ to my students, and here I'm creating a 3D set of axes which represent red, green, blue and their combinations as shaded spheres.

RGB space

For some reason, the result looks alright on the Blue axis, but doesn't work as expected on Green and Red axes as when their values are increased the spheres stay gray. Where's the problem?

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=red/maxvalue*100;greens=green/maxvalue*100;blues=blue/maxvalue*100;

shadedraw[ball color=red!reds!green!greens!blue!blues!] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture

enddocument

asked Aug 26 at 4:41

JoonasD6

937

asked Aug 26 at 4:41

JoonasD6

937

asked Aug 26 at 4:41

JoonasD6

937

asked Aug 26 at 4:41

JoonasD6

937

add a commentÂ |Â

1 Answer
1

active

oldest

votes

up vote
8
down vote

accepted

I do not know precisely what went wrong but I guess that there is some sort of unitarity problem when the fractions do not add up to 100. Here is some other method that does what I think you want.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolorRGBreds,greens,blues

shadedraw[ball color=mycolor] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

enter image description here

EDIT: Appended a version with unique color names. With all these different viewers around one never knows. The output is the same.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolor-reds-greens-bluesRGBreds,greens,blues

shadedraw[ball color=mycolor-reds-greens-blues] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

edited Aug 26 at 15:51

answered Aug 26 at 8:40

marmot

55.7k461121

That is very close to how I initially tried to color the spheres; I thought definecolor didn't work for redefining as well? I'll give this one a shot (and might remove the maxvalue stuff altogether if I end up doing this completely in 8 bit anyway); thank you very much!
â€“Â JoonasD6
Aug 26 at 15:36

1

Did before I read your plea. You deserve it. Just had to test a bit further first. :)
â€“Â JoonasD6
Aug 26 at 15:43

@JoonasD6 Thanks! I added a second version with unique color names.
â€“Â marmot
Aug 26 at 15:52

add a commentÂ |Â

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
8
down vote

accepted

I do not know precisely what went wrong but I guess that there is some sort of unitarity problem when the fractions do not add up to 100. Here is some other method that does what I think you want.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolorRGBreds,greens,blues

shadedraw[ball color=mycolor] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

enter image description here

EDIT: Appended a version with unique color names. With all these different viewers around one never knows. The output is the same.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolor-reds-greens-bluesRGBreds,greens,blues

shadedraw[ball color=mycolor-reds-greens-blues] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

edited Aug 26 at 15:51

answered Aug 26 at 8:40

marmot

55.7k461121

That is very close to how I initially tried to color the spheres; I thought definecolor didn't work for redefining as well? I'll give this one a shot (and might remove the maxvalue stuff altogether if I end up doing this completely in 8 bit anyway); thank you very much!
â€“Â JoonasD6
Aug 26 at 15:36

1

Did before I read your plea. You deserve it. Just had to test a bit further first. :)
â€“Â JoonasD6
Aug 26 at 15:43

@JoonasD6 Thanks! I added a second version with unique color names.
â€“Â marmot
Aug 26 at 15:52

add a commentÂ |Â

up vote
8
down vote

accepted

I do not know precisely what went wrong but I guess that there is some sort of unitarity problem when the fractions do not add up to 100. Here is some other method that does what I think you want.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolorRGBreds,greens,blues

shadedraw[ball color=mycolor] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

enter image description here

EDIT: Appended a version with unique color names. With all these different viewers around one never knows. The output is the same.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolor-reds-greens-bluesRGBreds,greens,blues

shadedraw[ball color=mycolor-reds-greens-blues] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

edited Aug 26 at 15:51

answered Aug 26 at 8:40

marmot

55.7k461121

That is very close to how I initially tried to color the spheres; I thought definecolor didn't work for redefining as well? I'll give this one a shot (and might remove the maxvalue stuff altogether if I end up doing this completely in 8 bit anyway); thank you very much!
â€“Â JoonasD6
Aug 26 at 15:36

1

Did before I read your plea. You deserve it. Just had to test a bit further first. :)
â€“Â JoonasD6
Aug 26 at 15:43

@JoonasD6 Thanks! I added a second version with unique color names.
â€“Â marmot
Aug 26 at 15:52

add a commentÂ |Â

up vote
8
down vote

accepted

I do not know precisely what went wrong but I guess that there is some sort of unitarity problem when the fractions do not add up to 100. Here is some other method that does what I think you want.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolorRGBreds,greens,blues

shadedraw[ball color=mycolor] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

enter image description here

EDIT: Appended a version with unique color names. With all these different viewers around one never knows. The output is the same.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolor-reds-greens-bluesRGBreds,greens,blues

shadedraw[ball color=mycolor-reds-greens-blues] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

edited Aug 26 at 15:51

answered Aug 26 at 8:40

marmot

55.7k461121

I do not know precisely what went wrong but I guess that there is some sort of unitarity problem when the fractions do not add up to 100. Here is some other method that does what I think you want.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolorRGBreds,greens,blues

shadedraw[ball color=mycolor] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

enter image description here

EDIT: Appended a version with unique color names. With all these different viewers around one never knows. The output is the same.

documentclassmemoir
usepackagetikz
usetikzlibrarymath

begindocument

begintikzpicture[scale=0.03]
tikzmathx = 300; y = x; z=x; step=51;maxvalue=255; %optimal step size 51
draw[->, very thick, red] (0,0,0) -- (x,0,0) node[right]R;
draw[->, very thick, green] (0,0,0) -- (0,y,0) node[above]G;
draw[->, very thick, blue] (0,0,0) -- (0,0,z) node[below left]B;

foreach red in 0,step,...,maxvalue
 foreach green in 0,step,...,maxvalue
 foreach blue in 0,step,...,maxvalue

tikzmathreds=(red/maxvalue)*255;
greens=(green/maxvalue)*255;blues=(blue/maxvalue)*255;
definecolormycolor-reds-greens-bluesRGBreds,greens,blues

shadedraw[ball color=mycolor-reds-greens-blues] (red,green,blue) circle [radius=10cm];
 
 


endtikzpicture
enddocument

edited Aug 26 at 15:51

answered Aug 26 at 8:40

marmot

55.7k461121

edited Aug 26 at 15:51

answered Aug 26 at 8:40

marmot

55.7k461121

answered Aug 26 at 8:40

marmot

55.7k461121

answered Aug 26 at 8:40

marmot

55.7k461121

That is very close to how I initially tried to color the spheres; I thought definecolor didn't work for redefining as well? I'll give this one a shot (and might remove the maxvalue stuff altogether if I end up doing this completely in 8 bit anyway); thank you very much!
â€“Â JoonasD6
Aug 26 at 15:36

1

Did before I read your plea. You deserve it. Just had to test a bit further first. :)
â€“Â JoonasD6
Aug 26 at 15:43

@JoonasD6 Thanks! I added a second version with unique color names.
â€“Â marmot
Aug 26 at 15:52

add a commentÂ |Â

That is very close to how I initially tried to color the spheres; I thought definecolor didn't work for redefining as well? I'll give this one a shot (and might remove the maxvalue stuff altogether if I end up doing this completely in 8 bit anyway); thank you very much!
â€“Â JoonasD6
Aug 26 at 15:36

1

Did before I read your plea. You deserve it. Just had to test a bit further first. :)
â€“Â JoonasD6
Aug 26 at 15:43

@JoonasD6 Thanks! I added a second version with unique color names.
â€“Â marmot
Aug 26 at 15:52

That is very close to how I initially tried to color the spheres; I thought definecolor didn't work for redefining as well? I'll give this one a shot (and might remove the maxvalue stuff altogether if I end up doing this completely in 8 bit anyway); thank you very much!
â€“Â JoonasD6
Aug 26 at 15:36

Did before I read your plea. You deserve it. Just had to test a bit further first. :)
â€“Â JoonasD6
Aug 26 at 15:43

@JoonasD6 Thanks! I added a second version with unique color names.
â€“Â marmot
Aug 26 at 15:52

add a commentÂ |Â

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