I used plot3. when I try to rotate the 3D image, it is too slow to rotate for each time.

hFig = figure('name','3D Plotting_Solve_Pyramid','numbertitle','off'); hold on;

set(gcf,'Renderer','OpenGL'); % might improve performance

hAxes = gca;

for row = 1:hightl

      for col = 1:4:widthl

          objcolor = double(I2(row,col,:))./255.0;

          if objectpoint(row,col,3) >= -2.0 %&& (sum(objcolor)>0.3)
               plot3(hAxes, objectpoint(row,col,1), objectpoint(row,col,2), objectpoint(row,col,3), '.', 'MarkerEdgeColor',objcolor);

          end

      end
  end
  %Set up the view.
  xlabel(' X axis');
  ylabel(' Y axis');
  zlabel(' Z axis');

grid on;

cameratoolbar show;

axis vis3d;

axis equal;

Answer 1

[Mike Garrity]

I'm guessing that widthl and hightl are fairly large. This means that you're creating a large number of objects which are each drawing a single point. That's not a very efficient way to do it. You'll be much better off batching them up into a single object. A modern GPU is optimized for drawing large batches of geometry, not for drawing large numbers of tiny batches.

I discussed that in quite a bit of detail in this blog post and this blog post.

It looks like it'd actually be quite simple in this case. It's probably something like:

x = objectpoint(:,:,1);
y = objectpoint(:,:,2);
z = objectpoint(:,:,3);
r = double(x) / 255;
g = double(y) / 255;
b = double(z) / 255;
mask = (z(:)>=-2) & (r(:)+g(:)+b(:) > .3);  
scatter3(hAxes,x(mask),y(mask),z(mask),[],[r(mask), g(mask), b(mask)],'.')

On my system, with a Quadro K600 on R2015a, that runs at over 10 million markers per second. You could probably do better with a bit of tweaking, but that's about 120 frames per second for this image:

[Houghton]

I used your code to run my data but nothing show up in the figure.

There is an error.

" Error using scatter3 (line 45) Wrong number of input arguments. "

[Mike Garrity]

I'm not sure. Here's the entire piece of code I ran to get that picture:

close all
clear all
objectpoint = imread('ngc6543a.jpg');
hAxes=gca
x = objectpoint(:,:,1);
y = objectpoint(:,:,2);
z = objectpoint(:,:,3);
r = double(x) / 255;
g = double(y) / 255;
b = double(z) / 255;
mask = (z(:)>=-2) & (r(:)+g(:)+b(:) > .3);
scatter3(hAxes,x(mask),y(mask),z(mask),[], ...
         [r(mask), g(mask), b(mask)],'.')

There was a typo. I had x,y,z in the color field instead of r,g,b. I don't think that would have resulted in the error you have though.

[Houghton]

I corrected my code. Now I can ran my code to get the correct figure.

Thanks

[Houghton]

From scatter3(hAxes,x(mask),y(mask),z(mask),[], ... [r(mask), g(mask), b(mask)],'.')

What does [] mean in this command?

[Walter Roberson]

"If S is empty, then the default size of 36 points squared is used."