View source for Gnuplot/C2/Generate-3D-plots-and-surfaces/English

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|| '''Visual Cue'''
|| '''Narration'''

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|| '''Slide Number 1'''
'''Title Slide '''
'''Generate 3D plot and surfaces'''
|| Welcome to the tutorial on '''Generate 3D plot and Surfaces'''.

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|| '''Slide Number 2'''
'''Learning Objectives'''
|| In this tutorial we will learn to,
* Generate a 3D plot with '''splot''' command
* Rotate to change the viewing angle
* Change the surface properties
* Color the two sides of the surface differently

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|| '''Slide Number 3'''
'''Learning Objectives'''
|| 
* Make a graph using script commands
* Write, edit and execute a script
* Draw a sphere
* Change the surface color of the sphere
* Generate a heat map

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|| '''Slide Number 4'''
'''System and Software Requirement'''
|| 
* '''Ubuntu Linux''' 16.04 OS
* '''Gedit''' version 3.18 and 
* '''gnuplot''' version 5.2.6

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|| '''Slide Number 5'''
'''Pre-requisites'''

'''https://spoken-tutorial.org'''
|| To follow this tutorial, 

* Learner must be familiar with basics of '''gnuplot'''. 
* For pre-requisite '''gnuplot''' tutorials, please visit this site.

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|| Press '''Ctrl+Alt+T'''.
|| Open a terminal.

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|| Type '''cd Desktop''' and press '''Enter'''.
|| Change the directory to '''Desktop'''.

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|| Type '''gnuplot''' and press '''Enter'''.
|| I will open '''gnuplot''' from '''Desktop''' directory in the '''terminal'''.

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|| Press '''Ctrl+L'''.
|| I will also clear the screen.
We will plot the function, '''cos x cos y''' to draw a surface.

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|| Type '''splot cos(x)*cos(y)''' and press '''Enter'''.
|| Enter the command '''splot space cos x times cos y'''.
The '''splot''' command generates 3D graph in the graphics window.
Make sure '''x''' and '''y''' are in parenthesis.

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|| Cursor on the graphics window.
|| The splot command generates 3d graph in the graphcis window.
Besides '''x''' and '''y''', the third axis is the value of the function in the plot.

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|| Hold down left mouse key and turn around and rotate the plot.
|| Hold down the left mouse key. 
Move the mouse to rotate the graph and change the viewing angle.

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|| Zoom into the graph.
|| Zoom in slightly into the graph to see a wavy surface.
Notice the surface is plotted in a wide mesh style.

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|| Cursor on the graphics window.
|| Let's change some of the properties of the surface.

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|| Hover mouse over the two sides of the surface.
|| We will color both sides of the surface differently.

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|| Enter the command '''set hidden3d '''.
Enter the command '''replot'''.
|| The required command for this is '''set space hidden3d''' .
Enter the command '''replot''', to see the changed colors.

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|| Show the two colors on the screen.
|| Notice the hidden surface is colored green and the top surface is purple. 

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|| Type '''set isosamples 50,50 '''and press '''Enter'''.
|| Let’s divide the surface into a fine grid.
Enter the command, '''set space isosamples space 50 comma 50'''.

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|| Type '''replot''' and press '''Enter'''.
|| '''Replot''' to notice a finer mesh defining the surface.

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|| Cursor on the graphics window.
|| Use the command, '''help space splot''' to know more about the '''splot''' command.

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|| Hold down the left mouse key and move the mouse.
|| Hold down the left mouse key and move the mouse to rotate the graph.

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|| Cursor on the view angle value, in the graphics window. 
Highlight the changed angle in the graphics window during video editing.
|| The viewing angle changes in the graphic window while rotating the graph.

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|| Close the graphic window.
|| Next, we will plot a sphere in '''gnuplot'''.
Close the graphics window.

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|| '''Slide number 6'''
'''Equation for a sphere'''

This function can be plotted in parametric mode as,
r.sin(u).cos(v), r.sin(u).sin(v),r.cos(u)
|| Equation for a sphere with radius r, centered at x0, y0, and z0 is shown here.
It is, x square plus y square plus z square is equal to r square.
This function can be plotted in parametric mode as seen here.

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|| Cursor on the slide.
|| We will write a script to draw a sphere in '''gnuplot''' using the text editor.
Then run the script file to plot a graph.

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|| Press '''Ctrl+Alt+T'''.
Type '''gedit''' and press '''Enter'''.
|| Open another '''terminal''' and type '''gedit''' to open a '''gedit''' window.

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|| Cursor on '''Gedit''' text editor.
|| '''Windows''' users may use '''notepad''' or '''wordpad''' software.

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|| Type '''# my first 3D plot''' and press '''Enter'''.
|| Let's enter a comment on the first line. 
I will type '''hash my first 3D plot''' and press '''Enter''' to start a newline.
The comments start with a '''hash'''.

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|| 
|| Next, please type the commands as shown here.

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|| Type '''set parametric''' and press '''Enter'''.
|| First, set the plot to parametric mode.

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|| Type '''set angle degree'''.
Press '''Enter'''.
|| Then set the angle to degree .

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|| Enter the 2 lines

'''set urange [0:360] '''

'''set vrange [0:180]'''

and press '''Enter'''.
|| Next, specify the ranges of parameters '''u''' and '''v'''. 

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|| Type '''set isosample 50,50''' and press '''Enter'''.
|| Set '''isosamples''' to make a fine mesh.

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|| Type '''set ticslevel 0''' and press '''Enter'''.
|| Set '''ticks''' level to zero. 
This sets the '''XY''' plane at zero value of '''Z''' axis.

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|| Type '''r=1''' and press '''Enter'''.
|| I will set the radius of the sphere to one.

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|| Type,
'''splot r*sin(u)*cos(v), r*sin(u)*sin(v),r*cos(u) '''and press '''Enter'''.
|| Next add the line, '''splot space''' and the function for sphere as seen.

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|| Press '''Ctrl+S'''.
|| Press '''Control S''' to save the file.

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|| Give file name, '''sphere.dem''' in path '''desktop''' folder.
Click on '''Save'''.
|| A dialogue box opens. 
I will save the file in '''Desktop''' folder with filename '''sphere.dem'''.
Click on '''Save''' to save the script.

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|| Minimize '''gedit''' and go to '''terminal'''.
|| Click on the hyphen sign on the top to minimize the gedit window.
Go back to the '''terminal''', where '''gnuplot''' is open.

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|| Cursor on '''terminal'''.
|| If you had closed '''gnuplot''', please open '''gnuplot''' again.
Let's run the script to generate a sphere.

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|| Enter the command '''load 'sphere.dem' '''.
|| Enter the command, '''load''' space within single quotes '''sphere dot dem'''.

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|| Point to the sphere in graphics window.
|| A sphere, centered at zero, zero, zero with radius one appears on the screen.

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|| Rotate the sphere.
|| Let’s change the color of the sphere to blue.
We will edit the script file to make the required changes.

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|| Go to the '''gedit''' script .
|| Go to the edit window to edit the script.
If you had closed it, please open the '''script''' file to edit.

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|| Add '''lc rgb 'blue'''' in the end of the splot command.
|| Add '''lc space rgb space''' within single quotes '''blue''' .
This is part of the splot command line.

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|| Press '''Ctrl+S '''.
|| Save the changes in the '''script''' file.

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|| Come back to '''gnuplot '''.
|| Come back to the '''gnuplot''' prompt and load the edited script file again.

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|| Type '''load 'sphere.dem'''' and press '''Enter'''.
|| Enter the command '''load''' space within single quotes '''sphere.dem'''.
In some systems, pressing the up arrow key scrolls through the command history.

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|| Show the blue sphere.
Notice the blue sphere in the graphics window.

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|| Cursor on the graphics window.
|| Next, let's make a '''heatmap''' with '''pm3d''' command.

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|| Select and delete the part,
'''lc rgb blue''' .
|| Go back to the script in '''gedit''' to make changes in it.
Delete the '''lc space rgb space blue''' in the splot command.

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|| Type''' with pm3d''' at the end of the same line.
|| Add, '''with space pm3d''' at the end of the line, as seen on the screen.

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|| Press '''Ctrl+S''', minimize '''gedit''' and go to '''gnuplot'''.
|| Save the '''script''' file, minimize '''gedit''' and go to '''gnuplot'''.

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|| Enter command '''load 'sphere.dem' '''.
|| Load the '''sphere.dem''' script again.

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|| Point mouse next to the map guide in graphics window. 
|| Notice the '''heatmap''' in the sphere.
The color scale bar for the color gradient, is visible on the side.

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|| Hover mouse on the range guide range.
|| This is called a '''colorbox''' in '''gnuplot'''.
The values between 1 to 0.8 are colored in yellow. 
Values between minus 0.8 to minus 1 are colored in deep purple.

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|| Cursor on the graphics window.
|| Using scripts, we can generate and make changes in the graph.

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|| Exit '''gnuplot''' and '''gedit'''.
|| Let’s exit '''gnuplot''' and '''gedit'''.
Similar scripts are available in '''gnuplot''' demo website.

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|| Cursor on the '''terminal'''.
|| Practice and familiarize with commands and styles. 
Learners can also use the help command for this purpose.

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|| Type '''q''' to quit '''gnuplot''' and close '''gedit'''.
||Let's exit '''gnuplot''' and '''gedit'''.

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|| '''Slide Number 7'''
'''Summary'''
|| To summarize, in this tutorial, we,
* Generated a 3D surface with the '''splot''' command
* Changed the viewing angle
* Modified the 3D plot
* Colored the two surfaces of the plot differently

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|| '''Slide Number 8'''
'''Summary'''
|| 
* Plotted a sphere and changed the color
* Wrote and modified a script
* Executed the script to generate a plot and 
* Learned to generate a heat map

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|| '''Slide Number 9'''
'''Assignment'''
|| For assignment, plot the following,
* Plot 5 spheres in a graph with different radius .
* Center and color the spheres differently.

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|| '''Slide Number 10'''
'''Assignment'''
Hint:
For a sphere centered at (x1,y1,z1), use the equation for sphere as seen here.

x1+r.sin(u).cos(v), y1+r.sin(u).sin(v), z1+r.cos(u)
|| For a sphere centered at (x1,y1,z1), use the equation for sphere as seen here.

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|| Show assignment screenshot.
|| Your completed assignment look similar to this.

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|| '''Slide Number 11'''
'''Spoken Tutorial Project'''
|| This video summarises the '''Spoken Tutorial Project'''.
Please download and watch it.

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|| '''Slide Number 12'''
'''Spoken Tutorial workshops'''
|| We conduct workshops and give certificates. 
For more details, please write to us.

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|| '''Slide Number 13'''
'''Forum for specific questions:'''
|| Post your timed queries in the '''forum'''.

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|| '''Slide Number 14'''
'''Acknowledgement'''
|| '''Spoken Tutorial Project''' is funded by '''MHRD''', '''Government of India'''.

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|| 
|| This is Rani from IIT Bombay. 
Thank you for joining.

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