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1
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- CS248 Help Session #1
- Original slides by Georg Petschnigg
- Modified by: Sean Walker, Rene Patnode
- Stanford University
- October 6, 2004
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2
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- Getting Started
- Assignment Discussion
- Overpainting Brush
- Tinting Brush
- Brush Visualization
- Grading Details
- Extra Credit
- Questions
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3
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- Read assignment carefully and pay attention to the details.
- Go to help session
- Familiarize yourself with Raptor/Firebird Lab Located in the Basement of
Sweet Hall
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4
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- Ways to work with TA Support
- Go to Sweet Hall (Best Way – 5 Minutes)
- Work Remotely (Good Way – 5 Minutes)
- Ways to work without TA support
- Reproduce Sweet Hall Lab development environment on you own Machine (1
Hour)
- Your code still has to work on the Sweet Hall machines (more risk for
you)
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5
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- Pick a free computer, Log on
- Copy assignment from /usr/class/cs248/assignments/assignment1/
to local directory
- Run ‘make’
- Run ‘./paint.i386-linux’
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6
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- ssh to firebird, raptor or leland (make sure
- X-tunneling is enabled)
- Export the display (using e.g. Exceed3D)
- Follow instructions on previous slide
- >ssh
raptor.stanford.edu
>setenv DISPLAY yourIP:0.0
>xterm &
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7
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- You are going to write a paint program
- Teaches you 2D Raster Graphics
- Visualize concepts learned in Class (Brushes, HSV)
- Be creative with extra credit
- The next slides follow the Assignment (Handout #3) step by step
- Reminder: Read the assignment
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8
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9
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- Rectangular Overpainting Brush
- Like Microsoft Paint or “Pencil Tool” in PhotoShop
- Color Picker for RGB, HSV
- See http://java.sun.com/docs/books/tutorial/uiswing/
components/colorchooser.html or any
- commercial paint program
- Value (1.0 bright, 0.0 black)
- Saturation
(1.0 strong hue, 0.0
faded hue)
- Size Control for Brush
Demo: Painting, Picking Colors in PaintShop Pro 7
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10
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11
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- Once you are done with Part 1 you should be able to draw some basic
images
- Notice the hard edges and jaggies around the stroke… this is what Part 2
will fix
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12
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- Implement Weighted Mask Driven Brush as described in Handout #4
- Instead of a rectangular brush, have it gently “blend” to its
surroundings. Use HSV interpolation
- Checkboxes for interpolating along H,S,V axis
- Allow all permutations HSV, HS, HV, SV, H, S, V
- Choose a mask function and give user control over it
- Make sure it gradually falls off to zero at edges!
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13
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- Like painting with partially transparent paint. Commonly referred to as
“alpha” blending.
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14
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- Lookup array determines how each pixel in the brush is affected.
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15
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- Mask contains alpha/weight for each pixel in brush
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16
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17
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18
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19
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- Interpolating half way between Red and Cyan (a = 0.5)
- NewColor = 0.5 Cyan + 0.5 Red
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20
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- Choose which HSV components to affect.
- Allow for any combination.
- if (H_check) NewH = (1-a) CH + a PaintH
- else NewH = CH;
- if (S_check) NewS = (1-a) CS + a PaintS
- else NewS = CS;
- if (V_check) NewV = (1-a) CV + a PaintV
- else NewV = CV;
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21
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22
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- Brush Visualization should tell user what its color, falloff and size is
- Brush should always be visible regardless of color
- Draw 1x (actual size) and 4x (four times larger in x and y) versions of
the brush
- Make the larger version discretized – that is it should be a
choppy/chunky/pixel replicated version of the actual brush (think xmag,
snoop)
- Make sure this visualization will help you explain to user, TAs,
Professor and yourself how the brush weights affect drawing
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23
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- Correctness (40%)
- Don’t crash
- Implement all required features
- (Read the directions like a lawyer)
- Efficiency (20 %)
- No noticeable lag while using your application
- User Interface (20%)
- Programming Style (20%)
- Copying code (Don’t do it)
- Submitting with ‘/usr/class/cs248/bin/submit’
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24
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25
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- Ask now
- Come to Office Hours
- Email: cs248-aut0405-tas@lists.stanford.edu
- Remember: Computer Graphics is fun - if you are not having fun ask TAs
for help
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Notes
