Lens-effect

Pseudo Lens flare effect for 2D video game

PROJECT:

Lens flare effect demonstration is using a wavelength to RGB algorithm written in python and ported into C language for speed improvement. You can find the wavelength to RGB algorithm in the C file wavelength.c under the main project directory.

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TECHNIQUE:

1) A vector direction is calculated from the mouse cursor position on the screen 
   relative to the centre of the flare effect. 
   
2) Polygons of various sizes and colors are added along that vector (with sizes 
   proportional to the distance from the centre of the effect).
   
3) All polygons are filled with RGB color corresponding to the wavelength relative to
   their distances from the centre of the effect
   
Polygons colors will vary from purple to red (see color spectrum below), red for polygon close to the observer
and purple toward the centre/origin of the lens flare effect.

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DEMO:

Download the source code and decompress the archive Lens-effect-master.

Enter the folder Lens-effect-master (and run the following command in a DOS command prompt)

C:>python setup_project.py build_ext --inplace

Edit the file test_flares.py in your favorite python IDE and run it

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Color Spectrum

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HOW TO CREATE FLARES

The project is using the game library Pygame for loading image, transformation and creating sprites

1) Create a texture

TEXTURE = pygame.image.load('Assets\\Untitled3.png').convert(24)
TEXTURE = pygame.transform.smoothscale(TEXTURE, (100, 100))
TEXTURE.set_colorkey((0, 0, 0, 0), pygame.RLEACCEL) 

2) Create a polygon

octagon = polygon()

3) Instantiate the flares

In the below example, we are creating 20 sub-flares from the texture Untitled3.png

All instances will be added to the python list FLARES.

The method second_flares assign the texture and give a random position to the flare along the direction vector.

Float values 0.8 and 1.2 are the minimum and maximum for the polygon size.

Texture(s) belonging to the list exc (exclude) will be blit directly on the flare vector without creating a textured polygon

for r in range(20):
    FLARES.append(second_flares(TEXTURE, octagon.copy(),
                                make_vector2d(FLARE_EFFECT_CENTRE), 0.8, 1.2, exc))

4) Create the sprites

for flares in FLARES:
    create_flare_sprite(
        images_=flares[0], distance_=flares[1], vector_=VECTOR,
        position_=FLARE_EFFECT_CENTRE, layer_=0, gl_=GL,
        child_group_=CHILD, blend_=pygame.BLEND_RGB_ADD, event_type='CHILD', delete_=False)

# flares[0] : Correspond to the texture 
# flares[1] : Distance from the centre of the effect
# vector    : Flare vector
# position  : Polygon(s) positions (x,y) along the flare vector
# layer     : Sprite layer used for displaying the sprite(s) (this is not implemented yet)
# GL        : Global constant (python class containing all the project constants and variables)
# CHILD     : is the group containing all the instances
# blend     : Sprite additive mode (e.g BLEND_RGB_ADD etc)
# event     : Event can be set to 'CHILD' or 'PARENT' child is used for the flares (polygons)
#             Child polygon 's size is inalterable. 

5) Display the sprites in your game mainloop

display_flare_sprite(CHILD, STAR_BURST, STAR_BURST3x, GL, VECTOR)

REQUIREMENTS:

- python > 3.0
- numpy 
- pygame 
- Cython
- A compiler such visual studio, MSVC, CGYWIN setup correctly on your system

BUILDING THE PROJECT:

Use the following command:
C:\python setup_project.py build_ext --inplace

Reference

see page: http://www.physics.sfasu.edu/astro/color/spectra.html

Wavelength to RGB in Python - Noah.org
Based on code by Dan Bruton

== A few notes about color ==

    Color   Wavelength(nm) Frequency(THz)
    Red     620-750        484-400
    Orange  590-620        508-484
    Yellow  570-590        526-508
    Green   495-570        606-526
    Blue    450-495        668-606
    Violet  380-450        789-668

    f is frequency (cycles per second)
    l (lambda) is wavelength (meters per cycle)
    e is energy (Joules)
    h (Plank's constant) = 6.6260695729 x 10^-34 Joule*seconds
                         = 6.6260695729 x 10^-34 m^2*kg/seconds
    c = 299792458 meters per second
    f = c/l
    l = c/f
    e = h*f
    e = c*h/l

    List of peak frequency responses for each type of 
    photoreceptor cell in the human eye:
        S cone: 437 nm
        M cone: 533 nm
        L cone: 564 nm
        rod:    550 nm in bright daylight, 498 nm when dark adapted. 
                Rods adapt to low light conditions by becoming more sensitive.
                Peak frequency response shifts to 498 nm.