README
¶
package dieselfluid/atmosphere
package Atmosphere
This package allows you to create atmospheric renders with approximations for latitudes and longitudes and times of the year. Using a global decimal UTC time system. Setting the Standard Meridian offsets the decimal time rotation and allows you to work in local time.
Note: Atmosphere package assumes to be working in meters to include all physical phenomena including wavelengths astronomical measurements
Coefficients are based off of the surface layer coefficients for Rayleigh and Mie scattering phenomena future work can be done to move non normalized images into an HDR format for Global Environmental lights.
We can also extend the framework for atmosphere into a more generalized Rayleigh/Mie Scatter framework to allow for different Mie Scattering solutions during weather environmental changes and descriptions
This framework in the future should be updated to incorporate a handler for Electron Node dispatch requests
Include options for detailed Rayleight / Mie Scatter and height configurations for complete control over the model for users to include all configurable options
Usage
Create a new atmosphere object and create textures
mSky := NewAtmosphere(45.0, 0.0)
mSky.SetDay(200.2)
base := "sky_"
for i := 0; i < 10; i++ {
filename := base + strconv.FormatInt(int64(i), 10) + ".png"
mSky.StepDay(1 + float32(i)/10)
mSky.CreateTexture(256, 256, filename)
}
Notes
- Next update will fix the celestial observer model.
- Fixed Mie Scattering Error where sun disk failed to render
- Adjust Sky.Light.Lx.Flux settings for sun intensity. Default (20.5)
- Adjust Mie Scattering Phase Function by tuning g variable, forward scatter coefficient
- BetaR , BetaM correspond to the extinction coefficients in RGB tristimulus color space. Tune these vectors according to atmopsheric composition to affect atmospheric colors
Todo
- Eliminate Negative View Vector Evaluations
- Faciliate Parameter Tuning for the Atmosphere Package as a whole with JSON Configurations
- Approximate depth integrals for Rayleigh Mie scattering with Pre-Packaged LUTs for algorithmic speedup
- Implement Volumetric Cloud Features
- Implement Ozone Extinction
Table of Measurements
| phenomena | description | units | underlying units |
|---|---|---|---|
| Flux | Radiant Flux | Watts | kg m^2 s^-3 |
| Wavelength | Electromagnetic Wavelength | Meters | m |
| Astronomical Units | Radii | Meters | m |
Documentation
¶
Index ¶
- Constants
- func ImageFromPixels(pixels []vector.Vec, width int, height int, clamp bool, alpha uint8, ...)
- type Atmosphere
- func (sky *Atmosphere) ComputeAtmosphere(uSampleDomain int, vSampleDomain int) []vector.Vec
- func (sky *Atmosphere) ComputeRegion(uSampleDomain int, vSampleDomain int, x_corner int, y_corner int, width int, ...) []vector.Vec
- func (sky *Atmosphere) CreateEnvBox(width int, height int, clamp bool)
- func (sky *Atmosphere) CreateTexture(width int, height int, clamp bool, filename string)
- func (sky *Atmosphere) InitPosition(absDay float32, inclinationOffset float32) error
- func (sky *Atmosphere) UpdatePosition(delta float32) error
- func (sky *Atmosphere) VolumetricScatterRay(sample vector.Vec, view vector.Vec) vector.Vec
- type Domain
- type EarthCoords
Constants ¶
const ( PI = 3.141529 AXIAL_TILT = 23.5 //Degrees RAYLEIGH_SAMPLES = 25 //RAYLEIGH sampling LIGHT_PATH_SAMPLES = 25 //PATH SAMPLES AU = 150000000 //SUN HM = 1500 //AEROSOL MIE SCATTER HEIGHT HR = 8000 //RAYLEIGH SCATTER HEIGHT )
Atmosphere environment lighting model.
This model generates a sun position based on lat/long and solar times and then we simulate atmospheric scattering processes via Rayleigh/Mie Scattering.
const (
EARTH_RAD = 6370
)
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Atmosphere ¶
type Atmosphere struct {
Light light.Light
Spd light.Spectrum
Sun polar.Polar //Orbtial Solar System Earth 2 Sun Polar Coordinate
Earth *EarthCoords
Day float32
Dir vector.Vec //Euclidian Sun Direction
}
Atmosphere Environment
func NewAtmosphere ¶
func NewAtmosphere(lat float32, long float32) *Atmosphere
Allocates Default Data Structure and Solar Coords Structs
func (*Atmosphere) ComputeAtmosphere ¶
func (sky *Atmosphere) ComputeAtmosphere(uSampleDomain int, vSampleDomain int) []vector.Vec
Maps texel coordinates to spherical coordinate sampler values (-1,1) and stores resultant map in single texture.
func (*Atmosphere) ComputeRegion ¶
func (sky *Atmosphere) ComputeRegion(uSampleDomain int, vSampleDomain int, x_corner int, y_corner int, width int, height int) []vector.Vec
Maps texel coordinates to spherical coordinate sampler values (-1,1) and stores
func (*Atmosphere) CreateEnvBox ¶
func (sky *Atmosphere) CreateEnvBox(width int, height int, clamp bool)
Creates 6-textures from from computed atmosphere, non-clamping allows for HDR storage width and height are the per texture width height values of the image size
func (*Atmosphere) CreateTexture ¶
func (sky *Atmosphere) CreateTexture(width int, height int, clamp bool, filename string)
Creates texture from from computed atmosphere, non-clamping allows for HDR storage
func (*Atmosphere) InitPosition ¶
func (sky *Atmosphere) InitPosition(absDay float32, inclinationOffset float32) error
Initialize sun positional reference coordinates in terms of polar coordinates
func (*Atmosphere) UpdatePosition ¶
func (sky *Atmosphere) UpdatePosition(delta float32) error
Updates sun positional coordinates by rotating Azimuth & Polar coords by delta degrees
func (*Atmosphere) VolumetricScatterRay ¶
Given a sampling vector and a viewing direction calculate RGB stimulus return Based on the Attenuation/Mie Phase Scatter/RayleighScatter Terms
type EarthCoords ¶
type EarthCoords struct {
Latitude float32 //Decimal Lat
Longitude float32 //Decimal Long
PolarCoord polar.Polar //Polar Axis offset
StandardMeridian float32 //Longitude Standard Meridian For Local Time Offsets
DomainOffset [2]float32 //Domain offsets for polar sampling of sky depths
GreaterSphere polar.Polar //Atmospheric Polar Parameters Polar Parameters
}
Earth Coordinates and Greater Earth will not be rotated for simplicity all Polar transformations are added to sun Polar coordinates as negative transforms
func NewEarth ¶
func NewEarth(lat float32, long float32) *EarthCoords
Declare New Sun Environment with Standard Merdian time set for NYC - Sky Functions handle sun rotation
func (*EarthCoords) GetPosition ¶
func (earth *EarthCoords) GetPosition() vector.Vec
func (*EarthCoords) GetRadius ¶
func (earth *EarthCoords) GetRadius() float32
func (*EarthCoords) GetSample ¶
func (earth *EarthCoords) GetSample(uv [2]float32) vector.Vec
Takes clamped [U,V] polar coordinates from [-1,1.0] and returns the ray depth Returns vector with magnitude to fixed point in sky in valid coordinates
func (*EarthCoords) GetSampleDepth ¶
func (earth *EarthCoords) GetSampleDepth(sample vector.Vec) float32
Approximation of sample depth based on Z coordinate
Source Files