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// Earth vertex shader computes lighting coefficients.
//
// Note: For optimal light animation set the RenderMonkey cycle time 
// for predefined variables to 20 seconds.  (Found in the Edit->Preferences).

// predefined variables used to animate light direction
uniform float cos_time_0_2PI, sin_time_0_2PI;

// artist variable to control season
uniform float season;

// varying variables passed to fragment shader
varying float Diffuse;
varying vec3  Specular;
varying vec2  TexCoord;

void main(void)
{
    // calculate vertex position in eye coordinates
    vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;
    
    // compute the transformed normal
    vec3 tnorm      = normalize(gl_NormalMatrix * gl_Normal);

    // compute the light vector pointing toward the sun, in model coordinates
    // x,y compose the longitude and z the (seasonal) lattitude of the nadir point.
    vec3 lightVec = normalize(gl_NormalMatrix * vec3(cos_time_0_2PI, season,sin_time_0_2PI));

    // compute the reflection vector
    vec3 reflectVec = reflect(-lightVec, tnorm);
    
    // compute a unit vector in direction of viewing position
    vec3 viewVec    = normalize(vec3 (-ecPosition));

    // Calculate specular light intensity, scale down and
    // apply a slightly yellowish tint. 
    float specIntensity = pow(max(dot(reflectVec, viewVec), 0.0), 8.0);
    specIntensity       = 0.3 * specIntensity; 
    Specular            = specIntensity * vec3 (1.0, 0.941, 0.898);
    
    // Calculate a diffuse light intensity
    Diffuse             = dot(lightVec, tnorm);

    // Pass texture coordinates fragment shader
    TexCoord    = vec2 (gl_MultiTexCoord0);
    TexCoord.x  = TexCoord.x;
    
    // output final vertex information
    gl_Position     = gl_ModelViewProjectionMatrix * gl_Vertex;
}

Code: Select all

// Earth fragment shader blends day/night/cloud/gloss textures based on local time of day.

uniform sampler2D EarthDay, EarthNight, EarthCloudGloss;
uniform bool cloudCover;

varying float Diffuse;
varying vec3  Specular;
varying vec2  TexCoord;

const float Terminator = 0.3;
const float InvTerminator = 1.0 / (2.0 * Terminator);

void main (void)
{
    // separate maps are packed into the color components of this texture
    // clouds.r = cloud opacity
    // clouds.g = water glossiness
    vec2  cg     = texture2D(EarthCloudGloss, TexCoord).rg;
    float clouds = cg.r * float(cloudCover);
    float gloss  = cg.g;

    // load daytime color, plus a specular component modulated by the gloss map  
    vec3 daytime   = texture2D(EarthDay, TexCoord).rgb * Diffuse + Specular * gloss;
    
    // mix in diffusely-lit clouds, modulated by the cloud opacity
    daytime = mix(daytime, vec3(abs(Diffuse)), clouds);

    // load night image, modulated by cloud opacity
    vec3 nighttime = texture2D(EarthNight, TexCoord).rgb * (1.0 - clouds);

    // assume day, to start
    vec3 color = daytime;
 
    // if fully dark, select night
    if (Diffuse < -Terminator)
    {
        color = nighttime;
    }

    // within the twilight zone, mix night/day
    if (abs(Diffuse) < Terminator )
    {
        color = mix(nighttime, daytime, (Diffuse + Terminator) * InvTerminator);
    }
    
    gl_FragColor = vec4 (color, 1.0);
}

Code: Select all

material Earth
{
	technique
	{
		pass
		{

			texture_unit
			{
				texture Earth.jpg
				texture EarthNight.jpg
				texture EarthClouds.jpg
			}
		}
	}
}