Weather

weatherUpdate.glsl

/*[Vertex]*/
uniform float u_Gravity;
uniform float u_DeltaTime;
uniform vec3 u_MapExtents[2];
uniform sampler2D u_OverheadDepthMap;

in vec3 attr_Position;
in vec3 attr_Color;

out vec3 var_Position;
out vec3 var_Velocity;

vec3 NewParticlePosition(in float zmin, in float zmax)
{
	vec3 position = var_Position;
	position.z += (zmax - zmin);
	return position;
}

void main()
{
	var_Velocity = attr_Color;
	var_Position = attr_Position;
	var_Position.z -= 600.0 * 0.16;

	vec3 normalizedWorldPosition =
		(var_Position - u_MapExtents[0]) / (u_MapExtents[1] - u_MapExtents[0]);

	float overheadZ = 1.0 - texture(
		u_OverheadDepthMap, normalizedWorldPosition.xy).r;
	if (normalizedWorldPosition.z < overheadZ)
		var_Position = NewParticlePosition(
			u_MapExtents[0].z, u_MapExtents[1].z);
}