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#version 140
#extension GL_ARB_explicit_attrib_location : require
uniform float deltaT;
layout (location = 0) in vec4 in_position;
out vec4 next_position;
const float PI = 3.1415926535897932384626433832795;
const vec2 origin = vec2(0.5, 0.5);
float getTheta(in vec2 position)
{
if (position.x == 0.0)
{
return position.y > 0.0 ? PI / 2.0 : (position.y < 0.0 ? -PI / 2.0 : 0.0);
}
return atan(position.y, position.x);
}
void main()
{
float r = length(in_position.xy - origin);
float theta = getTheta(in_position.xy - origin);
theta += PI * deltaT / 2.0;
if (true)
{
next_position = vec4(
origin.x + r*cos(theta),
origin.y + r*sin(theta),
0.0,
1.0
);
}
else
{
next_position = in_position;
}
}
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