/* This shader takes a 2D shape, puts it in 3D Object space such that is stays aligned with view,
 * and scales the shape according to per-instance attributes
 * Note that if the stiffness is zero, it assumes the scale is directly multiplied by the radius */


 #define M_PI_2     1.570796f   // pi/2

uniform mat4 ViewProjectionMatrix;
uniform vec3 screen_vecs[2];

/* ---- Instanciated Attribs ---- */
in vec2 pos;

/* ---- Per instance Attribs ---- */
in mat3x4 ScaleTranslationMatrix;
in float radius;
in vec3 color;

flat out vec4 finalColor;

void main()
{
	mat3 Scamat = mat3(ScaleTranslationMatrix);
	vec4 world_pos = vec4(
		ScaleTranslationMatrix[0][3],
		ScaleTranslationMatrix[1][3],
		ScaleTranslationMatrix[2][3],
		1.0);

	vec3 screen_pos = screen_vecs[0].xyz * pos.x + screen_vecs[1].xyz * pos.y;
	world_pos.xyz += Scamat * (screen_pos * radius);

	gl_Position = ViewProjectionMatrix * world_pos;
	finalColor = vec4(color, 1.0);
}