Merge pull request #41 from peppy/cursor-trail

Add time attribute to CursorTrail shader

osu.Game.Resources/Shaders/sh_CursorTrail.vs

@@ -1,6 +1,7 @@
 attribute vec2 m_Position;
 attribute vec4 m_Colour;
 attribute vec2 m_TexCoord;
+attribute float m_Time;
 
 varying vec2 v_DrawingPosition;
 varying vec2 v_MaskingPosition;
@@ -23,7 +24,8 @@ void main(void)
     vec3 drawingPos = g_ToDrawingSpace * vec3(m_Position, 1.0);
     v_DrawingPosition = drawingPos.xy / drawingPos.z;
 
-	v_Colour = vec4(m_Colour.rgb, clamp(m_Colour.a - g_FadeClock, 0.0, 1.0));
+    v_Colour = vec4(m_Colour.rgb, m_Colour.a * pow(clamp(m_Time - g_FadeClock, 0.0, 1.0), 1.7));
+     
     v_TexCoord = m_TexCoord;
     gl_Position = g_ProjMatrix * vec4(m_Position, 1.0, 1.0);
 }