1.add DrawRect2D.vert/.geom shaders

2.add AlphaMask.frag shader

shader/AlphaMask.frag

@@ -0,0 +1,16 @@
+#version 450 core
+
+layout(binding = 2) uniform sampler2D tex;
+
+layout(location = 0) in vec2 FragmentTexCoord;
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    vec4 color=texture(tex,FragmentTexCoord);
+
+    if(color.a<0.3)
+        discard;
+
+    FragColor=vec4(color.rgb,1);
+}