diff --git a/src/rtt.cpp b/src/rtt.cpp
index 0b91f31..6d6fbba 100644
--- a/src/rtt.cpp
+++ b/src/rtt.cpp
@@ -98,16 +98,18 @@ void RTT::copy(const RTT & source)
 {
     App::I->render_task([&]
     {
-        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &oldDFboID);
-        glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &oldRFboID);
+        GLint old_draw = 0;
+        GLint old_read = 0;
+        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &old_draw);
+        glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &old_read);
 
         glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboID);
         glBindFramebuffer(GL_READ_FRAMEBUFFER, source.fboID);
         glBlitFramebuffer(0, 0, source.w, source.h, 0, 0, w, h, 
             GL_COLOR_BUFFER_BIT, GL_LINEAR);
 
-        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, oldDFboID);
-        glBindFramebuffer(GL_READ_FRAMEBUFFER, oldRFboID);
+        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, old_draw);
+        glBindFramebuffer(GL_READ_FRAMEBUFFER, old_read);
     });
 }
 
@@ -117,16 +119,18 @@ void RTT::copy(const RTT& source, const glm::vec4& rect)
     {
         auto r = rect_intersection(rect, { 0, 0, w, h });
 
-        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &oldDFboID);
-        glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &oldRFboID);
+        GLint old_draw = 0;
+        GLint old_read = 0;
+        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &old_draw);
+        glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, &old_read);
 
         glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboID);
         glBindFramebuffer(GL_READ_FRAMEBUFFER, source.fboID);
         glBlitFramebuffer(r.x, r.y, r.z, r.w, r.x, r.y, r.z, r.w, 
             GL_COLOR_BUFFER_BIT, GL_NEAREST);
 
-        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, oldDFboID);
-        glBindFramebuffer(GL_READ_FRAMEBUFFER, oldRFboID);
+        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, old_draw);
+        glBindFramebuffer(GL_READ_FRAMEBUFFER, old_read);
     });
 }
 
@@ -251,6 +255,21 @@ void RTT::clear(glm::vec4 color)
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 }
 
+void RTT::clear_mask(glm::bool4 mask, glm::vec4 color)
+{
+    // save old state
+    std::array<GLboolean, 4> old_mask;
+    glGetBooleanv(GL_COLOR_WRITEMASK, std::data(old_mask));
+
+    // clear with mask
+    glColorMask(mask.r, mask.g, mask.b, mask.a);
+    glClearColor(color.r, color.g, color.b, color.a);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    // restore old state
+    glColorMask(old_mask[0], old_mask[1], old_mask[2], old_mask[3]);
+}
+
 glm::ivec4 RTT::calc_bounds()
 {
     auto data = std::unique_ptr<glm::u8vec4[]>(reinterpret_cast<glm::u8vec4*>(readTextureData()));
diff --git a/src/rtt.h b/src/rtt.h
index 80cfcc0..e17405f 100644
--- a/src/rtt.h
+++ b/src/rtt.h
@@ -27,6 +27,7 @@ public:
     bool create(int width, int height, int tex = -1, GLint internal_format = GL_RGBA8, bool depth_buffer = false);
     bool recreate() { return create(w, h); }
     void clear(glm::vec4 color = glm::vec4(0));
+    void clear_mask(glm::bool4 mask, glm::vec4 color = glm::vec4(0));
     glm::ivec4 calc_bounds();
     uint8_t* readTextureData(uint8_t* buffer = nullptr);
     float* readTextureDataFloat(float* buffer = nullptr);