Add texture drawing on texture mapping edit mode and semi-transparent projection mapped surface over it

example/src/ofApp.cpp

@@ -30,7 +30,27 @@ void ofApp::update()
 
 void ofApp::draw()
 {
+    // Check GUI mode - we want to see the texture that we are editing
+    // together with the actual surface being projection mapped.
+    
+    ofxSurfaceGui::editMode mode = gui.getMode();
+    if ( mode == ofxSurfaceGui::TEXTURE_MAPPING ) {
+        // Draw texture of the surface in the background
+        //triangleSurface.getTexture()->draw(ofPoint(0,0));
+        triangleSurface.drawTexture(ofVec2f(0, 0));
+        
+        // Make the triangle surface transparent but still visible
+        // while we map the texture coordinates.
+        ofPushStyle();
+        ofSetColor(255, 255, 255, 200);
+    }
+    
     triangleSurface.draw();
+    
+    if ( mode == ofxSurfaceGui::TEXTURE_MAPPING ) {
+        ofPopStyle();
+    }
+    
     gui.draw();
 }
 

src/ofxBaseSurface.cpp

@@ -38,6 +38,24 @@ void ofxBaseSurface::createDefaultTexture()
     texture = &defaultTexture;
 }
 
+void  ofxBaseSurface::drawTexture(ofVec2f position)
+{
+    ofMesh texMesh;
+    texMesh.addVertex(position);
+    texMesh.addVertex(position + ofVec2f(texture->getWidth(), 0.0f));
+    texMesh.addVertex(position + ofVec2f(texture->getWidth(), texture->getHeight()));
+    texMesh.addVertex(position + ofVec2f(0.0f, texture->getHeight()));
+    texMesh.addTriangle(0, 2, 3);
+    texMesh.addTriangle(0, 1, 2);
+    texMesh.addTexCoord(ofVec2f(0.0f, 0.0f));
+    texMesh.addTexCoord(ofVec2f(1.0f, 0.0f));
+    texMesh.addTexCoord(ofVec2f(1.0f, 1.0f));
+    texMesh.addTexCoord(ofVec2f(0.0f, 1.0f));
+    texture->bind();
+    texMesh.draw();
+    texture->unbind();
+}
+
 ofTexture* ofxBaseSurface::getTexture()
 {
     return texture;

src/ofxBaseSurface.h

@@ -12,6 +12,9 @@ public:
     virtual void setVertex(int index, ofVec2f p){};
     virtual void setTexCoord(int index, ofVec2f t){};
     
+    // Draws a texture using ofMesh
+    void drawTexture(ofVec2f position);
+    
     ofTexture* getTexture();
     
 protected: