add possibility to generate FBO with texture

The caller is responsible to delete the buffers. Depending on bRenderbuffer either with glDeleteRenderbuffers or with glDeleteTextures.

Change-Id: I5ccbd49862c381abf04e812765cced485a083f89

include/vcl/opengl/OpenGLHelper.hxx

@@ -30,9 +30,11 @@ public:
     /**
      * The caller is responsible for deleting the buffer objects identified by
      * nFramebufferId, nRenderbufferDepthId and nRenderbufferColorId
+     * @param bRenderbuffer true => off-screen rendering, false => rendering to texture
+     *          This also affects whether to free with glDeleteRenderbuffers or glDeleteTextures
      */
-    static void createFramebuffer(long nWidth, long nHeight,
-            GLuint& nFramebufferId, GLuint& nRenderbufferTextId, GLuint& nRenderbufferColorId);
+    static void createFramebuffer(long nWidth, long nHeight, GLuint& nFramebufferId,
+            GLuint& nRenderbufferTextId, GLuint& nRenderbufferColorId, bool bRenderbuffer = true);
 
     // Get OpenGL version (needs a context)
     static float getGLVersion();

vcl/source/opengl/OpenGLHelper.cxx

@@ -275,8 +275,8 @@ std::ostream& operator<<(std::ostream& rStrm, const glm::mat4& rMatrix)
     return rStrm;
 }
 
-void OpenGLHelper::createFramebuffer(long nWidth, long nHeight,
-        GLuint& nFramebufferId, GLuint& nRenderbufferDepthId, GLuint& nRenderbufferColorId)
+void OpenGLHelper::createFramebuffer(long nWidth, long nHeight, GLuint& nFramebufferId,
+        GLuint& nRenderbufferDepthId, GLuint& nRenderbufferColorId, bool bRenderbuffer)
 {
     // create a renderbuffer for depth attachment
     glGenRenderbuffers(1, &nRenderbufferDepthId);
@@ -284,13 +284,31 @@ void OpenGLHelper::createFramebuffer(long nWidth, long nHeight,
     glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, nWidth, nHeight);
     glBindRenderbuffer(GL_RENDERBUFFER, 0);
 
-    // create a renderbuffer for color attachment
-    glGenRenderbuffers(1, &nRenderbufferColorId);
-    glBindRenderbuffer(GL_RENDERBUFFER, nRenderbufferColorId);
-    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8, nWidth, nHeight);
-    glBindRenderbuffer(GL_RENDERBUFFER, 0);
+    if(bRenderbuffer)
+    {
+        // create a renderbuffer for color attachment
+        glGenRenderbuffers(1, &nRenderbufferColorId);
+        glBindRenderbuffer(GL_RENDERBUFFER, nRenderbufferColorId);
+        glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8, nWidth, nHeight);
+        glBindRenderbuffer(GL_RENDERBUFFER, 0);
+    }
+    else
+    {
+        glGenTextures(1, &nRenderbufferColorId);
+        glBindTexture(GL_TEXTURE_2D, nRenderbufferColorId);
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, nWidth, nHeight, 0,
+                             GL_RGBA, GL_UNSIGNED_BYTE, 0);
+        glBindTexture(GL_TEXTURE_2D, 0);
+
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                GL_TEXTURE_2D, nRenderbufferColorId, 0);
+    }
 
-    // create a framebuffer object and attach renderbuffer and texture
+    // create a framebuffer object and attach renderbuffer
     glGenFramebuffers(1, &nFramebufferId);
     glCheckFramebufferStatus(GL_FRAMEBUFFER);
     glBindFramebuffer(GL_FRAMEBUFFER, nFramebufferId);