libgui|GLFramebuffer: Stereo left/right swap mode

Even though rendering always happens in Canvas’s GL frame buffer, VR mode 13 should now theoretically work as GLFramebuffer can be told to use a different swap mode for the left/right frames. In practice, the “left” swap mode draws the contents of the Canvas frame buffer into the window’s BACK_LEFT buffer; same goes for the “right” swap mode. The “stereo” swap will then simply do a regular back-to-front swap with the finished contents.
skyjake · Dec 16, 2013 · ff52397 · ff52397
1 parent 771e85b
commit ff52397
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Showing 6 changed files with 111 additions and 51 deletions.
diff --git a/doomsday/libgui/include/de/gui/canvas.h b/doomsday/libgui/include/de/gui/canvas.h
@@ -28,6 +28,7 @@
 #include "../KeyEventSource"
 #include "../MouseEventSource"
 #include "../GLTarget"
+#include "../GLFramebuffer"
 
 namespace de {
 
@@ -160,10 +161,12 @@ class LIBGUI_PUBLIC Canvas : public QGLWidget, public KeyEventSource, public Mou
      */
     GLTarget &renderTarget() const;
 
+    GLFramebuffer &framebuffer();
+
     /**
      * Copies or swaps the back buffer to the front, making it visible.
      */
-    void swapBuffers();
+    void swapBuffers(gl::SwapBufferMode swapMode = gl::SwapMonoBuffer);
 
 protected:
     void initializeGL();

diff --git a/doomsday/libgui/include/de/gui/canvaswindow.h b/doomsday/libgui/include/de/gui/canvaswindow.h
@@ -27,6 +27,8 @@
 #include <de/Rectangle>
 #include <de/NativePath>
 
+#include "../GLFramebuffer"
+
 #ifdef WIN32
 #  undef min
 #  undef max
@@ -147,7 +149,7 @@ class LIBGUI_PUBLIC CanvasWindow : public QMainWindow,
      */
     bool grabToFile(NativePath const &path) const;
 
-    void swapBuffers() const;
+    void swapBuffers(gl::SwapBufferMode swapMode = gl::SwapMonoBuffer) const;
 
     /**
      * Activates the window's GL context so that OpenGL API calls can be made.

diff --git a/doomsday/libgui/include/de/gui/glframebuffer.h b/doomsday/libgui/include/de/gui/glframebuffer.h
@@ -28,6 +28,15 @@
 
 namespace de {
 
+namespace gl {
+    enum SwapBufferMode {
+        SwapMonoBuffer,
+        SwapStereoLeftBuffer,
+        SwapStereoRightBuffer,
+        SwapStereoBuffers
+    };
+}
+
 class Canvas;
 
 /**
@@ -70,7 +79,16 @@ class LIBGUI_PUBLIC GLFramebuffer : public Asset
     GLTexture &colorTexture() const;
     GLTexture &depthStencilTexture() const;
 
-    void swapBuffers(Canvas &canvas);
+    /**
+     * Swaps buffers.
+     *
+     * @param canvas    Canvas where to swap.
+     * @param swapMode  Stereo swapping mode:
+     *      - gl::SwapMonoBuffer: swap is done normally into the Canvas's framebuffer
+     *      - gl::SwapStereoLeftBuffer: swap updates the back/left stereo buffer
+     *      - gl::SwapStereoRightBuffer: swap updates the back/right stereo buffer
+     */
+    void swapBuffers(Canvas &canvas, gl::SwapBufferMode swapMode = gl::SwapMonoBuffer);
 
 public:
     /**

diff --git a/doomsday/libgui/src/canvas.cpp b/doomsday/libgui/src/canvas.cpp
@@ -200,10 +200,16 @@ DENG2_PIMPL(Canvas)
         framebuf.glDeinit();
     }
 
-    void swapBuffers()
+    void swapBuffers(gl::SwapBufferMode mode)
     {
+        if(mode == gl::SwapStereoBuffers && !self.format().stereo())
+        {
+            // The canvas is not using a stereo format, must do a normal swap.
+            mode = gl::SwapMonoBuffer;
+        }
+
         /// @todo Double buffering is not really needed in manual FB mode.
-        framebuf.swapBuffers(self);
+        framebuf.swapBuffers(self, mode);
     }
 };
 
@@ -306,9 +312,14 @@ GLTarget &Canvas::renderTarget() const
     return d->framebuf.target();
 }
 
-void Canvas::swapBuffers()
+GLFramebuffer &Canvas::framebuffer()
+{
+    return d->framebuf;
+}
+
+void Canvas::swapBuffers(gl::SwapBufferMode swapMode)
 {
-    d->swapBuffers();
+    d->swapBuffers(swapMode);
 }
 
 void Canvas::initializeGL()

diff --git a/doomsday/libgui/src/canvaswindow.cpp b/doomsday/libgui/src/canvaswindow.cpp
@@ -246,10 +246,10 @@ bool CanvasWindow::grabToFile(NativePath const &path) const
     return d->canvas->grabImage().save(path.toString());
 }
 
-void CanvasWindow::swapBuffers() const
+void CanvasWindow::swapBuffers(gl::SwapBufferMode swapMode) const
 {
     // Force a swapbuffers right now.
-    d->canvas->swapBuffers();
+    d->canvas->swapBuffers(swapMode);
 }
 
 void CanvasWindow::glActivate()

diff --git a/doomsday/libgui/src/glframebuffer.cpp b/doomsday/libgui/src/glframebuffer.cpp
@@ -96,34 +96,31 @@ DENG2_PIMPL(GLFramebuffer)
 
     void alloc()
     {
-        if(!GLInfo::extensions().EXT_framebuffer_blit)
-        {
-            // Prepare the fallback blit method.
-            VBuf *buf = new VBuf;
-            bufSwap.addBuffer(buf);
-            bufSwap.program().build(// Vertex shader:
-                                    Block("uniform highp mat4 uMvpMatrix; "
-                                          "attribute highp vec4 aVertex; "
-                                          "attribute highp vec2 aUV; "
-                                          "varying highp vec2 vUV; "
-                                          "void main(void) {"
-                                              "gl_Position = uMvpMatrix * aVertex; "
-                                              "vUV = aUV; }"),
-                                    // Fragment shader:
-                                    Block("uniform sampler2D uTex; "
-                                          "varying highp vec2 vUV; "
-                                          "void main(void) { "
-                                              "gl_FragColor = texture2D(uTex, vUV); }"))
-                    << uMvpMatrix
-                    << uBufTex;
-
-            buf->setVertices(gl::TriangleStrip,
-                             VBuf::Builder().makeQuad(Rectanglef(0, 0, 1, 1), Rectanglef(0, 1, 1, -1)),
-                             gl::Static);
-
-            uMvpMatrix = Matrix4f::ortho(0, 1, 0, 1);
-            uBufTex = color;
-        }
+        // Prepare the fallback blit method.
+        VBuf *buf = new VBuf;
+        bufSwap.addBuffer(buf);
+        bufSwap.program().build(// Vertex shader:
+                                Block("uniform highp mat4 uMvpMatrix; "
+                                      "attribute highp vec4 aVertex; "
+                                      "attribute highp vec2 aUV; "
+                                      "varying highp vec2 vUV; "
+                                      "void main(void) {"
+                                          "gl_Position = uMvpMatrix * aVertex; "
+                                          "vUV = aUV; }"),
+                                // Fragment shader:
+                                Block("uniform sampler2D uTex; "
+                                      "varying highp vec2 vUV; "
+                                      "void main(void) { "
+                                          "gl_FragColor = texture2D(uTex, vUV); }"))
+                << uMvpMatrix
+                << uBufTex;
+
+        buf->setVertices(gl::TriangleStrip,
+                         VBuf::Builder().makeQuad(Rectanglef(0, 0, 1, 1), Rectanglef(0, 1, 1, -1)),
+                         gl::Static);
+
+        uMvpMatrix = Matrix4f::ortho(0, 1, 0, 1);
+        uBufTex = color;
     }
 
     void release()
@@ -175,7 +172,16 @@ DENG2_PIMPL(GLFramebuffer)
         }
     }
 
-    void swapBuffers(Canvas &canvas)
+    void drawSwap()
+    {
+        if(isMultisampled())
+        {
+            target.updateFromProxy();
+        }
+        bufSwap.draw();
+    }
+
+    void swapBuffers(Canvas &canvas, gl::SwapBufferMode swapMode)
     {
         GLTarget defaultTarget;
 
@@ -184,24 +190,44 @@ DENG2_PIMPL(GLFramebuffer)
                 .setViewport(Rectangleui::fromSize(size))
                 .apply();
 
-        if(GLInfo::extensions().EXT_framebuffer_blit)
+        switch(swapMode)
         {
-            if(isMultisampled())
+        case gl::SwapMonoBuffer:
+            if(GLInfo::extensions().EXT_framebuffer_blit)
             {
-                multisampleTarget.blit(defaultTarget); // resolve multisampling to system backbuffer
+                if(isMultisampled())
+                {
+                    multisampleTarget.blit(defaultTarget); // resolve multisampling to system backbuffer
+                }
+                else
+                {
+                    target.blit(defaultTarget);  // copy to system backbuffer
+                }
             }
             else
             {
-                target.blit(defaultTarget);  // copy to system backbuffer
+                // Fallback: draw the back buffer texture to the main framebuffer.
+                bufSwap.draw();
             }
+            canvas.QGLWidget::swapBuffers();
+            break;
+
+        case gl::SwapStereoLeftBuffer:
+            glDrawBuffer(GL_BACK_LEFT);
+            drawSwap();
+            glDrawBuffer(GL_BACK);
+            break;
+
+        case gl::SwapStereoRightBuffer:
+            glDrawBuffer(GL_BACK_RIGHT);
+            drawSwap();
+            glDrawBuffer(GL_BACK);
+            break;
+
+        case gl::SwapStereoBuffers:
+            canvas.QGLWidget::swapBuffers();
+            break;
         }
-        else
-        {
-            // Fallback: draw the back buffer texture to the main framebuffer.
-            bufSwap.draw();
-        }
-
-        canvas.QGLWidget::swapBuffers();
 
         GLState::pop().apply();
     }
@@ -281,9 +307,9 @@ GLTexture &GLFramebuffer::depthStencilTexture() const
     return d->depthStencil;
 }
 
-void GLFramebuffer::swapBuffers(Canvas &canvas)
+void GLFramebuffer::swapBuffers(Canvas &canvas, gl::SwapBufferMode swapMode)
 {
-    d->swapBuffers(canvas);
+    d->swapBuffers(canvas, swapMode);
 }
 
 bool GLFramebuffer::setDefaultMultisampling(int sampleCount)