Add ViewerRenderer::query3DPosition

viewer/glow-extras/viewer/ViewerRenderer.cc

@@ -159,6 +159,42 @@ void glow::viewer::ViewerRenderer::maximizeSamples()
     mSSAOSamples = 256;
 }
 
+tg::optional<tg::pos3> glow::viewer::ViewerRenderer::query3DPosition(const tg::isize2& resolution,
+                                                                     tg::ipos2 pixel,
+                                                                     glow::viewer::SubViewData& subViewData,
+                                                                     glow::viewer::CameraController& cam) const
+{
+    if (pixel.x >= resolution.width || pixel.y >= resolution.height)
+        return {};
+
+    // rescale position
+    pixel.y = resolution.height - pixel.y - 1;
+
+    float d;
+
+    {
+        auto fb = mFramebuffer->bind();
+        fb.attachDepth(subViewData.targetDepth);
+        glReadPixels(static_cast<int>(pixel.x), static_cast<int>(pixel.y), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &d);
+    }
+
+    if (d < 1.f)
+    {
+        // unproject (with viewport coords!)
+        tg::vec4 v{pixel.x / float(resolution.width) * 2 - 1, pixel.y / float(resolution.height) * 2 - 1, d * 2 - 1, 1.0};
+
+        v = tg::inverse(cam.computeProjMatrix()) * v;
+        v /= v.w;
+        v = tg::inverse(cam.computeViewMatrix()) * v;
+
+        return tg::pos3(v);
+    }
+    else
+    {
+        return {};
+    }
+}
+
 void glow::viewer::ViewerRenderer::renderSubview(tg::isize2 const& res, tg::ipos2 const& offset, SubViewData& subViewData, Scene const& scene, glow::viewer::CameraController& cam)
 {
     if (scene.clearAccumulation)

viewer/glow-extras/viewer/ViewerRenderer.hh

@@ -80,6 +80,8 @@ public:
     void endFrame(float approximateRenderTime = 0.f);
     void maximizeSamples();
     void set_2d_transform(tg::mat3x2 const& transform) { mVectorRenderer.set_global_transform(transform); }
+
+    tg::optional<tg::pos3> query3DPosition(tg::isize2 const& resolution, tg::ipos2 pixel, SubViewData& subViewData, CameraController& cam) const;
 };