Implementation of multiple scenes example (#264)

examples/misc/CMakeLists.txt

@@ -5,3 +5,4 @@ add_example(NAME "mouse_key_listener")
 add_example(NAME "clipping" LINK_IMGUI)
 add_example(NAME "morphtargets" LINK_IMGUI)
 add_example(NAME "morphtargets_sphere" LINK_ASSIMP)
+add_example(NAME "multiple_scenes")

examples/misc/multiple_scenes.cpp

@@ -0,0 +1,102 @@
+#include "threepp/threepp.hpp"
+
+#include <cmath>
+
+using namespace threepp;
+
+struct MyMouseListener: MouseListener {
+
+    MyMouseListener(bool& d, int& slider, Canvas& c, OrbitControls& oc)
+        : dragging(d), sliderPos(slider), canvas(c), controls(oc) {}
+
+    void onMouseDown(int button, const Vector2& pos) override {
+        if (button == 0) {
+
+            // Check to see if we're within a short tolerance to the
+            // slider. Let's say 10 pixels for now.
+            constexpr float kSliderTol = 10.f;
+            if (std::abs(pos.x - static_cast<float>(sliderPos)) < kSliderTol) {
+                dragging = true;
+                controls.enabled = false;
+            }
+        }
+    }
+
+    void onMouseUp(int button, const Vector2& pos) override {
+        if (button == 0) {
+            dragging = false;
+            controls.enabled = true;
+        }
+    }
+
+    void onMouseMove(const Vector2& pos) override {
+        if (dragging) {
+            sliderPos = std::clamp(static_cast<int>(pos.x), 0, canvas.size().width);
+        }
+    }
+
+private:
+    bool& dragging;
+    int& sliderPos;
+    Canvas& canvas;
+    OrbitControls& controls;
+};
+
+int main() {
+
+    Canvas canvas("Multiple Scenes", {{"aa", 4}});
+
+    Scene sceneLeft;
+    sceneLeft.background = Color(0xBCD48F);
+
+    Scene sceneRight;
+    sceneRight.background = Color(0x8FBCD4);
+
+    auto geometry = IcosahedronGeometry::create(1, 3);
+
+    auto materialLeft = MeshStandardMaterial::create({{"color", Color::lightgrey}});
+    auto materialRight = MeshStandardMaterial::create({{"color", Color::gray}});
+    materialRight->wireframe = true;
+
+    auto meshLeft = Mesh::create(geometry, materialLeft);
+    sceneLeft.add(meshLeft);
+
+    auto meshRight = Mesh::create(geometry, materialRight);
+    sceneRight.add(meshRight);
+
+    auto camera = PerspectiveCamera::create(35, canvas.aspect(), 0.1f, 100);
+    camera->position.z = 6;
+
+    auto light = HemisphereLight::create(0xffffff, 0x444444);
+    light->position.set(-2, 2, 2);
+
+    sceneLeft.add(light);
+    sceneRight.add(light->clone());// need to clone second light for some reason
+
+    OrbitControls controls(*camera, canvas);
+
+    GLRenderer renderer(canvas.size());
+    renderer.setScissorTest(true);
+    renderer.setClearAlpha(0);
+    renderer.setClearColor(0);
+
+    canvas.onWindowResize([&](WindowSize size) {
+        camera->aspect = size.aspect();
+        camera->updateProjectionMatrix();
+        renderer.setSize(size);
+    });
+
+    int sliderPos = canvas.size().width / 2;
+    bool dragging = false;
+
+    MyMouseListener listener{dragging, sliderPos, canvas, controls};
+    canvas.addMouseListener(listener);
+
+    canvas.animate([&]() {
+        renderer.setScissor(0, 0, sliderPos, canvas.size().height);
+        renderer.render(sceneLeft, *camera);
+
+        renderer.setScissor(sliderPos, 0, canvas.size().width - sliderPos, canvas.size().height);
+        renderer.render(sceneRight, *camera);
+    });
+}