Preserve depth buffer between 3D layers + optimize render order (#9931)

Port of https://github.com/mapbox/mapbox-gl-js/pull/5101: adds a new render pass `Pass3D` before any other rendering wherein we render layers with 3D passes (fill-extrusion layers) to offscreen framebuffers, sharing a depth renderbuffer between those layers in order to render 3D space correctly. Those framebuffers are saved on the RenderLayers and copied back to the map during the translucent pass. Rendering to offscreen framebuffers before we do any clear + draw means we can avoid expensive framebuffer restores.

2 files changed, 18 insertions, 1 deletions

diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index 49bfe30e91..b8a0502178 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -457,6 +457,9 @@ Framebuffer Context::createFramebuffer(const Texture& color) {
 Framebuffer
 Context::createFramebuffer(const Texture& color,
                            const Renderbuffer<RenderbufferType::DepthComponent>& depthTarget) {
+    if (color.size != depthTarget.size) {
+        throw std::runtime_error("Renderbuffer size mismatch");
+    }
     auto fbo = createFramebuffer();
     bindFramebuffer = fbo;
     MBGL_CHECK_ERROR(glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color.texture, 0));
diff --git a/src/mbgl/gl/renderbuffer.hpp b/src/mbgl/gl/renderbuffer.hpp
index cc8ff13268..0592557a7f 100644
--- a/src/mbgl/gl/renderbuffer.hpp
+++ b/src/mbgl/gl/renderbuffer.hpp
@@ -9,9 +9,23 @@ namespace gl {
 template <RenderbufferType renderbufferType>
 class Renderbuffer {
 public:
+    Renderbuffer(Size size_, UniqueRenderbuffer renderbuffer_, bool dirty_ = false)
+        : size(std::move(size_)), renderbuffer(std::move(renderbuffer_)), dirty(dirty_) {
+    }
+
     using type = std::integral_constant<RenderbufferType, renderbufferType>;
     Size size;
-    gl::UniqueRenderbuffer renderbuffer;
+    UniqueRenderbuffer renderbuffer;
+
+    void shouldClear(bool clear) {
+        dirty = clear;
+    }
+    bool needsClearing() {
+        return dirty;
+    }
+
+private:
+    bool dirty;
 };
 
 } // namespace gl