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.

7 files changed, 142 insertions, 114 deletions

diff --git a/src/mbgl/renderer/layers/render_fill_extrusion_layer.cpp b/src/mbgl/renderer/layers/render_fill_extrusion_layer.cpp
index 6295f62b21..fbd6160e8a 100644
--- a/src/mbgl/renderer/layers/render_fill_extrusion_layer.cpp
+++ b/src/mbgl/renderer/layers/render_fill_extrusion_layer.cpp
@@ -37,8 +37,9 @@ void RenderFillExtrusionLayer::transition(const TransitionParameters& parameters
 void RenderFillExtrusionLayer::evaluate(const PropertyEvaluationParameters& parameters) {
     evaluated = unevaluated.evaluate(parameters);
 
-    passes = (evaluated.get<style::FillExtrusionOpacity>() > 0) ? RenderPass::Translucent
-                                                         : RenderPass::None;
+    passes = (evaluated.get<style::FillExtrusionOpacity>() > 0)
+                 ? (RenderPass::Translucent | RenderPass::Pass3D)
+                 : RenderPass::None;
 }
 
 bool RenderFillExtrusionLayer::hasTransition() const {
@@ -50,113 +51,100 @@ void RenderFillExtrusionLayer::render(PaintParameters& parameters, RenderSource*
         return;
     }
 
-    const auto size = parameters.context.viewport.getCurrentValue().size;
+    if (parameters.pass == RenderPass::Pass3D) {
+        const auto& size = parameters.staticData.backendSize;
 
-    if (!parameters.staticData.extrusionTexture || parameters.staticData.extrusionTexture->getSize() != size) {
-        parameters.staticData.extrusionTexture = OffscreenTexture(parameters.context, size, OffscreenTextureAttachment::Depth);
-    }
-
-    parameters.staticData.extrusionTexture->bind();
-
-    parameters.context.setStencilMode(gl::StencilMode::disabled());
-    parameters.context.setDepthMode(parameters.depthModeForSublayer(0, gl::DepthMode::ReadWrite));
-    parameters.context.clear(Color{ 0.0f, 0.0f, 0.0f, 0.0f }, 1.0f, {});
-
-    if (evaluated.get<FillExtrusionPattern>().from.empty()) {
-        for (const RenderTile& tile : renderTiles) {
-            assert(dynamic_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl)));
-            FillExtrusionBucket& bucket = *reinterpret_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl));
-
-            parameters.programs.fillExtrusion.get(evaluated).draw(
-                parameters.context,
-                gl::Triangles(),
-                parameters.depthModeForSublayer(0, gl::DepthMode::ReadWrite),
-                gl::StencilMode::disabled(),
-                parameters.colorModeForRenderPass(),
-                FillExtrusionUniforms::values(
-                    tile.translatedClipMatrix(evaluated.get<FillExtrusionTranslate>(),
-                                              evaluated.get<FillExtrusionTranslateAnchor>(),
-                                              parameters.state),
-                    parameters.state,
-                    parameters.evaluatedLight
-                ),
-                *bucket.vertexBuffer,
-                *bucket.indexBuffer,
-                bucket.triangleSegments,
-                bucket.paintPropertyBinders.at(getID()),
-                evaluated,
-                parameters.state.getZoom(),
-                getID());
+        if (!renderTexture || renderTexture->getSize() != size) {
+            renderTexture = OffscreenTexture(parameters.context, size, *parameters.staticData.depthRenderbuffer);
         }
-    } else {
-        optional<ImagePosition> imagePosA = parameters.imageManager.getPattern(evaluated.get<FillExtrusionPattern>().from);
-        optional<ImagePosition> imagePosB = parameters.imageManager.getPattern(evaluated.get<FillExtrusionPattern>().to);
 
-        if (!imagePosA || !imagePosB) {
-            return;
+        renderTexture->bind();
+
+        optional<float> depthClearValue = {};
+        if (parameters.staticData.depthRenderbuffer->needsClearing()) depthClearValue = 1.0;
+        // Flag the depth buffer as no longer needing to be cleared for the remainder of this pass.
+        parameters.staticData.depthRenderbuffer->shouldClear(false);
+
+        parameters.context.setStencilMode(gl::StencilMode::disabled());
+        parameters.context.clear(Color{ 0.0f, 0.0f, 0.0f, 0.0f }, depthClearValue, {});
+
+        if (evaluated.get<FillExtrusionPattern>().from.empty()) {
+            for (const RenderTile& tile : renderTiles) {
+                assert(dynamic_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl)));
+                FillExtrusionBucket& bucket =
+                    *reinterpret_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl));
+
+                parameters.programs.fillExtrusion.get(evaluated).draw(
+                    parameters.context, gl::Triangles(),
+                    parameters.depthModeFor3D(gl::DepthMode::ReadWrite),
+                    gl::StencilMode::disabled(), parameters.colorModeForRenderPass(),
+                    FillExtrusionUniforms::values(
+                        tile.translatedClipMatrix(evaluated.get<FillExtrusionTranslate>(),
+                                                  evaluated.get<FillExtrusionTranslateAnchor>(),
+                                                  parameters.state),
+                        parameters.state, parameters.evaluatedLight),
+                    *bucket.vertexBuffer, *bucket.indexBuffer, bucket.triangleSegments,
+                    bucket.paintPropertyBinders.at(getID()), evaluated, parameters.state.getZoom(),
+                    getID());
+            }
+        } else {
+            optional<ImagePosition> imagePosA =
+                parameters.imageManager.getPattern(evaluated.get<FillExtrusionPattern>().from);
+            optional<ImagePosition> imagePosB =
+                parameters.imageManager.getPattern(evaluated.get<FillExtrusionPattern>().to);
+
+            if (!imagePosA || !imagePosB) {
+                return;
+            }
+
+            parameters.imageManager.bind(parameters.context, 0);
+
+            for (const RenderTile& tile : renderTiles) {
+                assert(dynamic_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl)));
+                FillExtrusionBucket& bucket =
+                    *reinterpret_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl));
+
+                parameters.programs.fillExtrusionPattern.get(evaluated).draw(
+                    parameters.context, gl::Triangles(),
+                    parameters.depthModeFor3D(gl::DepthMode::ReadWrite),
+                    gl::StencilMode::disabled(), parameters.colorModeForRenderPass(),
+                    FillExtrusionPatternUniforms::values(
+                        tile.translatedClipMatrix(evaluated.get<FillExtrusionTranslate>(),
+                                                  evaluated.get<FillExtrusionTranslateAnchor>(),
+                                                  parameters.state),
+                        parameters.imageManager.getPixelSize(), *imagePosA, *imagePosB,
+                        evaluated.get<FillExtrusionPattern>(), tile.id, parameters.state,
+                        -std::pow(2, tile.id.canonical.z) / util::tileSize / 8.0f,
+                        parameters.evaluatedLight),
+                    *bucket.vertexBuffer, *bucket.indexBuffer, bucket.triangleSegments,
+                    bucket.paintPropertyBinders.at(getID()), evaluated, parameters.state.getZoom(),
+                    getID());
+            }
         }
 
-        parameters.imageManager.bind(parameters.context, 0);
-
-        for (const RenderTile& tile : renderTiles) {
-            assert(dynamic_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl)));
-            FillExtrusionBucket& bucket = *reinterpret_cast<FillExtrusionBucket*>(tile.tile.getBucket(*baseImpl));
-
-            parameters.programs.fillExtrusionPattern.get(evaluated).draw(
-                parameters.context,
-                gl::Triangles(),
-                parameters.depthModeForSublayer(0, gl::DepthMode::ReadWrite),
-                gl::StencilMode::disabled(),
-                parameters.colorModeForRenderPass(),
-                FillExtrusionPatternUniforms::values(
-                    tile.translatedClipMatrix(evaluated.get<FillExtrusionTranslate>(),
-                                              evaluated.get<FillExtrusionTranslateAnchor>(),
-                                              parameters.state),
-                    parameters.imageManager.getPixelSize(),
-                    *imagePosA,
-                    *imagePosB,
-                    evaluated.get<FillExtrusionPattern>(),
-                    tile.id,
-                    parameters.state,
-                    -std::pow(2, tile.id.canonical.z) / util::tileSize / 8.0f,
-                    parameters.evaluatedLight
-                ),
-                *bucket.vertexBuffer,
-                *bucket.indexBuffer,
-                bucket.triangleSegments,
-                bucket.paintPropertyBinders.at(getID()),
-                evaluated,
-                parameters.state.getZoom(),
-                getID());
-        }
-    }
+    } else if (parameters.pass == RenderPass::Translucent) {
+        parameters.context.bindTexture(renderTexture->getTexture());
 
-    parameters.backend.bind();
-    parameters.context.bindTexture(parameters.staticData.extrusionTexture->getTexture());
-
-    mat4 viewportMat;
-    matrix::ortho(viewportMat, 0, size.width, size.height, 0, 0, 1);
-
-    const Properties<>::PossiblyEvaluated properties;
-
-    parameters.programs.extrusionTexture.draw(
-        parameters.context,
-        gl::Triangles(),
-        gl::DepthMode::disabled(),
-        gl::StencilMode::disabled(),
-        parameters.colorModeForRenderPass(),
-        ExtrusionTextureProgram::UniformValues{
-            uniforms::u_matrix::Value{ viewportMat }, uniforms::u_world::Value{ size },
-            uniforms::u_image::Value{ 0 },
-            uniforms::u_opacity::Value{ evaluated.get<FillExtrusionOpacity>() }
-        },
-        parameters.staticData.extrusionTextureVertexBuffer,
-        parameters.staticData.quadTriangleIndexBuffer,
-        parameters.staticData.extrusionTextureSegments,
-        ExtrusionTextureProgram::PaintPropertyBinders{ properties, 0 },
-        properties,
-        parameters.state.getZoom(),
-        getID());
+        const auto& size = parameters.staticData.backendSize;
+
+        mat4 viewportMat;
+        matrix::ortho(viewportMat, 0, size.width, size.height, 0, 0, 1);
+
+        const Properties<>::PossiblyEvaluated properties;
+
+        parameters.programs.extrusionTexture.draw(
+            parameters.context, gl::Triangles(), gl::DepthMode::disabled(),
+            gl::StencilMode::disabled(), parameters.colorModeForRenderPass(),
+            ExtrusionTextureProgram::UniformValues{
+                uniforms::u_matrix::Value{ viewportMat }, uniforms::u_world::Value{ size },
+                uniforms::u_image::Value{ 0 },
+                uniforms::u_opacity::Value{ evaluated.get<FillExtrusionOpacity>() } },
+            parameters.staticData.extrusionTextureVertexBuffer,
+            parameters.staticData.quadTriangleIndexBuffer,
+            parameters.staticData.extrusionTextureSegments,
+            ExtrusionTextureProgram::PaintPropertyBinders{ properties, 0 }, properties,
+            parameters.state.getZoom(), getID());
+    }
 }
 
 bool RenderFillExtrusionLayer::queryIntersectsFeature(
diff --git a/src/mbgl/renderer/layers/render_fill_extrusion_layer.hpp b/src/mbgl/renderer/layers/render_fill_extrusion_layer.hpp
index a53e00ca6f..838494cf91 100644
--- a/src/mbgl/renderer/layers/render_fill_extrusion_layer.hpp
+++ b/src/mbgl/renderer/layers/render_fill_extrusion_layer.hpp
@@ -3,6 +3,8 @@
 #include <mbgl/renderer/render_layer.hpp>
 #include <mbgl/style/layers/fill_extrusion_layer_impl.hpp>
 #include <mbgl/style/layers/fill_extrusion_layer_properties.hpp>
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/offscreen_texture.hpp>
 
 namespace mbgl {
 
@@ -30,6 +32,8 @@ public:
     style::FillExtrusionPaintProperties::PossiblyEvaluated evaluated;
 
     const style::FillExtrusionLayer::Impl& impl() const;
+
+    optional<OffscreenTexture> renderTexture;
 };
 
 template <>
diff --git a/src/mbgl/renderer/paint_parameters.cpp b/src/mbgl/renderer/paint_parameters.cpp
index 584dcdf118..299db844bc 100644
--- a/src/mbgl/renderer/paint_parameters.cpp
+++ b/src/mbgl/renderer/paint_parameters.cpp
@@ -62,6 +62,10 @@ gl::DepthMode PaintParameters::depthModeForSublayer(uint8_t n, gl::DepthMode::Ma
     return gl::DepthMode { gl::DepthMode::LessEqual, mask, { nearDepth, farDepth } };
 }
 
+gl::DepthMode PaintParameters::depthModeFor3D(gl::DepthMode::Mask mask) const {
+    return gl::DepthMode { gl::DepthMode::LessEqual, mask, { 0.0, 1.0 } };
+}
+
 gl::StencilMode PaintParameters::stencilModeForClipping(const ClipID& id) const {
     return gl::StencilMode {
         gl::StencilMode::Equal { static_cast<uint32_t>(id.mask.to_ulong()) },
diff --git a/src/mbgl/renderer/paint_parameters.hpp b/src/mbgl/renderer/paint_parameters.hpp
index eb1ad73ad5..4a2c2c6f12 100644
--- a/src/mbgl/renderer/paint_parameters.hpp
+++ b/src/mbgl/renderer/paint_parameters.hpp
@@ -60,6 +60,7 @@ public:
     Programs& programs;
 
     gl::DepthMode depthModeForSublayer(uint8_t n, gl::DepthMode::Mask) const;
+    gl::DepthMode depthModeFor3D(gl::DepthMode::Mask) const;
     gl::StencilMode stencilModeForClipping(const ClipID&) const;
     gl::ColorMode colorModeForRenderPass() const;
 
diff --git a/src/mbgl/renderer/render_pass.hpp b/src/mbgl/renderer/render_pass.hpp
index ae2b923ba1..5d18304129 100644
--- a/src/mbgl/renderer/render_pass.hpp
+++ b/src/mbgl/renderer/render_pass.hpp
@@ -11,6 +11,7 @@ enum class RenderPass : uint8_t {
     None = 0,
     Opaque = 1 << 0,
     Translucent = 1 << 1,
+    Pass3D = 1 << 2,
 };
 
 MBGL_CONSTEXPR RenderPass operator|(RenderPass a, RenderPass b) {
diff --git a/src/mbgl/renderer/render_static_data.hpp b/src/mbgl/renderer/render_static_data.hpp
index 07a47b4c8f..cf58c31f4d 100644
--- a/src/mbgl/renderer/render_static_data.hpp
+++ b/src/mbgl/renderer/render_static_data.hpp
@@ -4,7 +4,6 @@
 #include <mbgl/gl/index_buffer.hpp>
 #include <mbgl/programs/programs.hpp>
 #include <mbgl/util/optional.hpp>
-#include <mbgl/util/offscreen_texture.hpp>
 
 #include <string>
 
@@ -26,7 +25,9 @@ public:
     SegmentVector<RasterAttributes> rasterSegments;
     SegmentVector<ExtrusionTextureAttributes> extrusionTextureSegments;
 
-    optional<OffscreenTexture> extrusionTexture;
+    optional<gl::Renderbuffer<gl::RenderbufferType::DepthComponent>> depthRenderbuffer;
+    bool has3D = false;
+    Size backendSize;
 
     Programs programs;
 
diff --git a/src/mbgl/renderer/renderer_impl.cpp b/src/mbgl/renderer/renderer_impl.cpp
index a5d23333ac..c45295b693 100644
--- a/src/mbgl/renderer/renderer_impl.cpp
+++ b/src/mbgl/renderer/renderer_impl.cpp
@@ -13,6 +13,7 @@
 #include <mbgl/renderer/render_tile.hpp>
 #include <mbgl/renderer/layers/render_background_layer.hpp>
 #include <mbgl/renderer/layers/render_custom_layer.hpp>
+#include <mbgl/renderer/layers/render_fill_extrusion_layer.hpp>
 #include <mbgl/renderer/style_diff.hpp>
 #include <mbgl/renderer/query.hpp>
 #include <mbgl/renderer/backend_scope.hpp>
@@ -276,6 +277,10 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
         RenderLayer* layer = getRenderLayer(layerImpl->id);
         assert(layer);
 
+        if (!parameters.staticData.has3D && layer->is<RenderFillExtrusionLayer>()) {
+            parameters.staticData.has3D = true;
+        }
+
         if (!layer->needsRendering(zoomHistory.lastZoom)) {
             continue;
         }
@@ -372,6 +377,39 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
         parameters.imageManager.upload(parameters.context, 0);
         parameters.lineAtlas.upload(parameters.context, 0);
         parameters.frameHistory.upload(parameters.context, 0);
+
+        // Update all clipping IDs + upload buckets.
+        for (const auto& entry : renderSources) {
+            if (entry.second->isEnabled()) {
+                entry.second->startRender(parameters);
+            }
+        }
+    }
+
+    // - 3D PASS -------------------------------------------------------------------------------------
+    // Renders any 3D layers bottom-to-top to unique FBOs with texture attachments, but share the same
+    // depth rbo between them.
+    if (parameters.staticData.has3D) {
+        parameters.staticData.backendSize = parameters.backend.getFramebufferSize();
+
+        MBGL_DEBUG_GROUP(parameters.context, "3d");
+        parameters.pass = RenderPass::Pass3D;
+
+        if (!parameters.staticData.depthRenderbuffer ||
+            parameters.staticData.depthRenderbuffer->size != parameters.staticData.backendSize) {
+            parameters.staticData.depthRenderbuffer =
+                parameters.context.createRenderbuffer<gl::RenderbufferType::DepthComponent>(parameters.staticData.backendSize);
+        }
+        parameters.staticData.depthRenderbuffer->shouldClear(true);
+
+        uint32_t i = static_cast<uint32_t>(order.size()) - 1;
+        for (auto it = order.begin(); it != order.end(); ++it, --i) {
+            parameters.currentLayer = i;
+            if (it->layer.hasRenderPass(parameters.pass)) {
+                MBGL_DEBUG_GROUP(parameters.context, it->layer.getID());
+                it->layer.render(parameters, it->source);
+            }
+        }
     }
 
     // - CLEAR -------------------------------------------------------------------------------------
@@ -390,15 +428,6 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
     // - CLIPPING MASKS ----------------------------------------------------------------------------
     // Draws the clipping masks to the stencil buffer.
     {
-        MBGL_DEBUG_GROUP(parameters.context, "clip");
-
-        // Update all clipping IDs.
-        for (const auto& entry : renderSources) {
-            if (entry.second->isEnabled()) {
-                entry.second->startRender(parameters);
-            }
-        }
-
         MBGL_DEBUG_GROUP(parameters.context, "clipping masks");
 
         static const style::FillPaintProperties::PossiblyEvaluated properties {};