fix depth clipping in perspective view

The depth range is now set slightly differently. Both ends of the range
are shifted for each layer to solve some precision issues.

Some layers draw multiple things at different depths. For example, fill
layers draw fills and antialiasing separately. To handle this case, I
added setDepthSublayer(n) which a

10 files changed, 33 insertions, 34 deletions

diff --git a/src/mbgl/map/transform_state.cpp b/src/mbgl/map/transform_state.cpp
index c06d944d97..2f62318281 100644
--- a/src/mbgl/map/transform_state.cpp
+++ b/src/mbgl/map/transform_state.cpp
@@ -39,7 +39,7 @@ void TransformState::getProjMatrix(mat4& projMatrix) const {
     matrix::rotate_z(projMatrix, projMatrix, getAngle());
 
     matrix::translate(projMatrix, projMatrix, pixel_x() - getWidth() / 2.0f,
-            pixel_y() - getWidth() / 2.0f, 0);
+            pixel_y() - getHeight() / 2.0f, 0);
 }
 
 box TransformState::cornersToBox(uint32_t z) const {
diff --git a/src/mbgl/map/transform_state.hpp b/src/mbgl/map/transform_state.hpp
index 5b648ad07d..521131b33a 100644
--- a/src/mbgl/map/transform_state.hpp
+++ b/src/mbgl/map/transform_state.hpp
@@ -93,7 +93,7 @@ private:
     double angle = 0;
     double scale = 1;
     double altitude = 1.5;
-    double pitch = 0.001;
+    double pitch = 0.0;
 
     // cache values for spherical mercator math
     double Bc = (scale * util::tileSize) / 360;
diff --git a/src/mbgl/renderer/gl_config.hpp b/src/mbgl/renderer/gl_config.hpp
index b2a2dcb2a9..59507f721f 100644
--- a/src/mbgl/renderer/gl_config.hpp
+++ b/src/mbgl/renderer/gl_config.hpp
@@ -117,7 +117,6 @@ struct DepthTest {
     static const Type Default;
     inline static void Set(const Type& value) {
         MBGL_CHECK_ERROR(value ? glEnable(GL_DEPTH_TEST) : glDisable(GL_DEPTH_TEST));
-        //MBGL_CHECK_ERROR(glDisable(GL_DEPTH_TEST));
     }
 };
 
diff --git a/src/mbgl/renderer/painter.cpp b/src/mbgl/renderer/painter.cpp
index 74268a4017..6b78ca40d3 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -154,10 +154,6 @@ void Painter::clear() {
     MBGL_CHECK_ERROR(glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT | GL_DEPTH_BUFFER_BIT));
 }
 
-void Painter::setStrata(float value) {
-    strata = value;
-}
-
 void Painter::prepareTile(const Tile& tile) {
     const GLint ref = (GLint)tile.clip.reference.to_ulong();
     const GLuint mask = (GLuint)tile.clip.mask.to_ulong();
@@ -223,19 +219,19 @@ void Painter::render(const Style& style, TransformState state_, const FrameData&
     if (debug::renderTree) { Log::Info(Event::Render, "{"); indent++; }
 
     // TODO: Correctly compute the number of layers recursively beforehand.
-    const float strataThickness = 1.0f / (order.size() + 1);
+    depthRangeSize = 1 - (order.size() + 2) * numSublayers * depthEpsilon;
 
     // - OPAQUE PASS -------------------------------------------------------------------------------
     // Render everything top-to-bottom by using reverse iterators. Render opaque objects first.
     renderPass(RenderPass::Opaque,
                order.rbegin(), order.rend(),
-               0, 1, strataThickness);
+               0, 1);
 
     // - TRANSLUCENT PASS --------------------------------------------------------------------------
     // Make a second pass, rendering translucent objects. This time, we render bottom-to-top.
     renderPass(RenderPass::Translucent,
                order.begin(), order.end(),
-               order.size() - 1, -1, strataThickness);
+               order.size() - 1, -1);
 
     if (debug::renderTree) { Log::Info(Event::Render, "}"); indent--; }
 
@@ -266,8 +262,7 @@ void Painter::render(const Style& style, TransformState state_, const FrameData&
 template <class Iterator>
 void Painter::renderPass(RenderPass pass_,
                          Iterator it, Iterator end,
-                         std::size_t i, int8_t increment,
-                         const float strataThickness) {
+                         std::size_t i, int8_t increment) {
     pass = pass_;
 
     const double zoom = state.getZoom();
@@ -282,6 +277,7 @@ void Painter::renderPass(RenderPass pass_,
     config.blend = pass == RenderPass::Translucent;
 
     for (; it != end; ++it, i += increment) {
+        currentLayer = i;
         const auto& item = *it;
         if (item.bucket && item.tile) {
             // Skip this layer if it's outside the range of min/maxzoom.
@@ -293,13 +289,11 @@ void Painter::renderPass(RenderPass pass_,
             }
             if (item.layer.hasRenderPass(pass)) {
                 MBGL_DEBUG_GROUP(item.layer.id + " - " + std::string(item.tile->id));
-                setStrata(i * strataThickness);
                 prepareTile(*item.tile);
                 item.bucket->render(*this, item.layer, item.tile->id, item.tile->matrix);
             }
         } else {
             MBGL_DEBUG_GROUP("background");
-            setStrata(i * strataThickness);
             renderBackground(item.layer);
         }
     }
@@ -426,7 +420,8 @@ void Painter::renderBackground(const StyleLayer &layer_desc) {
 
     config.stencilTest = false;
     config.depthTest = true;
-    config.depthRange = { strata + strata_epsilon, 1.0f };
+    config.depthRange = { 1.0f, 1.0f };
+
     MBGL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, 4));
 }
 
@@ -455,3 +450,9 @@ mat4 Painter::translatedMatrix(const mat4& matrix, const std::array<float, 2> &t
         return vtxMatrix;
     }
 }
+
+void Painter::setDepthSublayer(int n) {
+    float nearDepth = ((1 + currentLayer) * numSublayers + n) * depthEpsilon;
+    float farDepth = nearDepth + depthRangeSize;
+    config.depthRange = { nearDepth, farDepth };
+}
diff --git a/src/mbgl/renderer/painter.hpp b/src/mbgl/renderer/painter.hpp
index 78cf308b7b..da67ffdd7d 100644
--- a/src/mbgl/renderer/painter.hpp
+++ b/src/mbgl/renderer/painter.hpp
@@ -123,9 +123,6 @@ public:
     // Changes whether debug information is drawn onto the map
     void setDebug(bool enabled);
 
-    // Configures the painter strata that is used for early z-culling of fragments.
-    void setStrata(float strata);
-
     void drawClippingMasks(const std::set<Source*>&);
     void drawClippingMask(const mat4& matrix, const ClipID& clip);
 
@@ -146,8 +143,7 @@ private:
     template <class Iterator>
     void renderPass(RenderPass,
                     Iterator it, Iterator end,
-                    std::size_t i, int8_t iIncrement,
-                    const float strataThickness);
+                    std::size_t i, int8_t increment);
 
     void prepareTile(const Tile& tile);
 
@@ -162,6 +158,8 @@ private:
                    SDFShader& sdfShader,
                    void (SymbolBucket::*drawSDF)(SDFShader&));
 
+    void setDepthSublayer(int n);
+
 public:
     void useProgram(uint32_t program);
     void lineWidth(float lineWidth);
@@ -199,13 +197,16 @@ private:
     uint32_t gl_program = 0;
     float gl_lineWidth = 0;
     std::array<uint16_t, 2> gl_viewport = {{ 0, 0 }};
-    float strata = 0;
     RenderPass pass = RenderPass::Opaque;
-    const float strata_epsilon = 1.0f / (1 << 16);
     Color background = {{ 0, 0, 0, 0 }};
 
     std::vector<RenderItem> order;
 
+    int numSublayers = 3;
+    int currentLayer;
+    float depthRangeSize;
+    const float depthEpsilon = 1.0f / (1 << 16);
+
 public:
     FrameHistory frameHistory;
 
diff --git a/src/mbgl/renderer/painter_fill.cpp b/src/mbgl/renderer/painter_fill.cpp
index 414ec2bbcb..d27feb4693 100644
--- a/src/mbgl/renderer/painter_fill.cpp
+++ b/src/mbgl/renderer/painter_fill.cpp
@@ -55,7 +55,7 @@ void Painter::renderFill(FillBucket& bucket, const StyleLayer &layer_desc, const
             static_cast<float>(frame.framebufferSize[0]),
             static_cast<float>(frame.framebufferSize[1])
         }};
-        config.depthRange = { strata, 1.0f };
+        setDepthSublayer(0);
         bucket.drawVertices(*outlineShader);
     }
 
@@ -95,7 +95,7 @@ void Painter::renderFill(FillBucket& bucket, const StyleLayer &layer_desc, const
 
             // Draw the actual triangles into the color & stencil buffer.
             config.depthMask = GL_TRUE;
-            config.depthRange = { strata, 1.0f };
+            setDepthSublayer(0);
             bucket.drawElements(*patternShader);
         }
     }
@@ -112,7 +112,7 @@ void Painter::renderFill(FillBucket& bucket, const StyleLayer &layer_desc, const
 
             // Draw the actual triangles into the color & stencil buffer.
             config.depthMask = GL_TRUE;
-            config.depthRange = { strata + strata_epsilon, 1.0f };
+            setDepthSublayer(1);
             bucket.drawElements(*plainShader);
         }
     }
@@ -132,7 +132,7 @@ void Painter::renderFill(FillBucket& bucket, const StyleLayer &layer_desc, const
             static_cast<float>(frame.framebufferSize[1])
         }};
 
-        config.depthRange = { strata + strata_epsilon + strata_epsilon, 1.0f };
+        setDepthSublayer(2);
         bucket.drawVertices(*outlineShader);
     }
 }
diff --git a/src/mbgl/renderer/painter_line.cpp b/src/mbgl/renderer/painter_line.cpp
index cf586c05e7..0b7e8a96f7 100644
--- a/src/mbgl/renderer/painter_line.cpp
+++ b/src/mbgl/renderer/painter_line.cpp
@@ -67,7 +67,7 @@ void Painter::renderLine(LineBucket& bucket, const StyleLayer &layer_desc, const
 
     mat4 vtxMatrix = translatedMatrix(matrix, properties.translate, id, properties.translateAnchor);
 
-    config.depthRange = { strata, 1.0f };
+    setDepthSublayer(0);
 
     if (!properties.dash_array.from.empty()) {
 
@@ -125,7 +125,6 @@ void Painter::renderLine(LineBucket& bucket, const StyleLayer &layer_desc, const
 
         MBGL_CHECK_ERROR(glActiveTexture(GL_TEXTURE0));
         spriteAtlas->bind(true);
-        config.depthRange = { strata + strata_epsilon, 1.0f };  // may or may not matter
 
         bucket.drawLinePatterns(*linepatternShader);
 
diff --git a/src/mbgl/renderer/painter_raster.cpp b/src/mbgl/renderer/painter_raster.cpp
index 2a8f8e7078..70cbcb4ca5 100644
--- a/src/mbgl/renderer/painter_raster.cpp
+++ b/src/mbgl/renderer/painter_raster.cpp
@@ -24,7 +24,7 @@ void Painter::renderRaster(RasterBucket& bucket, const StyleLayer &layer_desc, c
 
         config.stencilTest = true;
         config.depthTest = true;
-        config.depthRange = { strata + strata_epsilon, 1.0f };
+        setDepthSublayer(0);
         bucket.drawRaster(*rasterShader, tileStencilBuffer, coveringRasterArray);
     }
 }
diff --git a/src/mbgl/renderer/painter_symbol.cpp b/src/mbgl/renderer/painter_symbol.cpp
index c64f32620a..c6ea372398 100644
--- a/src/mbgl/renderer/painter_symbol.cpp
+++ b/src/mbgl/renderer/painter_symbol.cpp
@@ -100,7 +100,7 @@ void Painter::renderSDF(SymbolBucket &bucket,
 
         sdfShader.u_buffer = (haloOffset - styleProperties.halo_width / fontScale) / sdfPx;
 
-        config.depthRange = { strata, 1.0f };
+        setDepthSublayer(0);
         (bucket.*drawSDF)(sdfShader);
     }
 
@@ -121,7 +121,7 @@ void Painter::renderSDF(SymbolBucket &bucket,
 
         sdfShader.u_buffer = (256.0f - 64.0f) / 256.0f;
 
-        config.depthRange = { strata + strata_epsilon, 1.0f };
+        setDepthSublayer(1);
         (bucket.*drawSDF)(sdfShader);
     }
 }
@@ -147,7 +147,7 @@ void Painter::renderSymbol(SymbolBucket &bucket, const StyleLayer &layer_desc, c
         collisionBoxShader->u_maxzoom = (id.z + 1) * 10;
         lineWidth(1.0f);
 
-        config.depthRange = { strata, 1.0f };
+        setDepthSublayer(0);
         bucket.drawCollisionBoxes(*collisionBoxShader);
 
     }
@@ -230,7 +230,7 @@ void Painter::renderSymbol(SymbolBucket &bucket, const StyleLayer &layer_desc, c
             iconShader->u_fadezoom = state.getNormalizedZoom() * 10;
             iconShader->u_opacity = properties.icon.opacity;
 
-            config.depthRange = { strata, 1.0f };
+            setDepthSublayer(0);
             bucket.drawIcons(*iconShader);
         }
     }
diff --git a/src/mbgl/shader/plain.vertex.glsl b/src/mbgl/shader/plain.vertex.glsl
index 7ccbed12b9..866c3cd2f3 100644
--- a/src/mbgl/shader/plain.vertex.glsl
+++ b/src/mbgl/shader/plain.vertex.glsl
@@ -4,5 +4,4 @@ uniform mat4 u_matrix;
 
 void main() {
     gl_Position = u_matrix * vec4(a_pos, 0, 1);
-    gl_Position.z = 1.0;
 }