Merge branch 'master' into ls-android-readme-tweaksupstream/ls-android-readme-tweaks

1 files changed, 12 insertions, 1 deletions

diff --git a/src/mbgl/shaders/raster.cpp b/src/mbgl/shaders/raster.cpp
index eb7a2db240..98291bfec6 100644
--- a/src/mbgl/shaders/raster.cpp
+++ b/src/mbgl/shaders/raster.cpp
@@ -20,7 +20,12 @@ varying vec2 v_pos1;
 
 void main() {
     gl_Position = u_matrix * vec4(a_pos, 0, 1);
-    v_pos0 = (((a_texture_pos / 32767.0) - 0.5) / u_buffer_scale ) + 0.5;
+    // We are using Int16 for texture position coordinates to give us enough precision for
+    // fractional coordinates. We use 8192 to scale the texture coordinates in the buffer
+    // as an arbitrarily high number to preserve adequate precision when rendering.
+    // This is also the same value as the EXTENT we are using for our tile buffer pos coordinates,
+    // so math for modifying either is consistent.
+    v_pos0 = (((a_texture_pos / 8192.0) - 0.5) / u_buffer_scale ) + 0.5;
     v_pos1 = (v_pos0 * u_scale_parent) + u_tl_parent;
 }
 
@@ -45,6 +50,12 @@ void main() {
     // read and cross-fade colors from the main and parent tiles
     vec4 color0 = texture2D(u_image0, v_pos0);
     vec4 color1 = texture2D(u_image1, v_pos1);
+    if (color0.a > 0.0) {
+        color0.rgb = color0.rgb / color0.a;
+    }
+    if (color1.a > 0.0) {
+        color1.rgb = color1.rgb / color1.a;
+    }
     vec4 color = mix(color0, color1, u_fade_t);
     color.a *= u_opacity;
     vec3 rgb = color.rgb;