[core] Reduce number of varyings to 8 or less

For #pragmas, don't generate varyings for attributes that aren't used by the fragment shader. Pack other varyings more tightly.

6 files changed, 73 insertions, 83 deletions

diff --git a/scripts/generate-shaders.js b/scripts/generate-shaders.js
index 2f1f4c2f9c..2813d27365 100755
--- a/scripts/generate-shaders.js
+++ b/scripts/generate-shaders.js
@@ -61,42 +61,31 @@ ${fragmentPrelude}
     'symbol_icon',
     'symbol_sdf'
 ].forEach(function (shaderName) {
-    function applyPragmas(source, pragmas) {
-        return source.replace(/#pragma mapbox: ([\w]+) ([\w]+) ([\w]+) ([\w]+)/g, (match, operation, precision, type, name) => {
-            const a_type = type === "float" ? "vec2" : "vec4";
-            return pragmas[operation]
-                .join("\n")
-                .replace(/\{type\}/g, type)
-                .replace(/\{a_type}/g, a_type)
-                .replace(/\{precision\}/g, precision)
-                .replace(/\{name\}/g, name);
-        });
-    }
-
-    function vertexSource() {
-        const source = fs.readFileSync(path.join(inputPath, shaderName + '.vertex.glsl'), 'utf8');
-        return applyPragmas(source, {
-                define: [
-                    "uniform lowp float a_{name}_t;",
-                    "attribute {precision} {a_type} a_{name};",
-                    "varying {precision} {type} {name};"
-                ],
-                initialize: [
-                    "{name} = unpack_mix_{a_type}(a_{name}, a_{name}_t);"
-                ]
-            });
-    }
-
-    function fragmentSource() {
-        const source = fs.readFileSync(path.join(inputPath, shaderName + '.fragment.glsl'), 'utf8');
-        return applyPragmas(source, {
-                define: [
-                    "varying {precision} {type} {name};"
-                ],
-                initialize: [
-                ]
-            });
-    }
+    const re = /#pragma mapbox: ([\w]+) ([\w]+) ([\w]+) ([\w]+)/g;
+    const fragmentPragmas = new Set();
+
+    let fragmentSource = fs.readFileSync(path.join(inputPath, shaderName + '.fragment.glsl'), 'utf8');
+    let vertexSource = fs.readFileSync(path.join(inputPath, shaderName + '.vertex.glsl'), 'utf8');
+
+    fragmentSource = fragmentSource.replace(re, (match, operation, precision, type, name) => {
+        fragmentPragmas.add(name);
+        return operation === "define" ?
+            `varying ${precision} ${type} ${name};` :
+            ``;
+    });
+
+    vertexSource = vertexSource.replace(re, (match, operation, precision, type, name) => {
+        const a_type = type === "float" ? "vec2" : "vec4";
+        if (fragmentPragmas.has(name)) {
+            return operation === "define" ?
+                `uniform lowp float a_${name}_t;\nattribute ${precision} ${a_type} a_${name};\nvarying ${precision} ${type} ${name};` :
+                `${name} = unpack_mix_${a_type}(a_${name}, a_${name}_t);`;
+        } else {
+            return operation === "define" ?
+                `uniform lowp float a_${name}_t;\nattribute ${precision} ${a_type} a_${name};` :
+                `${precision} ${type} ${name} = unpack_mix_${a_type}(a_${name}, a_${name}_t);`;
+        }
+    });
 
     writeIfModified(path.join(outputPath, `${shaderName}.hpp`), `// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.
 
@@ -125,10 +114,10 @@ namespace shaders {
 
 const char* ${shaderName}::name = "${shaderName}";
 const char* ${shaderName}::vertexSource = R"MBGL_SHADER(
-${vertexSource()}
+${vertexSource}
 )MBGL_SHADER";
 const char* ${shaderName}::fragmentSource = R"MBGL_SHADER(
-${fragmentSource()}
+${fragmentSource}
 )MBGL_SHADER";
 
 } // namespace shaders
diff --git a/src/mbgl/shaders/circle.cpp b/src/mbgl/shaders/circle.cpp
index 1c977d2bce..2ecceeca70 100644
--- a/src/mbgl/shaders/circle.cpp
+++ b/src/mbgl/shaders/circle.cpp
@@ -35,8 +35,7 @@ uniform lowp float a_stroke_opacity_t;
 attribute lowp vec2 a_stroke_opacity;
 varying lowp float stroke_opacity;
 
-varying vec2 v_extrude;
-varying lowp float v_antialiasblur;
+varying vec3 v_data;
 
 void main(void) {
     color = unpack_mix_vec4(a_color, a_color_t);
@@ -48,23 +47,24 @@ void main(void) {
     stroke_opacity = unpack_mix_vec2(a_stroke_opacity, a_stroke_opacity_t);
 
     // unencode the extrusion vector that we snuck into the a_pos vector
-    v_extrude = vec2(mod(a_pos, 2.0) * 2.0 - 1.0);
+    vec2 extrude = vec2(mod(a_pos, 2.0) * 2.0 - 1.0);
 
-    vec2 extrude = v_extrude * (radius + stroke_width) * u_extrude_scale;
     // multiply a_pos by 0.5, since we had it * 2 in order to sneak
     // in extrusion data
     gl_Position = u_matrix * vec4(floor(a_pos * 0.5), 0, 1);
 
     if (u_scale_with_map) {
-        gl_Position.xy += extrude;
+        gl_Position.xy += extrude * (radius + stroke_width) * u_extrude_scale;
     } else {
-        gl_Position.xy += extrude * gl_Position.w;
+        gl_Position.xy += extrude * (radius + stroke_width) * u_extrude_scale * gl_Position.w;
     }
 
     // This is a minimum blur distance that serves as a faux-antialiasing for
     // the circle. since blur is a ratio of the circle's size and the intent is
     // to keep the blur at roughly 1px, the two are inversely related.
-    v_antialiasblur = 1.0 / DEVICE_PIXEL_RATIO / (radius + stroke_width);
+    lowp float antialiasblur = 1.0 / DEVICE_PIXEL_RATIO / (radius + stroke_width);
+
+    v_data = vec3(extrude.x, extrude.y, antialiasblur);
 }
 
 )MBGL_SHADER";
@@ -77,8 +77,7 @@ varying highp vec4 stroke_color;
 varying mediump float stroke_width;
 varying lowp float stroke_opacity;
 
-varying vec2 v_extrude;
-varying lowp float v_antialiasblur;
+varying vec3 v_data;
 
 void main() {
     
@@ -89,8 +88,11 @@ void main() {
     
     
 
-    float extrude_length = length(v_extrude);
-    float antialiased_blur = -max(blur, v_antialiasblur);
+    vec2 extrude = v_data.xy;
+    float extrude_length = length(extrude);
+
+    lowp float antialiasblur = v_data.z;
+    float antialiased_blur = -max(blur, antialiasblur);
 
     float opacity_t = smoothstep(0.0, antialiased_blur, extrude_length - 1.0);
 
diff --git a/src/mbgl/shaders/line.cpp b/src/mbgl/shaders/line.cpp
index 4392bd051f..e101cf6ee1 100644
--- a/src/mbgl/shaders/line.cpp
+++ b/src/mbgl/shaders/line.cpp
@@ -44,17 +44,15 @@ attribute lowp vec2 a_opacity;
 varying lowp float opacity;
 uniform lowp float a_gapwidth_t;
 attribute mediump vec2 a_gapwidth;
-varying mediump float gapwidth;
 uniform lowp float a_offset_t;
 attribute lowp vec2 a_offset;
-varying lowp float offset;
 
 void main() {
     color = unpack_mix_vec4(a_color, a_color_t);
     blur = unpack_mix_vec2(a_blur, a_blur_t);
     opacity = unpack_mix_vec2(a_opacity, a_opacity_t);
-    gapwidth = unpack_mix_vec2(a_gapwidth, a_gapwidth_t);
-    offset = unpack_mix_vec2(a_offset, a_offset_t);
+    mediump float gapwidth = unpack_mix_vec2(a_gapwidth, a_gapwidth_t);
+    lowp float offset = unpack_mix_vec2(a_offset, a_offset_t);
 
     vec2 a_extrude = a_data.xy - 128.0;
     float a_direction = mod(a_data.z, 4.0) - 1.0;
diff --git a/src/mbgl/shaders/line_pattern.cpp b/src/mbgl/shaders/line_pattern.cpp
index 6eb9d67700..a413d98e9f 100644
--- a/src/mbgl/shaders/line_pattern.cpp
+++ b/src/mbgl/shaders/line_pattern.cpp
@@ -44,16 +44,14 @@ attribute lowp vec2 a_opacity;
 varying lowp float opacity;
 uniform lowp float a_offset_t;
 attribute lowp vec2 a_offset;
-varying lowp float offset;
 uniform lowp float a_gapwidth_t;
 attribute mediump vec2 a_gapwidth;
-varying mediump float gapwidth;
 
 void main() {
     blur = unpack_mix_vec2(a_blur, a_blur_t);
     opacity = unpack_mix_vec2(a_opacity, a_opacity_t);
-    offset = unpack_mix_vec2(a_offset, a_offset_t);
-    gapwidth = unpack_mix_vec2(a_gapwidth, a_gapwidth_t);
+    lowp float offset = unpack_mix_vec2(a_offset, a_offset_t);
+    mediump float gapwidth = unpack_mix_vec2(a_gapwidth, a_gapwidth_t);
 
     vec2 a_extrude = a_data.xy - 128.0;
     float a_direction = mod(a_data.z, 4.0) - 1.0;
diff --git a/src/mbgl/shaders/line_sdf.cpp b/src/mbgl/shaders/line_sdf.cpp
index 17a6a19739..4f6cf814f9 100644
--- a/src/mbgl/shaders/line_sdf.cpp
+++ b/src/mbgl/shaders/line_sdf.cpp
@@ -52,17 +52,15 @@ attribute lowp vec2 a_opacity;
 varying lowp float opacity;
 uniform lowp float a_gapwidth_t;
 attribute mediump vec2 a_gapwidth;
-varying mediump float gapwidth;
 uniform lowp float a_offset_t;
 attribute lowp vec2 a_offset;
-varying lowp float offset;
 
 void main() {
     color = unpack_mix_vec4(a_color, a_color_t);
     blur = unpack_mix_vec2(a_blur, a_blur_t);
     opacity = unpack_mix_vec2(a_opacity, a_opacity_t);
-    gapwidth = unpack_mix_vec2(a_gapwidth, a_gapwidth_t);
-    offset = unpack_mix_vec2(a_offset, a_offset_t);
+    mediump float gapwidth = unpack_mix_vec2(a_gapwidth, a_gapwidth_t);
+    lowp float offset = unpack_mix_vec2(a_offset, a_offset_t);
 
     vec2 a_extrude = a_data.xy - 128.0;
     float a_direction = mod(a_data.z, 4.0) - 1.0;
diff --git a/src/mbgl/shaders/symbol_sdf.cpp b/src/mbgl/shaders/symbol_sdf.cpp
index 194e624036..0c39c5f4ac 100644
--- a/src/mbgl/shaders/symbol_sdf.cpp
+++ b/src/mbgl/shaders/symbol_sdf.cpp
@@ -57,10 +57,8 @@ uniform vec2 u_extrude_scale;
 
 uniform vec2 u_texsize;
 
-varying vec2 v_tex;
-varying vec2 v_fade_tex;
-varying float v_gamma_scale;
-varying float v_size;
+varying vec4 v_data0;
+varying vec2 v_data1;
 
 void main() {
     fill_color = unpack_mix_vec4(a_fill_color, a_fill_color_t);
@@ -81,6 +79,7 @@ void main() {
     mediump vec2 a_zoom = unpack_float(a_data[3]);
     mediump float a_minzoom = a_zoom[0];
     mediump float a_maxzoom = a_zoom[1];
+    float size;
 
     // In order to accommodate placing labels around corners in
     // symbol-placement: line, each glyph in a label could have multiple
@@ -92,22 +91,22 @@ void main() {
     // based on the scale of rendered text size relative to layout text size.
     mediump float layoutSize;
     if (!u_is_size_zoom_constant && !u_is_size_feature_constant) {
-        v_size = mix(a_size[0], a_size[1], u_size_t) / 10.0;
+        size = mix(a_size[0], a_size[1], u_size_t) / 10.0;
         layoutSize = a_size[2] / 10.0;
     } else if (u_is_size_zoom_constant && !u_is_size_feature_constant) {
-        v_size = a_size[0] / 10.0;
-        layoutSize = v_size;
+        size = a_size[0] / 10.0;
+        layoutSize = size;
     } else if (!u_is_size_zoom_constant && u_is_size_feature_constant) {
-        v_size = u_size;
+        size = u_size;
         layoutSize = u_layout_size;
     } else {
-        v_size = u_size;
+        size = u_size;
         layoutSize = u_size;
     }
 
-    float fontScale = u_is_text ? v_size / 24.0 : v_size;
+    float fontScale = u_is_text ? size / 24.0 : size;
 
-    mediump float zoomAdjust = log2(v_size / layoutSize);
+    mediump float zoomAdjust = log2(size / layoutSize);
     mediump float adjustedZoom = (u_zoom - zoomAdjust) * 10.0;
     // result: z = 0 if a_minzoom <= adjustedZoom < a_maxzoom, and 1 otherwise
     // Used below to move the vertex out of the clip space for when the current
@@ -156,10 +155,13 @@ void main() {
         gl_Position = u_matrix * vec4(a_pos, 0, 1) + vec4(extrude, 0, 0);
     }
 
-    v_gamma_scale = gl_Position.w;
+    float gamma_scale = gl_Position.w;
 
-    v_tex = a_tex / u_texsize;
-    v_fade_tex = vec2(a_labelminzoom / 255.0, 0.0);
+    vec2 tex = a_tex / u_texsize;
+    vec2 fade_tex = vec2(a_labelminzoom / 255.0, 0.0);
+
+    v_data0 = vec4(tex.x, tex.y, fade_tex.x, fade_tex.y);
+    v_data1 = vec2(gamma_scale, size);
 }
 
 )MBGL_SHADER";
@@ -179,10 +181,8 @@ uniform sampler2D u_fadetexture;
 uniform highp float u_gamma_scale;
 uniform bool u_is_text;
 
-varying vec2 v_tex;
-varying vec2 v_fade_tex;
-varying float v_gamma_scale;
-varying float v_size;
+varying vec4 v_data0;
+varying vec2 v_data1;
 
 void main() {
     
@@ -191,7 +191,12 @@ void main() {
     
     
 
-    float fontScale = u_is_text ? v_size / 24.0 : v_size;
+    vec2 tex = v_data0.xy;
+    vec2 fade_tex = v_data0.zw;
+    float gamma_scale = v_data1.x;
+    float size = v_data1.y;
+
+    float fontScale = u_is_text ? size / 24.0 : size;
 
     lowp vec4 color = fill_color;
     highp float gamma = EDGE_GAMMA / (fontScale * u_gamma_scale);
@@ -202,9 +207,9 @@ void main() {
         buff = (6.0 - halo_width / fontScale) / SDF_PX;
     }
 
-    lowp float dist = texture2D(u_texture, v_tex).a;
-    lowp float fade_alpha = texture2D(u_fadetexture, v_fade_tex).a;
-    highp float gamma_scaled = gamma * v_gamma_scale;
+    lowp float dist = texture2D(u_texture, tex).a;
+    lowp float fade_alpha = texture2D(u_fadetexture, fade_tex).a;
+    highp float gamma_scaled = gamma * gamma_scale;
     highp float alpha = smoothstep(buff - gamma_scaled, buff + gamma_scaled, dist) * fade_alpha;
 
     gl_FragColor = color * (alpha * opacity);