feat: add box shadows (#16)

1 files changed, 17 insertions, 0 deletions

diff --git a/render/fx_renderer/gles2/shaders/stencil_mask.frag b/render/fx_renderer/gles2/shaders/stencil_mask.frag
new file mode 100644
index 0000000..ee03307
--- /dev/null
+++ b/render/fx_renderer/gles2/shaders/stencil_mask.frag
@@ -0,0 +1,17 @@
+precision mediump float;
+varying vec2 v_texcoord;
+
+uniform vec2 half_size;
+uniform vec2 position;
+uniform float radius;
+
+void main() {
+    vec2 q = abs(gl_FragCoord.xy - position - half_size) - half_size + radius;
+    float dist = min(max(q.x,q.y), 0.0) + length(max(q, 0.0)) - radius;
+    float smoothedAlpha = 1.0 - smoothstep(-1.0, 0.5, dist);
+    gl_FragColor = mix(vec4(0.0), vec4(1.0), smoothedAlpha);
+
+    if (gl_FragColor.a < 1.0) {
+        discard;
+    }
+}