diff --git a/vis/shaders/curve-stereo.gm.glsl b/vis/shaders/curve-stereo.gm.glsl
index 748a17b..c60b840 100644
--- a/vis/shaders/curve-stereo.gm.glsl
+++ b/vis/shaders/curve-stereo.gm.glsl
@@ -31,6 +31,7 @@ void main() {
     for (int i = 0; i < SUBS; i++) {
         vpos = mix(gpos[0], gpos[1], i * 1.0f / (SUBS - 1));
         vpos = normalize(vpos);
+
         gl_Position = proj * stereo(vpos);
         EmitVertex();
     }
diff --git a/vis/shaders/diffuse.fs.glsl b/vis/shaders/diffuse.fs.glsl
index ae05d4e..d8cc3fe 100644
--- a/vis/shaders/diffuse.fs.glsl
+++ b/vis/shaders/diffuse.fs.glsl
@@ -1,9 +1,14 @@
 #version 430
 
-in vec4 col;
+layout(location=1) in vec4 col;
+layout(location=2) in vec3 normal;
 
 out vec4 color;
 
 void main() {
+    float bright = dot(normal, normalize(vec3(-0.6, 1, 2)));
+    bright = .6 + .3 * bright;
+
     color = col;
+    color.xyz *= bright;
 }
diff --git a/vis/shaders/slice/slice.gm.glsl b/vis/shaders/slice/slice.gm.glsl
index a7c81d9..0bbda61 100644
--- a/vis/shaders/slice/slice.gm.glsl
+++ b/vis/shaders/slice/slice.gm.glsl
@@ -15,8 +15,9 @@ layout(std140, binding=1) uniform Matrices {
 in ivec4 vInds[];
 in vec4 vCol[];
 
-out vec4 pos;
-out vec4 col;
+layout(location=0) out vec4 pos;
+layout(location=1) out vec4 col;
+layout(location=2) out vec3 normal;
 
 out gl_PerVertex {
     vec4 gl_Position;
@@ -60,6 +61,17 @@ void main() {
         sect[S++] = mix(a, b, t);
     }
 
+    normal = cross(sect[1].xyz - sect[0].xyz, sect[2].xyz - sect[0].xyz);
+    normal = normalize(normal);
+
+    float r = dot(normal, sect[0].xyz);
+
+    if (abs(r) < 0.001)
+        r = dot(normal, sect[0].xyz + vec3(0, 0, 1));
+
+    if (r < 0)
+        normal *= -1;
+
     for (int s = 0; s < S; ++s) {
         emit(sect[s]);
     }
diff --git a/vis/shaders/solid.fs.glsl b/vis/shaders/solid.fs.glsl
index 11f3ec0..37b0d5a 100644
--- a/vis/shaders/solid.fs.glsl
+++ b/vis/shaders/solid.fs.glsl
@@ -7,6 +7,8 @@ in vec4 pos;
 out vec4 color;
 
 void main() {
+    if (pos.w > 0.8) discard;
+
     float d = smoothstep(-2, 2, pos.z);
     color = vec4(c * d, 1);
 }