GCodeViewer -> Pass vertex normal to shaders for toolpaths

resources/shaders/toolpaths.fs

@@ -0,0 +1,31 @@
+#version 110
+
+// normalized values for (-0.6/1.31, 0.6/1.31, 1./1.31)
+const vec3 LIGHT_TOP_DIR = vec3(-0.4574957, 0.4574957, 0.7624929);
+const vec3 LIGHT_FRONT_DIR = vec3(0.0, 0.0, 1.0);
+
+// x = ambient, y = top diffuse, z = front diffuse, w = global
+uniform vec4 light_intensity;
+uniform vec3 uniform_color;
+
+varying vec3 eye_position;
+varying vec3 eye_normal;
+
+float intensity;
+
+void main()
+{
+    vec3 normal = normalize(eye_normal);
+
+    // Compute the cos of the angle between the normal and lights direction. The light is directional so the direction is constant for every vertex.
+    // Since these two are normalized the cosine is the dot product. Take the abs value to light the lines no matter in which direction the normal points.
+    float NdotL = abs(dot(normal, LIGHT_TOP_DIR));
+
+    intensity = light_intensity.x + NdotL * light_intensity.y;
+
+    // Perform the same lighting calculation for the 2nd light source.
+    NdotL = abs(dot(normal, LIGHT_FRONT_DIR));
+    intensity += NdotL * light_intensity.z;    
+
+    gl_FragColor = vec4(uniform_color * light_intensity.w * intensity, 1.0);
+}