Tech ENABLE_GL_SHADERS_ATTRIBUTES - Added shaders for glsl version 140

(cherry picked from commit prusa3d/PrusaSlicer@76d1d4949b)

resources/shaders/140/variable_layer_height.vs

@@ -0,0 +1,60 @@
+#version 140
+
+#define INTENSITY_CORRECTION 0.6
+
+const vec3 LIGHT_TOP_DIR = vec3(-0.4574957, 0.4574957, 0.7624929);
+#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.125 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SHININESS  20.0
+
+const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
+#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+//#define LIGHT_FRONT_SPECULAR (0.0 * INTENSITY_CORRECTION)
+//#define LIGHT_FRONT_SHININESS 5.0
+
+#define INTENSITY_AMBIENT    0.3
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+uniform mat3 normal_matrix;
+uniform mat4 volume_world_matrix;
+uniform float object_max_z;
+
+in vec3 v_position;
+in vec3 v_normal;
+in vec2 v_tex_coord;
+
+// x = tainted, y = specular;
+out vec2 intensity;
+
+out float object_z;
+
+void main()
+{
+	// =====================================================
+	// NOTE:
+	// when object_max_z > 0.0  we are rendering the overlay
+	// when object_max_z == 0.0 we are rendering the volumes
+	// =====================================================
+
+    // First transform the normal into camera space and normalize the result.
+    vec3 normal = (object_max_z > 0.0) ? vec3(0.0, 0.0, 1.0) : normalize(normal_matrix * v_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. We also need to clamp the result to the [0,1] range.
+    float NdotL = max(dot(normal, LIGHT_TOP_DIR), 0.0);
+
+    intensity.x = INTENSITY_AMBIENT + NdotL * LIGHT_TOP_DIFFUSE;
+    vec4 position = view_model_matrix * vec4(v_position, 1.0);
+    intensity.y = LIGHT_TOP_SPECULAR * pow(max(dot(-normalize(position.xyz), reflect(-LIGHT_TOP_DIR, normal)), 0.0), LIGHT_TOP_SHININESS);
+
+    // Perform the same lighting calculation for the 2nd light source (no specular)
+    NdotL = max(dot(normal, LIGHT_FRONT_DIR), 0.0);
+    
+    intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
+
+    // Scaled to widths of the Z texture.
+    object_z = (object_max_z > 0.0) ? object_max_z * v_tex_coord.y : (volume_world_matrix * vec4(v_position, 1.0)).z;
+        
+    gl_Position = projection_matrix * position;
+}