Tech ENABLE_LEGACY_OPENGL_REMOVAL - porting remaining changes

(cherry picked from commit prusa3d/PrusaSlicer@2f572d3cf0 )

resources/shaders/background_attr.vs

@@ -0,0 +1,12 @@
+#version 110
+
+attribute vec3 v_position;
+attribute vec2 v_tex_coord;
+
+varying vec2 tex_coord;
+
+void main()
+{
+	tex_coord = v_tex_coord;
+    gl_Position = vec4(v_position, 1.0);
+}

resources/shaders/cali.fs

@@ -1,8 +0,0 @@
-#version 110
-
-uniform vec4 uniform_color;
-
-void main()
-{
-    gl_FragColor = uniform_color;
-}

resources/shaders/cali.vs

@@ -1,6 +0,0 @@
-#version 110
-
-void main()
-{
-    gl_Position = ftransform();
-}

resources/shaders/flat_attr.vs

@@ -2,9 +2,10 @@
 
 attribute vec3 v_position;
 
-uniform mat4 projection_view_model_matrix;
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
 
 void main()
 {
-    gl_Position = projection_view_model_matrix * vec4(v_position, 1.0);
+    gl_Position = projection_matrix * view_model_matrix * vec4(v_position, 1.0);
 }

resources/shaders/flat_texture_attr.vs

@@ -0,0 +1,15 @@
+#version 110
+
+attribute vec3 v_position;
+attribute vec2 v_tex_coord;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+
+varying vec2 tex_coord;
+
+void main()
+{
+	tex_coord = v_tex_coord;
+    gl_Position = projection_matrix * view_model_matrix * vec4(v_position, 1.0);
+}

resources/shaders/gouraud.fs

@@ -48,7 +48,6 @@ varying vec2 intensity;
 
 uniform PrintVolumeDetection print_volume;
 
-varying vec4 model_pos;
 varying vec4 world_pos;
 varying float world_normal_z;
 varying vec3 eye_normal;

resources/shaders/gouraud.vs

@@ -38,7 +38,6 @@ varying vec2 intensity;
 
 varying vec3 clipping_planes_dots;
 
-varying vec4 model_pos;
 varying vec4 world_pos;
 varying float world_normal_z;
 varying vec3 eye_normal;
@@ -60,7 +59,6 @@ void main()
 	NdotL = max(dot(eye_normal, LIGHT_FRONT_DIR), 0.0);
 	intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
 
-    model_pos = gl_Vertex;
     // Point in homogenous coordinates.
     world_pos = volume_world_matrix * gl_Vertex;
 

resources/shaders/gouraud_attr.vs

@@ -0,0 +1,77 @@
+#version 110
+
+#define INTENSITY_CORRECTION 0.6
+
+// 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);
+#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.125 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SHININESS  20.0
+
+// normalized values for (1./1.43, 0.2/1.43, 1./1.43)
+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
+
+const vec3 ZERO = vec3(0.0, 0.0, 0.0);
+
+struct SlopeDetection
+{
+    bool actived;
+	float normal_z;
+    mat3 volume_world_normal_matrix;
+};
+
+attribute vec3 v_position;
+attribute vec3 v_normal;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+uniform mat3 normal_matrix;
+uniform mat4 volume_world_matrix;
+uniform SlopeDetection slope;
+
+// Clipping plane, x = min z, y = max z. Used by the FFF and SLA previews to clip with a top / bottom plane.
+uniform vec2 z_range;
+// Clipping plane - general orientation. Used by the SLA gizmo.
+uniform vec4 clipping_plane;
+
+// x = diffuse, y = specular;
+varying vec2 intensity;
+
+varying vec3 clipping_planes_dots;
+
+varying vec4 world_pos;
+varying float world_normal_z;
+varying vec3 eye_normal;
+
+void main()
+{
+	// First transform the normal into camera space and normalize the result.
+    eye_normal = 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(eye_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, eye_normal)), 0.0), LIGHT_TOP_SHININESS);
+
+	// Perform the same lighting calculation for the 2nd light source (no specular applied).
+	NdotL = max(dot(eye_normal, LIGHT_FRONT_DIR), 0.0);
+	intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
+
+    // Point in homogenous coordinates.
+    world_pos = volume_world_matrix * vec4(v_position, 1.0);
+
+    // z component of normal vector in world coordinate used for slope shading
+    world_normal_z = slope.actived ? (normalize(slope.volume_world_normal_matrix * v_normal)).z : 0.0;
+
+    gl_Position = projection_matrix * position;
+    // Fill in the scalars for fragment shader clipping. Fragments with any of these components lower than zero are discarded.
+    clipping_planes_dots = vec3(dot(world_pos, clipping_plane), world_pos.z - z_range.x, z_range.y - world_pos.z);
+}

resources/shaders/gouraud_light_attr.vs

@@ -0,0 +1,45 @@
+#version 110
+
+#define INTENSITY_CORRECTION 0.6
+
+// 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);
+#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.125 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SHININESS  20.0
+
+// normalized values for (1./1.43, 0.2/1.43, 1./1.43)
+const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
+#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+
+#define INTENSITY_AMBIENT    0.3
+
+attribute vec3 v_position;
+attribute vec3 v_normal;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+uniform mat3 normal_matrix;
+
+// x = tainted, y = specular;
+varying vec2 intensity;
+
+void main()
+{
+    // First transform the normal into camera space and normalize the result.
+    vec3 normal = 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 applied).
+    NdotL = max(dot(normal, LIGHT_FRONT_DIR), 0.0);
+    intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
+
+    gl_Position = projection_matrix * position;
+}

resources/shaders/gouraud_light_instanced_attr.vs

@@ -0,0 +1,50 @@
+#version 110
+
+#define INTENSITY_CORRECTION 0.6
+
+// 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);
+#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.125 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SHININESS  20.0
+
+// normalized values for (1./1.43, 0.2/1.43, 1./1.43)
+const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
+#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+
+#define INTENSITY_AMBIENT    0.3
+
+// vertex attributes
+attribute vec3 v_position;
+attribute vec3 v_normal;
+// instance attributes
+attribute vec3 i_offset;
+attribute vec2 i_scales;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+uniform mat3 normal_matrix;
+
+// x = tainted, y = specular;
+varying vec2 intensity;
+
+void main()
+{
+    // First transform the normal into camera space and normalize the result.
+    vec3 eye_normal = 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(eye_normal, LIGHT_TOP_DIR), 0.0);
+
+    intensity.x = INTENSITY_AMBIENT + NdotL * LIGHT_TOP_DIFFUSE;
+    vec4 world_position = vec4(v_position * vec3(vec2(1.5 * i_scales.x), 1.5 * i_scales.y) + i_offset - vec3(0.0, 0.0, 0.5 * i_scales.y), 1.0);
+    vec4 eye_position = view_model_matrix * world_position;
+    intensity.y = LIGHT_TOP_SPECULAR * pow(max(dot(-normalize(eye_position.xyz), reflect(-LIGHT_TOP_DIR, eye_normal)), 0.0), LIGHT_TOP_SHININESS);
+
+    // Perform the same lighting calculation for the 2nd light source (no specular applied).
+    NdotL = max(dot(eye_normal, LIGHT_FRONT_DIR), 0.0);
+    intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
+
+    gl_Position = projection_matrix * eye_position;
+}

resources/shaders/mm_contour_attr.fs

@@ -0,0 +1,13 @@
+#version 110
+
+const float EPSILON = 0.0001;
+
+uniform vec4 uniform_color;
+
+void main()
+{
+    gl_FragColor = uniform_color;
+    // Values inside depth buffer for fragments of the contour of a selected area are offset
+    // by small epsilon to solve z-fighting between painted triangles and contour lines.
+    gl_FragDepth = gl_FragCoord.z - EPSILON;
+}

resources/shaders/mm_contour_attr.vs

@@ -0,0 +1,11 @@
+#version 110
+
+attribute vec3 v_position;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+
+void main()
+{
+    gl_Position = projection_matrix * view_model_matrix * vec4(v_position, 1.0);
+}

resources/shaders/mm_gouraud_attr.fs

@@ -0,0 +1,90 @@
+#version 110
+
+#define INTENSITY_CORRECTION 0.6
+
+// 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);
+#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.125 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SHININESS  20.0
+
+// normalized values for (1./1.43, 0.2/1.43, 1./1.43)
+const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
+#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+
+#define INTENSITY_AMBIENT    0.3
+
+const vec3  ZERO    = vec3(0.0, 0.0, 0.0);
+const float EPSILON = 0.0001;
+//BBS: add grey and orange
+//const vec3 GREY = vec3(0.9, 0.9, 0.9);
+const vec3 ORANGE = vec3(0.8, 0.4, 0.0);
+const vec3 LightRed = vec3(0.78, 0.0, 0.0);
+const vec3 LightBlue = vec3(0.73, 1.0, 1.0);
+uniform vec4 uniform_color;
+
+uniform bool volume_mirrored;
+
+uniform mat4 view_model_matrix;
+uniform mat3 normal_matrix;
+
+varying vec3 clipping_planes_dots;
+varying vec4 model_pos;
+varying vec4 world_pos;
+
+struct SlopeDetection
+{
+    bool actived;
+	 float normal_z;
+    mat3 volume_world_normal_matrix;
+};
+uniform SlopeDetection slope;
+
+void main()
+{
+    if (any(lessThan(clipping_planes_dots, ZERO)))
+        discard;
+    vec3  color = uniform_color.rgb;
+    float alpha = uniform_color.a;
+
+    vec3 triangle_normal = normalize(cross(dFdx(model_pos.xyz), dFdy(model_pos.xyz)));
+#ifdef FLIP_TRIANGLE_NORMALS
+    triangle_normal = -triangle_normal;
+#endif
+
+    if (volume_mirrored)
+        triangle_normal = -triangle_normal;
+
+    vec3 transformed_normal = normalize(slope.volume_world_normal_matrix * triangle_normal);
+     
+    if (slope.actived) {
+        if(world_pos.z<0.1&&world_pos.z>-0.1)
+         {
+              color = LightBlue;
+              alpha = 1.0;
+         }
+         else if( transformed_normal.z < slope.normal_z - EPSILON)
+        {
+            color = color * 0.5 + LightRed * 0.5;
+            alpha = 1.0;
+        }
+    }
+    // First transform the normal into camera space and normalize the result.
+    vec3 eye_normal = normalize(normal_matrix * triangle_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(eye_normal, LIGHT_TOP_DIR), 0.0);
+
+    // x = diffuse, y = specular;
+    vec2 intensity = vec2(0.0);
+    intensity.x = INTENSITY_AMBIENT + NdotL * LIGHT_TOP_DIFFUSE;
+    vec3 position = (view_model_matrix * model_pos).xyz;
+    intensity.y = LIGHT_TOP_SPECULAR * pow(max(dot(-normalize(position), reflect(-LIGHT_TOP_DIR, eye_normal)), 0.0), LIGHT_TOP_SHININESS);
+
+    // Perform the same lighting calculation for the 2nd light source (no specular applied).
+    NdotL = max(dot(eye_normal, LIGHT_FRONT_DIR), 0.0);
+    intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
+
+    gl_FragColor = vec4(vec3(intensity.y) + color * intensity.x, alpha);
+}

resources/shaders/mm_gouraud_attr.vs

@@ -0,0 +1,35 @@
+#version 110
+
+const vec3 ZERO = vec3(0.0, 0.0, 0.0);
+
+attribute vec3 v_position;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+
+uniform mat4 volume_world_matrix;
+// Clipping plane, x = min z, y = max z. Used by the FFF and SLA previews to clip with a top / bottom plane.
+uniform vec2 z_range;
+// Clipping plane - general orientation. Used by the SLA gizmo.
+uniform vec4 clipping_plane;
+
+varying vec3 clipping_planes_dots;
+varying vec4 model_pos;
+varying vec4 world_pos;
+struct SlopeDetection
+{
+    bool actived;
+	float normal_z;
+    mat3 volume_world_normal_matrix;
+};
+uniform SlopeDetection slope;
+void main()
+{
+    model_pos = vec4(v_position, 1.0);
+    // Point in homogenous coordinates.
+    world_pos = volume_world_matrix * model_pos;
+
+    gl_Position = projection_matrix * view_model_matrix * model_pos;
+    // Fill in the scalars for fragment shader clipping. Fragments with any of these components lower than zero are discarded.
+    clipping_planes_dots = vec3(dot(world_pos, clipping_plane), world_pos.z - z_range.x, z_range.y - world_pos.z);
+}

resources/shaders/options_110.fs

@@ -1,8 +0,0 @@
-#version 110
-
-uniform vec4 uniform_color;
-
-void main()
-{
-    gl_FragColor = uniform_color;
-}

resources/shaders/options_110.vs

@@ -1,22 +0,0 @@
-#version 110
-
-uniform bool use_fixed_screen_size;
-uniform float zoom;
-uniform float point_size;
-uniform float near_plane_height;
-
-float fixed_screen_size()
-{
-    return point_size;
-}
-
-float fixed_world_size()
-{
-    return (gl_Position.w == 1.0) ? zoom * near_plane_height * point_size : near_plane_height * point_size / gl_Position.w;
-}
-
-void main()
-{
-    gl_Position = ftransform();
-    gl_PointSize = use_fixed_screen_size ? fixed_screen_size() : fixed_world_size();
-}

resources/shaders/options_120.fs

@@ -1,22 +0,0 @@
-// version 120 is needed for gl_PointCoord
-#version 120
-
-uniform vec4 uniform_color;
-uniform float percent_outline_radius;
-uniform float percent_center_radius;
-
-vec4 calc_color(float radius, vec4 color)
-{
-    return ((radius < percent_center_radius) || (radius > 1.0 - percent_outline_radius)) ?
-            vec4(0.5 * color.rgb, color.a) : color;
-}
-
-void main()
-{
-    vec2 pos = (gl_PointCoord - 0.5) * 2.0;
-    float radius = length(pos);
-    if (radius > 1.0)
-        discard;
-
-    gl_FragColor = calc_color(radius, uniform_color);
-}

resources/shaders/options_120.vs

@@ -1,22 +0,0 @@
-#version 120
-
-uniform bool use_fixed_screen_size;
-uniform float zoom;
-uniform float point_size;
-uniform float near_plane_height;
-
-float fixed_screen_size()
-{
-    return point_size;
-}
-
-float fixed_world_size()
-{
-    return (gl_Position.w == 1.0) ? zoom * near_plane_height * point_size : near_plane_height * point_size / gl_Position.w;
-}
-
-void main()
-{
-    gl_Position = ftransform();
-    gl_PointSize = use_fixed_screen_size ? fixed_screen_size() : fixed_world_size();
-}

resources/shaders/printbed.fs

@@ -7,15 +7,15 @@ uniform sampler2D texture;
 uniform bool transparent_background;
 uniform bool svg_source;
 
-varying vec2 tex_coords;
+varying vec2 tex_coord;
 
 vec4 svg_color()
 {
     // takes foreground from texture
-    vec4 fore_color = texture2D(texture, tex_coords);
+    vec4 fore_color = texture2D(texture, tex_coord);
 
     // calculates radial gradient
-    vec3 back_color = vec3(mix(back_color_light, back_color_dark, smoothstep(0.0, 0.5, length(abs(tex_coords.xy) - vec2(0.5)))));
+    vec3 back_color = vec3(mix(back_color_light, back_color_dark, smoothstep(0.0, 0.5, length(abs(tex_coord.xy) - vec2(0.5)))));
 
     // blends foreground with background
     return vec4(mix(back_color, fore_color.rgb, fore_color.a), transparent_background ? fore_color.a : 1.0);
@@ -24,7 +24,7 @@ vec4 svg_color()
 vec4 non_svg_color()
 {
     // takes foreground from texture
-    vec4 color = texture2D(texture, tex_coords);
+    vec4 color = texture2D(texture, tex_coord);
     return vec4(color.rgb, transparent_background ? color.a * 0.25 : color.a);
 }
 

resources/shaders/printbed.vs

@@ -1,9 +1,9 @@
 #version 110
 
-varying vec2 tex_coords;
+varying vec2 tex_coord;
 
 void main()
 {
     gl_Position = ftransform();
-	tex_coords = gl_MultiTexCoord0.xy;
+	tex_coord = gl_MultiTexCoord0.xy;
 }

resources/shaders/printbed_attr.vs

@@ -0,0 +1,15 @@
+#version 110
+
+attribute vec3 v_position;
+attribute vec2 v_tex_coord;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+
+varying vec2 tex_coord;
+
+void main()
+{
+	tex_coord = v_tex_coord;
+    gl_Position = projection_matrix * view_model_matrix * vec4(v_position, 1.0);
+}

resources/shaders/thumbnail_attr.vs

@@ -0,0 +1,51 @@
+#version 110
+
+#define INTENSITY_CORRECTION 0.6
+
+// 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);
+#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.125 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SHININESS  20.0
+
+// normalized values for (1./1.43, 0.2/1.43, 1./1.43)
+const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
+#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+
+#define INTENSITY_AMBIENT    0.3
+
+attribute vec3 v_position;
+attribute vec3 v_normal;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+uniform mat3 normal_matrix;
+
+uniform mat4 volume_world_matrix;
+
+// x = tainted, y = specular;
+varying vec2 intensity;
+varying vec4 world_pos;
+
+void main()
+{
+    // First transform the normal into camera space and normalize the result.
+    vec3 normal = 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 applied).
+    NdotL = max(dot(normal, LIGHT_FRONT_DIR), 0.0);
+    intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
+
+    // Point in homogenous coordinates.
+    world_pos = volume_world_matrix * gl_Vertex;
+
+    gl_Position = projection_matrix * position;
+}

resources/shaders/variable_layer_height_attr.vs

@@ -0,0 +1,60 @@
+#version 110
+
+#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
+
+attribute vec3 v_position;
+attribute vec3 v_normal;
+attribute vec2 v_tex_coord;
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+uniform mat3 normal_matrix;
+uniform mat4 volume_world_matrix;
+uniform float object_max_z;
+
+// x = tainted, y = specular;
+varying vec2 intensity;
+
+varying 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;
+}