1 files changed, 21 insertions, 9 deletions

diff --git a/resources/shaders/gouraud.vs b/resources/shaders/gouraud.vs
index cc54c1c44..ed7e3f56b 100644
--- a/resources/shaders/gouraud.vs
+++ b/resources/shaders/gouraud.vs
@@ -20,13 +20,21 @@ const vec3 ZERO = vec3(0.0, 0.0, 0.0);
 
 struct PrintBoxDetection
 {
+    bool actived;
     vec3 min;
     vec3 max;
-    bool volume_detection;
     mat4 volume_world_matrix;
 };
 
+struct SlopeDetection
+{
+    bool actived;
+	float normal_z;
+    mat3 volume_world_normal_matrix;
+};
+
 uniform PrintBoxDetection print_box;
+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;
@@ -41,27 +49,28 @@ varying vec3 delta_box_max;
 
 varying vec3 clipping_planes_dots;
 
+varying float world_normal_z;
+varying vec3 eye_normal;
+
 void main()
 {
     // First transform the normal into camera space and normalize the result.
-    vec3 normal = normalize(gl_NormalMatrix * gl_Normal);
+    eye_normal = normalize(gl_NormalMatrix * gl_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);
+    float NdotL = max(dot(eye_normal, LIGHT_TOP_DIR), 0.0);
 
     intensity.x = INTENSITY_AMBIENT + NdotL * LIGHT_TOP_DIFFUSE;
-    intensity.y = 0.0;
-
-    if (NdotL > 0.0)
-        intensity.y += LIGHT_TOP_SPECULAR * pow(max(dot(normal, reflect(-LIGHT_TOP_DIR, normal)), 0.0), LIGHT_TOP_SHININESS);
+    vec3 position = (gl_ModelViewMatrix * gl_Vertex).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(normal, LIGHT_FRONT_DIR), 0.0);
+    NdotL = max(dot(eye_normal, LIGHT_FRONT_DIR), 0.0);
     intensity.x += NdotL * LIGHT_FRONT_DIFFUSE;
 
     // compute deltas for out of print volume detection (world coordinates)
-    if (print_box.volume_detection)
+    if (print_box.actived)
     {
         vec3 v = (print_box.volume_world_matrix * gl_Vertex).xyz;
         delta_box_min = v - print_box.min;
@@ -73,6 +82,9 @@ void main()
         delta_box_max = ZERO;
     }
 
+    // z component of normal vector in world coordinate used for slope shading
+	world_normal_z = slope.actived ? (normalize(slope.volume_world_normal_matrix * gl_Normal)).z : 0.0;
+
     gl_Position = ftransform();
     // Point in homogenous coordinates.
     vec4 world_pos = print_box.volume_world_matrix * gl_Vertex;