curved normal

src/shaders/grassFragment.glsl

@@ -4,13 +4,21 @@ uniform float time;
 
 uniform vec3 lightDirection;
 
+in vec3 vPosition;
+
 in mat4 normalMatrix;
-in vec3 vNormal;
+in vec3 vNormal1;
+in vec3 vNormal2;
 
 void main() {
     vec3 finalColor = vec3(0.0, 0.4, 0.0);
 
-    vec3 normalW = normalize((normalMatrix * vec4(vNormal, 0.0)).xyz);
+    float normalBlending = vPosition.x + 0.5;
+
+    vec3 normal = mix(vNormal1, vNormal2, normalBlending);
+    normal = normalize(normal);
+
+    vec3 normalW = normalize((normalMatrix * vec4(normal, 0.0)).xyz);
 
     float ndl1 = max(dot(normalW, lightDirection), 0.0);
     float ndl2 = max(dot(-normalW, lightDirection), 0.0);

src/shaders/grassVertex.glsl

@@ -5,8 +5,11 @@ attribute vec3 normal;
 
 uniform mat4 viewProjection;
 
+out vec3 vPosition;
+
 out mat4 normalMatrix;
-out vec3 vNormal;
+out vec3 vNormal1;
+out vec3 vNormal2;
 
 // rotation using https://www.wikiwand.com/en/Rodrigues%27_rotation_formula
 vec3 rotateAround(vec3 vector, vec3 axis, float theta) {
@@ -19,14 +22,26 @@ vec3 rotateAround(vec3 vector, vec3 axis, float theta) {
 void main() {
     #include<instancesVertex>
 
+    // curvy normal
+    float normalCurveAmount = 0.3 * 3.14;
+    vec3 curvyNormal1 = rotateAround(normal, vec3(0.0, 1.0, 0.0), normalCurveAmount);
+    vec3 curvyNormal2 = rotateAround(normal, vec3(0.0, 1.0, 0.0), -normalCurveAmount);
+
+    // curved grass blade
     float leanAmount = 0.3;
     float curveAmount = leanAmount * position.y;
-    vec3 rotatedPosition = rotateAround(position, vec3(1.0, 0.0, 0.0), curveAmount);
-    vec3 rotatedNormal = rotateAround(normal, vec3(1.0, 0.0, 0.0), curveAmount);
+    vec3 leaningPosition = rotateAround(position, vec3(1.0, 0.0, 0.0), curveAmount);
+
+    vec3 leaningNormal1 = rotateAround(curvyNormal1, vec3(1.0, 0.0, 0.0), curveAmount);
+    vec3 leaningNormal2 = rotateAround(curvyNormal2, vec3(1.0, 0.0, 0.0), curveAmount);
 
-    vec4 outPosition = viewProjection * finalWorld * vec4(rotatedPosition, 1.0);
+    vec4 outPosition = viewProjection * finalWorld * vec4(leaningPosition, 1.0);
     gl_Position = outPosition;
 
+    vPosition = position;
+
     normalMatrix = transpose(inverse(finalWorld));
-    vNormal = rotatedNormal;
+
+    vNormal1 = leaningNormal1;
+    vNormal2 = leaningNormal2;
 }