slideshow: Add back lighting in the SimpleTransition shaders

Change-Id: Iec854a8369a7a9f845f261233e46aea8097db109

slideshow/opengl/basicFragmentShader.glsl

@@ -30,10 +30,14 @@
 
 uniform sampler2D slideTexture;
 varying vec2 v_texturePosition;
+varying vec3 v_normal;
 
 void main() {
-     // TODO: handle lighting.
-     gl_FragColor = texture2D(slideTexture, v_texturePosition);
+    vec3 lightVector = vec3(0.0, 0.0, 1.0);
+    float light = max(dot(lightVector, v_normal), 0.0);
+    vec4 fragment = texture2D(slideTexture, v_texturePosition);
+    vec4 black = vec4(0.0, 0.0, 0.0, fragment.a);
+    gl_FragColor = mix(black, fragment, light);
 }
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

slideshow/opengl/basicVertexShader.glsl

@@ -29,11 +29,13 @@
 #version 120
 
 varying vec2 v_texturePosition;
+varying vec3 v_normal;
 
 void main( void )
 {
     gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
     v_texturePosition = gl_MultiTexCoord0.xy;
+    v_normal = normalize(gl_NormalMatrix * gl_Normal);
 }
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

slideshow/opengl/reflectionFragmentShader.glsl

@@ -31,9 +31,15 @@
 uniform sampler2D slideTexture;
 varying float v_isShadow;
 varying vec2 v_texturePosition;
+varying vec3 v_normal;
 
 void main() {
+    vec3 lightVector = vec3(0.0, 0.0, 1.0);
+    float light = max(dot(lightVector, v_normal), 0.0);
     vec4 fragment = texture2D(slideTexture, v_texturePosition);
+    vec4 black = vec4(0.0, 0.0, 0.0, fragment.a);
+    fragment = mix(black, fragment, light);
+
     if (v_isShadow > 0.5) {
         if (v_texturePosition.y > 1.0 - 0.3)
             gl_FragColor = mix(fragment, vec4(0.0, 0.0, 0.0, 0.0), (1.0 - v_texturePosition.y) / 0.3);

slideshow/opengl/reflectionVertexShader.glsl

@@ -28,13 +28,15 @@
 
 #version 130
 
-varying float v_isShadow;
 varying vec2 v_texturePosition;
+varying vec3 v_normal;
+varying float v_isShadow;
 
 void main( void )
 {
     gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
     v_texturePosition = gl_MultiTexCoord0.xy;
+    v_normal = normalize(gl_NormalMatrix * gl_Normal);
     v_isShadow = float(gl_VertexID >= 6);
 }