as per request spotlight example (#1146)

Co-authored-by: codifies <nospam@antispam.com>

examples/shaders/resources/shaders/glsl100/spotlight.fs

@@ -0,0 +1,52 @@
+#version 100
+
+precision mediump float;
+
+#define     MAX_SPOTS			4
+#define		RADIUS				256.0
+#define		INNER				200.0
+
+// Inputs
+// array of spotlight positions
+uniform vec2 spots[MAX_SPOTS];
+
+uniform float screenWidth; // width of the screen
+
+void main()
+{
+
+	float alpha;
+	// get the position of the current fragment (screen coordinates!)
+	vec2 pos = vec2(gl_FragCoord.x, gl_FragCoord.y);
+
+	
+	// find out which spotlight is nearest
+	float d = 65000.0; // some high value
+	float di = 0.0;
+
+    for (int i = 0; i < MAX_SPOTS; i++)
+    {
+		di = distance(pos, spots[i]);
+		if (d > di) d = di;
+    }
+    
+    // d now equals distance to nearest spot...
+    if (d > RADIUS) {
+		alpha = 1.0;
+	} else {
+		if (d < INNER) {
+			alpha = 0.0;
+		} else {
+			alpha = (d - INNER) / (RADIUS - INNER);
+		}
+	}
+	
+	// right hand side of screen is dimly lit, could make the
+	// threshold value user definable.
+	if (pos.x > screenWidth/2.0 && alpha > 0.9) {
+		alpha = 0.9;
+	}
+
+	// could make the black out colour user definable...
+    gl_FragColor = vec4( 0, 0, 0, alpha);
+}

examples/shaders/resources/shaders/glsl330/spotlight.fs

@@ -0,0 +1,53 @@
+#version 330
+
+// Output fragment color
+out vec4 finalColor;
+
+#define     MAX_SPOTS			4
+#define		RADIUS				256
+#define		INNER				200
+
+// Inputs
+// array of spotlight positions
+uniform vec2 spots[MAX_SPOTS];
+
+uniform float screenWidth; // width of the screen
+
+void main()
+{
+
+	float alpha;
+	// get the position of the current fragment (screen coordinates!)
+	vec2 pos = vec2(gl_FragCoord.x, gl_FragCoord.y);
+
+	
+	// find out which spotlight is nearest
+	float d = 65000; // some high value
+	float di = 0;
+
+    for (int i = 0; i < MAX_SPOTS; i++)
+    {
+		di = distance(pos, spots[i]);
+		if (d > di) d = di;
+    }
+    
+    // d now equals distance to nearest spot...
+    if (d > RADIUS) {
+		alpha = 1.0;
+	} else {
+		if (d < INNER) {
+			alpha = 0.0;
+		} else {
+			alpha = (d - INNER) / (RADIUS - INNER);
+		}
+	}
+	
+	// right hand side of screen is dimly lit, could make the
+	// threshold value user definable.
+	if (pos.x>screenWidth/2.0 && alpha >0.9) {
+		alpha = 0.9;
+	}
+
+	// could make the black out colour user definable...
+    finalColor = vec4( 0, 0, 0, alpha);
+}